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jas11n
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PostPosted: Sun Nov 23, 2008 1:34 pm Reply with quote Back to top

OK, a run-through of replacing bulbs in various switches through out the car.
Most of the upper centre console switches have easily replaceable bulbs, just remove the front, pull out the old bulb and replace with a new one.
The 5mm wedge bulbs can be gotten hold of at a lot of places, but they can be expensive, so shop around.
If you search ebay for "5mm fruit machine bulbs" you'll see you can have a lot of them for a lot less than some outlets will charge you for a few.

Some of the later switches that had easily replaceable bulbs, changed very late in the series 4 (B4) 80's and the late Coupés and Cabriolets. As the picture below states from Audi, they can't be changed, but as we all know, anything can be changed if you put your mind to it, so ignore "A" in the picture below. Pfft, Audi didn't bank on the determination of it's buyers not wanting to pay silly money for a switch that has only lost it's illumination.

I'll add more parts to this thread as I take pictures. If you have a quattro and the illumination has gone in the difflock switch, these can be replaced too. I've replaced them in a few for myself and other people, but never thought to take pictures. So unless I get another to do a run-through on, or take mine out just to replace bulbs that haven't gone, then we'll have to wait for that.

Code:
If you have "any" switch that has dead illumination (including ambient temperature displays and automatic gear indicators), PM me, I can do this for you, I don't want paying, all I ask is you cover postage both ways.






Right, a lot of run-through are and have been, on www.20v.org for years, but there are no pictures included in the descriptions. This is what this thread is about. A picture paints a thousand words.

1/ Headlamp level switch bulb replacement

I thought this particular run through was on 20v.org, but that's for the seat heater switches which are very different inside (there's two seat heater switches, both different inside to each other as well, more on those later)

Anyhow. Here we go.

Remove the switch from the car.
Set yourself up somewhere with plenty of light and space, tie the other half up and gag her, then lock the dog away. It's a fiddly little bugger and you could do without distractions.



Remove the front off the switch.



You'll need to get a couple of small screwdrivers and lift the main black body of the switch up at the rear over the tangs, then slide the internals out from the rear. The two small spring clips on the side will fall out too. Just note how they are in there first off.




Now you need to pry out the black piece on the side, it just slides out upwards.




Now flip it over. You'll note everything is soldered on on the topside, not underneath like most PCB's.
The red arrows point to the legs that come through from the main red reflector. They are knurled over. I used a knife the cut the knurled part off each leg. Later when it's put back together, there's no problem of it coming loose as it's inside the main body of the switch. Also note the bulbs legs poking through (green arrows)



Now you need to flip it back over the other side, and carefully remove the red reflector straight up. BE CAREFUL here, see the small indentations around the top of the rotary wheel. On the underside of the red reflector is a small ball bearing that slots in these small indentations, making the wheel stop at each position you select when adjusting the lights.
Again, BE CAREFUL, you don't want to lose it.




Now you can see the bulb



I chose to use another bulb instead of replacing with a longer lasting LED. Reason? this switch seems to need it's illumination to come from the side. an LED is fussy in that it's very one directional in it's aim, in this case straight up. I used a 5mm wedge bulb that are used in some of the other dash switch, the ashtray light, the aux gauge lights and cig lighter etc.
Just bend out the folded over legs.
Here's the old bulb insoldered and the new one in place and checked to make sure it was lighting up.
Quote:
I have since removed and replaced this bulb with a 3mm >>> BT43W bulb from Maplins, I didn't have any during this run-through is all







Now reassemble everything, to stop the tiny ball bearing from falling out when upside down, I used a tiny little speck of grease to hold it in it's little seat.
Again, checked to make sure it was all ok.



Excuse poor picture, my camera will not focus very well in the dark



2/ Electric window switch LED replacement.

