Audi TT temp warning strange behaviour ! Any ideas ?
Discussion
Audi TT 1.8 225 110k
Intermittent (every other day or so) temp needle going in to Red zone and high temp warning symbol.
Checked fans via radiator switch jumper, both work Hi and Lo speed.
Changed temp sensor, radiator fan switch and Thermostat all with genuine VAG parts.
Water pump replaced about 30k miles ago.
Cleaned sensor wires in coolant header tank.
Not loosing any coolant, drives perfectly.
When AC on both fans operate at Low speed, which I believe is correct.
Since monitoring 49c temp went to 110C today but, temp needle did not go in to Red nor did warning symbol come on !! this temp of 110C was at a normal driving conditions eg no traffic or high revs.
Will keep monitoring 49C. Any ideas ?
Cheers
Mark T
Intermittent (every other day or so) temp needle going in to Red zone and high temp warning symbol.
Checked fans via radiator switch jumper, both work Hi and Lo speed.
Changed temp sensor, radiator fan switch and Thermostat all with genuine VAG parts.
Water pump replaced about 30k miles ago.
Cleaned sensor wires in coolant header tank.
Not loosing any coolant, drives perfectly.
When AC on both fans operate at Low speed, which I believe is correct.
Since monitoring 49c temp went to 110C today but, temp needle did not go in to Red nor did warning symbol come on !! this temp of 110C was at a normal driving conditions eg no traffic or high revs.
Will keep monitoring 49C. Any ideas ?
Cheers
Mark T
If the fans aren't on when the dash gauge is reading 110 degrees, then the gauge is lying, given everything you've replaced thus far.
That is what Cuprabob means regarding faulty instrument binnacles, it's a VERY well document TT problem. Many were replaced under warranty in the early TT years.
If it really is 110 degrees and still no fans, it's probably the fan control module, pic & part no. here - https://www.ebay.co.uk/p/AUDI-TT-Mk1-1998-2006-Rad...
That is what Cuprabob means regarding faulty instrument binnacles, it's a VERY well document TT problem. Many were replaced under warranty in the early TT years.
If it really is 110 degrees and still no fans, it's probably the fan control module, pic & part no. here - https://www.ebay.co.uk/p/AUDI-TT-Mk1-1998-2006-Rad...
Many thanks to both, for clarity the physical gauge reads 100C when at normal 85-95C and this is just the one of the well known instrument faults, the 110C was show on the 49c output, so the same question why would the physical gauge not jump the the equevelent of 110C ? Cheers Mark T.
Because that is how the analogue gauge is calibrated.
As Bob said, the analogue gauge is deliberately set to be 'in the middle' 90% of the time because that is what average joe is comfortable with.
My MK4 R32 (same fan setup essentially) was the same, but so long as the fans came on when they were supposed to, I didn't care.
90 on the gauge was 83 in reality, and 100 on the gauge was 110+ actual. It only every went far right at 120+ degrees actual.
As Bob said, the analogue gauge is deliberately set to be 'in the middle' 90% of the time because that is what average joe is comfortable with.
My MK4 R32 (same fan setup essentially) was the same, but so long as the fans came on when they were supposed to, I didn't care.
90 on the gauge was 83 in reality, and 100 on the gauge was 110+ actual. It only every went far right at 120+ degrees actual.
Think we are crosswired
I'll try again.. If the physical gauge temp is clamped at 90C when the actual/49c temp is between 85-105C (this common practice on most modern cars) why would the physical gauge not jump to 110 when the actual temp/49c goes to 110, I can only think that the clamp range must be greater than 105C (as previously advised) or 110C e.g. 111 or 115C.......
If the fan control module was faulty, why would it work when I link the radiator fan switch between hi and lo ? Or is there some other input to the control module ?
Mark T
I'll try again.. If the physical gauge temp is clamped at 90C when the actual/49c temp is between 85-105C (this common practice on most modern cars) why would the physical gauge not jump to 110 when the actual temp/49c goes to 110, I can only think that the clamp range must be greater than 105C (as previously advised) or 110C e.g. 111 or 115C.......
If the fan control module was faulty, why would it work when I link the radiator fan switch between hi and lo ? Or is there some other input to the control module ?
Mark T
We are not cross-wired, you are just not understanding what we are saying. I've already said exactly what you said in your 3rd sentence - it doesn't move to the right until 110c is exceeded. You don't seem to be able to detach yourself from '49c' and the analogue gauge. They are completely different entities.
The fan controller has an input from the engine ECU, as well as the 3 pin radiator switch. It's more sophisticated than it first seems.
The fan controller has an input from the engine ECU, as well as the 3 pin radiator switch. It's more sophisticated than it first seems.
Fixanything said:
Update: After a week of operating fine today the 49c temp went to 120C the temp gauge went to ~120C and the over temp warning lamp came on, fans were operating. Stopped for a few minutes temp perfectly ok finished 15min trip no problems. ?
Have now changed the Fan Control Module, but Same again today, drives perfectly in all sorts of conditions for about 30mins and then quite randomly 49C and Temp gauge go to 121C (max I have seen) high speed fans come on and temp drops to a rock solid 88C and stayed like this for the remainder of journey about 30mins. I'm running out of ideas, any help much appreciated. Airlock, wiring, !?
Cuprabob and superchargedvr6 thanks for your help.
Regards
Mark T
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