2004 A6 C5 Avant 1.9TDI water and oil temperature gauges not reading

A7DUO

New Member
Joined
Feb 22, 2025
Messages
7
Reaction score
0
Points
1
Location
ct66jp
Since I bought my car a year ago the oil and water temp. has only moved from 60degC to 65degC on both

Serviced recently and in my preferred independent shop the tech used OBD port to test the gague cluster and both temp needles work/responded to a test

So I changed the oil level sender, coolant temp sensor (initially with a cheap pattern part), I also put a new decent brand thermostat in the car

When I got the car back the needle didn't even move from 60degC at the bottom of the scale on a 20 mile drive.

So I bought correct OEM VAG coolant temp. sensor. Ran the car for 10mins. on the drive and even with this fitted the needle didn't move on either oil or water.
I'll take it out for a longer drive tomorrow, but I don't hold out much hope.

It seems I've gone from a sensor that only registered a 5 degree difference when the car was upto temperature to a costly OEM new one that is no better at fixing the problem then a cheap pattern part (neither of which work). I am thinking now it could be a wiring fault?

Can anyone think of anything else to check to get these temp. gagues working again?
Also anyone know if the car will run correctly if these guages are not displaying correctly (I've got a feeling I should get some better MPG if they work as I'm suspect the ECU is always thinking the car is cold - even on a long motorway drive)
 
Okay - Water temperature is now reading with the new OEM VAG sensor fitted.

Oil temperature still not working - so anyone know where the C5 A6 TDI gets its oil temp. reading from? as that is all I have outstanding to fix on it

1768749184204
 
Last edited:
Just replied to similar query on B5 forum on 2000 1.8. Is temperature and oil level sensor in integrated unit on sump?
 
  • Like
Reactions: A7DUO
thanks, yes I'm not sure. I did replace the sump oil level sensor (with a cheap pattern part) but I've not seen the guauge respond just yet (and its only a 3-wire connector on that, so I'm not sure if it has an oil temperature sensor in it) or even if I have a wiring fault to that. I changed everything in this photo to rule out these senders and thermostat at fault
1768816977190