Now we've seen this question asked loads of times before, "how do you remove the inner door handle??" plenty of great explanations on here, but I can't remember coming across some good pictures documenting the process. So here's some of actually removing the inner door handle to gain access for removal of both the window switches and the mirror switch. [note, this is a Coupe inner door handle, other models differ]

Underneath the handle are three holes. The top and middle holes (number 1 & 2) contain an Allen headed bolt (some cars may have a torx headed bolt). You need a 4mm allen key, insert it up through the hole and fish about until you feel the allen key engage the bolt. Un-tighten them, not all the way as they are just clamps that clamp onto a bracket behind. Number 3 hole contains a pozi-headed screw, you need to remove this all the way out.




Pull the handle away from the door card and slide out the switch panel;



The window switch plate and the mirror switch plate are slide locked together, just simply slide them apart, either way, doesn't matter.



Unplug the various multiplugs from the rear depending on which switch you need to do. [You'll probably be wondering why I've got four window switches on a Coupé, that's because I have electric opening rear windows in my S2 Coupe.]



Take your switches inside, again you need a well lit area with no distractions, moaning partners, wild dogs/cats or hyperactive kids.

The switch plate and switch I had spare after fitting opening rear windows to the S2 a couple of months back.
The S2's four switches are all working fine, nice and shiny bright, but I still wanted to see how these things are put together. I like to mess Very Happy



So, after you've removed the switch plate from the door, you then need to remove the switch itself. Flip it over and get a blade down the side of the switch, push the switch down from the top side and it'll come out. It can be tight.




Now you need to remove the rocker plate on the top. Again get a blade and slide it down the side, not very far, but just enough so you see one side pop up.




Note for reference later, the earth terminal is number 3 and the 12v illumination terminal is number 4. You'll need to know this to get the correct polarity of the LED. The anode (12v in) is the longer leg of the LED, the cathode (earth) is the shorter leg of the LED.



Now you need to get the internal workings out of the switch body. There's four tabs on the inner plastic, that are snapped behind four tabs on the inside of the black body. You need to use something like some small terminal drivers to raise the black switch body up and carefully start to push the switch down from the top (or pull from the terminals at the bottom.) Don't lose heart, it comes out eventually.




All out and ready for surgery;




Here's the replacement LED. It's a 3mm 12v superbright LED from Maplins (the same LED I use to replace peoples outside temp gauge illumination) It has an inbuilt resistor too. Link to the code from Maplins >>> CJ70M



Now I first off roughly copied the shape the original LED's legs had been bent too;



Removed the old LED and it's resistor, then soldered on the new one. REMEMBER to get the polarity right, short leg to earth.



Once both legs had been soldered on, I checked it was ok with a 12v power source;



Then reassembled the the switch making sure the LED was lined up right;




Don't forget when refitting the rocker plate, to get it the right way round, the white protrusion on it's underside goes to the LED end;



Recheck to make sure it's looking ok;



Done, reverse removal to fit the switch back in the switch plate, then back out to the car to refit it.

3/ Mirror switch bulb replacement

Again, take the parts you need into the house/garage/where ever.
If your other half is up for it again, tie her up, gag her and remove all pets/children etc.

Here's the switch still in it's plate.



To remove, pull back on the two spring loaded hooks and get a blade down between the switch and the plate at the opposite end, push from the control side and out it pops.




There's six tangs on the inner switch body holding it into the black outer casing. I carefully got a blade in where each tang is, then inserted a straightened paper clip to stop it snapping back. Did this on all six, then pulled back on the two spring loaded hooks again and withdrew the internal switch casing upwards.





Make sure to leave the black switch body facing down (control buttons down) Once the innards come out you'll see why. There's two ball bearings which you don't want to lose. Put the black body to one side, it's not needed until you come to reassemble.



This what you are left with;




You need to lift up and remove the rubber cover which will expose the bulbs fully.



Now you need to separate the curcuit board away from the white plastic casing, just push the legs of the terminals out and they come apart.




Here the points on the PCB which you need to de-solder and withdraw the old bulbs from the other side. Old bulbs removed.




