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Had a lucky find in a breakers yard on an old A6 of a complete outside temperature gauge. Bought the lot for £5.
Looks like an easy install based on the procedure in the sticky.Three of the wires are on the autobox gear indicator. the fourth is the temp sensor and the fifth is a speed signal.
Question is what on earth does a temperature gauge need a speed signal for?
Mikes2 Site Moderator
Joined: Jan 31, 2003
Posts: 8273
Location: Polmont
Posted:
Sat May 15, 2010 11:06 am
So that the temperature is correct when the car is travelling at speed
_________________ Mike
1988 quattro - the 1st UK MB
1991 90 sport quattro 20v
Joined: Jan 20, 2003
Posts: 13250
Location: N.E. Scotland
Posted:
Sat May 15, 2010 1:33 pm
Chill factor?
_________________ 1995 80 quattro (work in progress)
1994 80 "Project Titan" - Now deceased
1993 S2 Coupe - Sold
1989 CQ20V - Sold
1986 Coupe GT - Deceased
1985 Coupe GT - Deceased
CCV6 Bandwidth Buster
Joined: Feb 22, 2010
Posts: 589
Location: Glasgow
Posted:
Sat May 15, 2010 1:51 pm
Temperature is temperature, it does not change at speed.
What increases with speed is wind chill or the rate at which heat is lost, but 5deg is 5 deg... it just feels like 2deg when you are doing 50mph as you are losing heat faster.
The gauge is not a wind chill meter. Must be some other reason for it.
Mikes2 Site Moderator
Joined: Jan 31, 2003
Posts: 8273
Location: Polmont
Posted:
Sat May 15, 2010 10:11 pm
yes it does change.
It's ambient air temperature - that's what it measures and it sits right at the front of the car in the air flow.
Are you trying to tell me that the sensor will get the same reading at 0 mph as it does at 120mph
_________________ Mike
1988 quattro - the 1st UK MB
1991 90 sport quattro 20v
Yes. Air temperature at 120mph is the same as at 5mph. Hang a mercury thermometer out the window and it will not change with speed (unless its been heated by direct sunlight when stationary).
The sensor is not a hot wire that is cooled by air flow. Its simply reacts to a change in temperature by changing resistance.
My guess is to prevent false readings in traffic. The sensor mount is in front of the radiator. When the engine is hot and the car is stationary the radiated heat from the radiator gives a false reading. The display seems to stop taking data for a time lag but as soon as the car moves it starts taking data again. Still to wire the speed sensor but not wiring produces a 60 second time lag between updates. Will check and confirm this and let you know.
cq20v Site ADMIN
Joined: Jan 20, 2003
Posts: 13250
Location: N.E. Scotland
Posted:
Sun May 16, 2010 12:54 pm
It's not that as my S2 one used to rise when stationary.
The air may be the same temperature at 0mph and 120 mph but increase in speed will have a cooling effect - if not why bother with cooling fans?
It may not be a hot wire but it is still a solid state "thermometer" and so will be subjected to a cooling effect with speed.
_________________ 1995 80 quattro (work in progress)
1994 80 "Project Titan" - Now deceased
1993 S2 Coupe - Sold
1989 CQ20V - Sold
1986 Coupe GT - Deceased
1985 Coupe GT - Deceased
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