Again, I choose this time to reuse filament bulbs, I'm not sure if the 3mm LED's would be bright enough, even though they are SB versions.
The bulbs are again from Maplins, code >>> BT43W.
They are a small wire terminal bulb, 12v 60mA and are perfect size for size replacement. I've used these in difflock, ATD and heated seat switch replacements.



New bulbs soldered on.



Then use a 12v power source to check you've made good solder joints,



Reassembly is just a reverse of removal, REMEMBER not to turn the black casing upside down, you may lose those ball bearings.
One last check to make sure reassembly didn't undo your hard work.



Then go back to the car and refit it.

Should now look like this. "Note" Dunno why, but I thought the two direction buttons were illuminated, but apparently not. The white "L" and "R" symbols are just painted on. Funny how you have a preconception about things Laughing





Next up, seat heater switches. Working on those now.

Jase..
Wink

_________________
2001 Avus Silver RS4.
2004 A4 Avant 1.8T quattro Sport LE..

1995 S2 Coupe - sold
1995 A6 Avant TDi - sold
1993 80 TDi - sold
1990 90 2.3 auto - scrapped
1989 Coupe 2.3e - sold
1990 cq20v - sold
1990 80 2.8 quattro - sold 
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PostPosted: Sun Nov 23, 2008 2:28 pm Reply with quote Back to top

exellent write ups,i`ve done all the ones you`ve covered with no probs,well once you get the hang of taking them apart.

i`m just left with the diff switch and was wanting to know if it`s just the bt43w bulbs that`s inside or is there any led bulbs.the only bit that lights up is the diff lettering. cheers

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PostPosted: Sun Nov 23, 2008 2:39 pm Reply with quote Back to top

taylormade wrote:
exellent write ups,i`ve done all the ones you`ve covered with no probs,well once you get the hang of taking them apart.

i`m just left with the diff switch and was wanting to know if it`s just the bt43w bulbs that`s inside or is there any led bulbs.the only bit that lights up is the diff lettering. cheers


Can be either Rory, most had bulbs (BT43W type are ideal) and some of the very last had LED's. I've yet to come across an LED version so can't say 100% what LED's to use to replace.

Jase..
Wink

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2001 Avus Silver RS4.
2004 A4 Avant 1.8T quattro Sport LE..

1995 S2 Coupe - sold
1995 A6 Avant TDi - sold
1993 80 TDi - sold
1990 90 2.3 auto - scrapped
1989 Coupe 2.3e - sold
1990 cq20v - sold
1990 80 2.8 quattro - sold 
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PostPosted: Sun Nov 23, 2008 2:47 pm Reply with quote Back to top

thanks, bt43w bulbs is all i got left. Wink

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PostPosted: Sun Nov 23, 2008 3:10 pm Reply with quote Back to top

Best to replace all of them. 1/ you may get the new brighter than the old, and 2/ sods law says others will go just after you've done it.
Three needed, one of them is a bit of a pain, it sits inside a tube. Easiest is to get a matchstick and superglue to the exposed top of the bulb, desolder and pull it out.

Wish I had one here to do a picture run-through. May take mine out at some point next week.....maybe.

Jase..
Wink

_________________
2001 Avus Silver RS4.
2004 A4 Avant 1.8T quattro Sport LE..

1995 S2 Coupe - sold
1995 A6 Avant TDi - sold
1993 80 TDi - sold
1990 90 2.3 auto - scrapped
1989 Coupe 2.3e - sold
1990 cq20v - sold
1990 80 2.8 quattro - sold 
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PostPosted: Sun Nov 23, 2008 4:20 pm Reply with quote Back to top

Im trying to do this for my uncle at the mo, what exactly does that bulb in the tube do? From what i can see it does nothing!?

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PostPosted: Sun Nov 23, 2008 4:41 pm Reply with quote Back to top

It lights up the green spot to tell you the difflock is on Wink

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2004 A4 Avant 1.8T quattro Sport LE..

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1995 A6 Avant TDi - sold
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PostPosted: Sun Nov 23, 2008 4:47 pm Reply with quote Back to top

but there is a bulb behind that in a tube that does nothing, hang on and i'll take some pics

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PostPosted: Sun Nov 23, 2008 5:03 pm Reply with quote Back to top



The bulb with green arrow lights up the car picture, the blue arrow lights up the green dot on the car pic bu what does the red arrow do??

Jim

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PostPosted: Sun Nov 23, 2008 5:05 pm Reply with quote Back to top

That's the earlier big buttoned bugger, it lights up the button itself.

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2004 A4 Avant 1.8T quattro Sport LE..

1995 S2 Coupe - sold
1995 A6 Avant TDi - sold
1993 80 TDi - sold
1990 90 2.3 auto - scrapped
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1990 80 2.8 quattro - sold 
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PostPosted: Sun Nov 23, 2008 5:14 pm Reply with quote Back to top

Ahh but the one on my uncles s2 has a seperate button that is lit up by its self

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PostPosted: Sun Nov 23, 2008 5:19 pm Reply with quote Back to top

bikerjim wrote:
Ahh but the one on my uncles s2 has a seperate button that is lit up by its self


I don't know, I can't tell from just one picture.
I've never changed bulbs in the huge big buttoned difflock switch.

Just the later small buttoned switch. That has three bulbs, two for illuminating the image of the drivetrain and one for the green light showing the difflock is on. It doesn't have it's button illuminated.

_________________
2001 Avus Silver RS4.
2004 A4 Avant 1.8T quattro Sport LE..

1995 S2 Coupe - sold
1995 A6 Avant TDi - sold
1993 80 TDi - sold
1990 90 2.3 auto - scrapped
1989 Coupe 2.3e - sold
1990 cq20v - sold
1990 80 2.8 quattro - sold 
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PostPosted: Sun Nov 23, 2008 5:54 pm Reply with quote Back to top

Ignore that above, the later small buttoned switch does have the button illuminated.
Three bulbs, one for drivetrain image, one for green difflock "on" indicator and one for the word "diff" on the button.
It's well over two years since I had one to bits.

_________________
2001 Avus Silver RS4.
2004 A4 Avant 1.8T quattro Sport LE..

1995 S2 Coupe - sold
1995 A6 Avant TDi - sold
1993 80 TDi - sold
1990 90 2.3 auto - scrapped
1989 Coupe 2.3e - sold
1990 cq20v - sold
1990 80 2.8 quattro - sold 
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PostPosted: Sun Nov 23, 2008 6:02 pm Reply with quote Back to top

this is funny,2 backlight bulbs(shows the axles)1 for the green dot and a separate one or 3 for the diff switch(i`ve got it apart in front of me) Wink

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Last edited by taylormade on Sun Nov 23, 2008 10:40 pm; edited 1 time in total 
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PostPosted: Sun Nov 23, 2008 6:10 pm Reply with quote Back to top

jas11n wrote:
unless I get another to do a run-through on, or take mine out just to replace bulbs that haven't gone, then we'll have to wait for that.



I see I'm going to have to go and pull my perfectly good one out tomorrow Rolling Eyes Laughing
I knew I should have locked this thread until everything was done Twisted Evil

_________________
2001 Avus Silver RS4.
2004 A4 Avant 1.8T quattro Sport LE..

1995 S2 Coupe - sold
1995 A6 Avant TDi - sold
1993 80 TDi - sold
1990 90 2.3 auto - scrapped
1989 Coupe 2.3e - sold
1990 cq20v - sold
1990 80 2.8 quattro - sold 
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PostPosted: Sun Nov 23, 2008 8:03 pm Reply with quote Back to top

Quote:
I see I'm going to have to go and pull my perfectly good one out tomorrow
I knew I should have locked this thread until everything was done



oops,i only posted here because i seen your sticky.just pull my posts and all will be well. Smile

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PostPosted: Sun Nov 23, 2008 9:05 pm Reply with quote Back to top

taylormade wrote:
Quote:
I see I'm going to have to go and pull my perfectly good one out tomorrow
I knew I should have locked this thread until everything was done



oops,i only posted here because i seen your sticky.just pull my posts and all will be well. Smile


I'm joking matey Very Happy Wink

_________________
2001 Avus Silver RS4.
2004 A4 Avant 1.8T quattro Sport LE..

1995 S2 Coupe - sold
1995 A6 Avant TDi - sold
1993 80 TDi - sold
1990 90 2.3 auto - scrapped
1989 Coupe 2.3e - sold
1990 cq20v - sold
1990 80 2.8 quattro - sold 
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PostPosted: Sun Nov 23, 2008 10:42 pm Reply with quote Back to top

lol, pull mine aswell jase if you like, i can start a new one. My uncles s2 is a N 95 by the way. Its bugging me now, i was there today, should of taken pics. From what i can see with having the both the top and bottom part and pulling them apart a little that bulb in the tube does nothing. I'll see if trevor can take some pics for me 2mora.

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PostPosted: Sun Nov 23, 2008 10:56 pm Reply with quote Back to top

We'll tidy the thread up later, as someone said in another thread today, no discussion, no forum Wink

It's at least two years ago since I had one to bits. I replaced them in my cq20v years ago, even though I can hardly remember it (big button switch) and then in my S2 (small button) when I bought it (2004). I then replaced those in Paulgo's switch and a couple of S2forum users switches a couple of years back.
Only the other day someone stated that the last ones had LED's, so that's at least three versions so far.
Rory is probably right with the four bulbs, it's just so long ago.

I'll pull mine tomorrow and open it up. I'm 100% sure all illuminate though.
Your uncles should be a small switch version, but your picture above looks very different.
It'll sort itself out Wink One thing though, the bulbs CAN be replaced very easily.

Here's what mine looks like lit up normally and with the difflock on (small button switch)





Jase..

_________________
2001 Avus Silver RS4.
2004 A4 Avant 1.8T quattro Sport LE..

1995 S2 Coupe - sold
1995 A6 Avant TDi - sold
1993 80 TDi - sold
1990 90 2.3 auto - scrapped
1989 Coupe 2.3e - sold
1990 cq20v - sold
1990 80 2.8 quattro - sold 
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PostPosted: Mon Nov 24, 2008 11:45 am Reply with quote Back to top

Quote:
TOO AVOID CONFUSION, this is the later small button'ed switch I'm referring to here.




Green arrow = drivetrain illumination
Red arrow = drivetrain illumination
Blue arrow = green difflock activation illumination.

Apply a 12v source to the tracks on the rear for the green arrowed bulb (even though they are bulbs, they need earth one way as they run through the resistors) Once you do that, you should see the red arrowed bulb illuminate at the same time. If it doesn't, it's shot. A first glance, it looks like when it's fitted together, the red arrowed bulb just shines down into a blank space, but look closely, you'll see it illuminate the drivetrain image too Wink

There's actually 5 (five) points of illumination in the whole unit, two inside the actual push button switch itself (a bulb and a red LED)

I'll post up the entire run-through once I've edited the pictures.
It was a good exercise, I found the bulb inside the actual push button switch on mine was dead, a small triangle should illuminate behind the red "Diff" text when the difflock is on.
I've not noticed it before as I can count on one finger the times I've used the difflock.

Jase..
Wink

_________________
2001 Avus Silver RS4.
2004 A4 Avant 1.8T quattro Sport LE..

1995 S2 Coupe - sold
1995 A6 Avant TDi - sold
1993 80 TDi - sold
1990 90 2.3 auto - scrapped
1989 Coupe 2.3e - sold
1990 cq20v - sold
1990 80 2.8 quattro - sold 
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PostPosted: Thu Nov 27, 2008 3:18 am Reply with quote Back to top

Right, finally got a bit of time to write this up. This is for the smaller buttoned switch.

Ever heard of the saying "If it ain't broke, don't fix it?"
I need to have that in mind next time. This exercise the other day cost me a diiflock circuit board. The things I do in the name of Audiness Laughing There was nothing wrong with my switch illumination, but after I finished there was.

First up, look at this picture below, look at it a good few times, even open it in another window, whatever. Just take note.

You are looking at the way the plastic block is screwed to the main body of the difflock unit.
When coming to reassemble your switch after you've replaced which ever blown bulbs, you CAN fit it 180° the other way. If you do this, and reconnect it to your wiring plug in the car, IT WILL blow the small black three legged transistor (I assume it's a transistor) and the circuit will be junk.

The block must be refitted exactly as shown below



Looked at the above picture??? Look again.

Right; First up, as said, I haven't got a run-through of the earlier large buttoned switch, I haven't got one to do a run-through on it.
Though the earlier versions drivetrain image is the same size, the push switch is a lot larger and is the same size as the switches on the dash.
If you want a later one, you'll need the rear centre console too, the oblong hole it fits in is a lot larger on the earlier consoles. The multiplugs on the rear of the earlier switch are different too.

There's two ways to remove it, it's up to you which way you do it. If you pick my way and damage it, don't blame me. Remove the rear centre console if you must.

I use a blade and carefully slot it under the front, then prise the front up;




Then do the same at the rear




Pull off the two multiplugs then remove from the car;



Remove the two screws and put the block to one side;



Now you can just lift up the circuit board;



Flip it over to reveal the bulbs. The yellow arrows point to the two bulbs that illuminate the drivetrain image, the green arrow points to the bulb that illuminates the green spot seen in the rear axle of the image when the difflock is on.



You can use one of two types of bulb for this. As you can see in mine, I used small wired bulbs from Maplins, code >>> PG77J
If you want the image to be slightly dimmer, the small bulbs used earlier in this thread for the mirror control switch are just as good.

Now, normally the text "DIFF" is illuminated at all times the car's ignition is on (the drivetrain image will only light with ignition AND lights).
If your text isn't illuminated, the red LED inside the push button will have gone. There's also a bulb inside that illuminates a yellow triangle behind the text. That will only illuminate when the difflock is on.

To remove the push button unit from the main body, get your blade and insert it down the side, gently lever the blade against it while pushing from the other side and it will come out from above;



Once it's out of the main body, again use your blade/tool to carefully lever up the main body from the tangs on the internal part, there two either side;




The LED's used for the window switch illumination are again perfect for the replacing the LED in the push switch should you need to. You need to know which is the earth side of the LED (short leg of the LED), I've arrowed it below. If you are replacing this, then you'll need to junk the resistor in there, use a piece of thin wire to follow the old resistors route around the switch, or route the longer leg of the LED round the back



Here's what it should look like;



And when the difflock is on;



I'm sorry I've not shown any soldering of new bulbs, but as I said back at the beginning, my switch "was" ok as I'd done it way back when I bought the car years ago.
Big thanks to Sal for the replacement switch Very Happy

[If someone has a spare earlier switch, or maybe a switch with duff illumination that they want fixing, let me know and I'll do a run-through for that too]

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2001 Avus Silver RS4.
2004 A4 Avant 1.8T quattro Sport LE..

1995 S2 Coupe - sold
1995 A6 Avant TDi - sold
1993 80 TDi - sold
1990 90 2.3 auto - scrapped
1989 Coupe 2.3e - sold
1990 cq20v - sold
1990 80 2.8 quattro - sold 
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bikerjim
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Joined: Jan 29, 2008
Posts: 580
Location: Harrogate N Yorks

PostPosted: Thu Nov 27, 2008 9:27 pm Reply with quote Back to top

Thanks for that jase, i still dont really see the point in that second bulb but anyway, guess thats audis over engineering Cool

Just need to get some bulbs now Very Happy

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jas11n
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Joined: Nov 21, 2003
Posts: 14191
Location: Durham, United Kingdom

PostPosted: Fri Nov 28, 2008 12:23 am Reply with quote Back to top

bikerjim wrote:
Thanks for that jase, i still dont really see the point in that second bulb but anyway, guess thats audis over engineering Cool

Just need to get some bulbs now Very Happy


If one is out, that end is dull compared to the other. I suppose they could have had one in the middle, but then it would have had to have been brighter, if it's brighter it's hotter, not something you want really Wink

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2001 Avus Silver RS4.
2004 A4 Avant 1.8T quattro Sport LE..

1995 S2 Coupe - sold
1995 A6 Avant TDi - sold
1993 80 TDi - sold
1990 90 2.3 auto - scrapped
1989 Coupe 2.3e - sold
1990 cq20v - sold
1990 80 2.8 quattro - sold 
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jas11n
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Joined: Nov 21, 2003
Posts: 14191
Location: Durham, United Kingdom

PostPosted: Fri Nov 28, 2008 11:43 pm Reply with quote Back to top

All these components in just one switch Shocked Laughing


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2001 Avus Silver RS4.
2004 A4 Avant 1.8T quattro Sport LE..

1995 S2 Coupe - sold
1995 A6 Avant TDi - sold
1993 80 TDi - sold
1990 90 2.3 auto - scrapped
1989 Coupe 2.3e - sold
1990 cq20v - sold
1990 80 2.8 quattro - sold 
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evilgoat
Needs to get out more



Joined: Jun 27, 2007
Posts: 126
Location: Southampton

PostPosted: Sat Nov 29, 2008 1:05 pm Reply with quote Back to top

Hmm, lm339 in the middle, fader control?

BTW the difflock light, if you feel brave the 'lock' buld, or any of them, can be replaced with a LED of your choice and 330 ohm resistor, in my case it went blue Smile Watch the polarity though.

I have a spare difflock board kicking about if you need it jas11n?

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jas11n
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Location: Durham, United Kingdom

PostPosted: Sat Nov 29, 2008 1:54 pm Reply with quote Back to top

It's a later type heated seat switch Smile

There's the early short switch, same approximate size as the headlamp level switch. This used two relays on the aux relay carrier, one relay for each front seat.

Later they dumped the separate relays and you have what you see above. Two versions of the above, "ever" so slightly different in the illumination department, one used a red bulb, other used a clear LED that illuminated red. Slightly different clear plastic interior for refracting the light.

Of the two larger versions, the switch with the red bulb is easy to do, the version with the LED, is a LOT more complicated, you have to practically dismantle the whole thing.

Busy compiling a post. I haven't an earlier "short" seat heater switch......yet!!

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2001 Avus Silver RS4.
2004 A4 Avant 1.8T quattro Sport LE..

1995 S2 Coupe - sold
1995 A6 Avant TDi - sold
1993 80 TDi - sold
1990 90 2.3 auto - scrapped
1989 Coupe 2.3e - sold
1990 cq20v - sold
1990 80 2.8 quattro - sold 
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taylormade
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Joined: Nov 05, 2006
Posts: 302
Location: inverness

PostPosted: Sat Nov 29, 2008 10:20 pm Reply with quote Back to top

Quote:
You are looking at the way the plastic block is screwed to the main body of the difflock unit.
When coming to reassemble your switch after you've replaced which ever blown bulbs, you CAN fit it 180° the other way. If you do this, and reconnect it to your wiring plug in the car, IT WILL blow the small black three legged transistor (I assume it's a transistor) and the circuit will be junk.



another good write up jase just wish i had seen this bit before i did mine.i actually blew mine first but being a novice at soldering i didn`t know what went wrong.i managed to get another one so well see if it works when delivered.

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jas11n
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PostPosted: Sat Nov 29, 2008 11:08 pm Reply with quote Back to top

Ah bugger, easy mistake to make Rory. After doing 4 or 5 of these over the years, I guess I've been lucky as I've not taken much notice.

I was right, the three legged little blighter is a transistor. BC547B (Epitaxial Silicon Transistor).

I've managed to source some. Will have a go at repairing my borked one, for no other reason than to see if I can Laughing



Can you see I'm running out of things to poke and prod??

Jase..
Very Happy

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2001 Avus Silver RS4.
2004 A4 Avant 1.8T quattro Sport LE..

1995 S2 Coupe - sold
1995 A6 Avant TDi - sold
1993 80 TDi - sold
1990 90 2.3 auto - scrapped
1989 Coupe 2.3e - sold
1990 cq20v - sold
1990 80 2.8 quattro - sold 
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jas11n
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Joined: Nov 21, 2003
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Location: Durham, United Kingdom

PostPosted: Sun Nov 30, 2008 1:45 am Reply with quote Back to top

As mentioned above, there are three versions of the seat heater switches.

I haven't presently got an earlier shorter one, though I should have two of them in a week or so. You can see the difference between the size of them below. One shorter and two versions of the later longer ones.
Shorter = 5 pin
Longer = 6 pin
They do not swap with each other.




I have two of the later big versions (which are probably the very last of them).
The difference with the two versions of the larger switches is the source of the illumination, differences with the circuit board and a slight difference of the clear plastic light refractor inside.

If you have this version below, easy job to replace the bulb, with either a new red bulb (Maplins code >>> PG78K), or a red LED (CJ70M), Refer to the control drawing further down the thread for the two solder points and the polarity (Led shorter leg = negative) Use a matchstick or similar superglued to the top of the bulb and withdraw through the hole in the top of the light tube while de-soldering.



If you have this below, then it's get complicated. There is no hole in the top of the clear light refractor, this version uses a clear 3mm LED that shines red.
This means you have to do some major de-soldering. You will need a de-solder pump for this and very fine tipped soldering iron.



Ok, how to open them up.

Remove the front cover as usual, get your blade and slot it carefully down the side of the rear of the switch. The inner unit is again clipped behind a couple of tangs on the inside of the outer case. The switch withdraws from the front




You are going to have to remove that massive copper heatsink. Not only is is soldered to the board in three places round it's edge, but also on three places on the centre of the board itself. Use the drawing below. You need to de-solder all the red arrowed points



And removed



You have to remove it to be able to remove the clear light refractor. Part of the light refractor is a switch of sorts, that has to be de-soldered to be able to finally get to the OEM LED. The points needed to be de-soldered here are the blue arrowed ones




Again with this switch, there is a tiny part you need to watch out for. A rounded tipped pin sits inside the clear plastic with a spring behind it. If you aren't careful here, that pin will either fire off and you'll never see it again, or it'll have your eye out. It's job is to sit in the position notches on the upper inner rim of the rotary knob




Now you can finally get to the LED. Refer back to the drawing above to the de-solder points. If replacing with a red bulb, it doesn't matter which way round you solder it, but if you replace with another LED, the shorter leg needs to go to the earth side shown above



I used a CJ70M 3mm LED for this




Once done, start to reassemble it. Due to the small components on the board, best be quick with the de-soldering and re-soldering. Heat kills small components




Testing it is illuminating ok,



Slotted back in the outer casing



Done, with the usual out of focus dark shot at the end Embarassed



_________________
2001 Avus Silver RS4.
2004 A4 Avant 1.8T quattro Sport LE..

1995 S2 Coupe - sold
1995 A6 Avant TDi - sold
1993 80 TDi - sold
1990 90 2.3 auto - scrapped
1989 Coupe 2.3e - sold
1990 cq20v - sold
1990 80 2.8 quattro - sold 
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evilgoat
Needs to get out more



Joined: Jun 27, 2007
Posts: 126
Location: Southampton

PostPosted: Sun Nov 30, 2008 12:39 pm Reply with quote Back to top

Not sure I like the pot they used Sad Seen them go bad quite a lot used this way, bad Audi. Replacement part could be had from RS, CPC, Farnell, Maplin or Rapid for a few pence, might be some snese in changing it while its apart.

Oh, Blue Difflock...


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