Strange temperature gauge behaviour

[tobee1k]

I have just had my A2 in the garage (replacing drop links again - thank you Scottish roads!) and they have been unable to diagnose this problem.

For as long as I've had the car (about a year), the temperature gauge basically doesn't work. When I say basically, I mean 90% of the time, it does nothing, just sits on cold. Sometimes it will slowly come up to temperature, sit at 90 for a minute or two and then gradually drop back down to cold. Mostly it does nothing though.

The garage plugged in and no faults were recorded, they said that the sensor was working properly.

I'm at a bit of a loss, everything else seems to work fine, coolant level is correct, the engine doesn't overheat, the fan kicks in as it should, heater in the car works properly and consistently.

Any thoughts?

 

[Robthebank]

It’s common for the thermostat and or temperature sensor to be at fault (I had both). Although a garage should know that. It’s rarely anything more sinister.

 

[PlasticMac]

Hi, have you checked the temperature on the A/C diagnostics:

This is quick and easy, and will point you in the right direction.

You can check the actual gauge operation with VCDS:

Mac.

 

[tobee1k]

Unfortunately I don't have the digital climate control - very painful in the summer!

I'll look at the gauge operation though.

Thanks both

 

[cheechy]

It’s common for the thermostat and or temperature sensor to be at fault (I had both). Although a garage should know that. It’s rarely anything more sinister.

Yup agreed - just change both (green sensor and thermostat). If its still not getting up to temp then something else is going on.

 

[AndyP]

I was mucking about with an old sensor at the weekend. It turns out there there are two sensors in the unit, as opposed to one with two outputs. When cold the resistance is about 1.5Kohm and when hot (in near boiling water) it drops to about 300ohms. One of the sensors in this one only dropped to about 500ohms, so that probably explains why either the ECU is confused and thinks the engine is not warmed up, or the gauge displays low.

 

[Proghound]

I don't think the thermostat is faulty - the car is reported as getting proper and consistent heat in the cabin. The temp sensor is goosed though. It has two sides, one sends the temp signal to the ECU, the other to the gauge. Again it sounds like the ECU side is working fine (fan comes on) but the gauge side is intermittent.

 

[tobee1k]

I was mucking about with an old sensor at the weekend. It turns out there there are two sensors in the unit, as opposed to one with two outputs. When cold the resistance is about 1.5Kohm and when hot (in near boiling water) it drops to about 300ohms. One of the sensors in this one only dropped to about 500ohms, so that probably explains why either the ECU is confused and thinks the engine is not warmed up, or the gauge displays low.

OK thanks, that sounds like its worth investigating.

 

[tobee1k]

I don't think the thermostat is faulty - the car is reported as getting proper and consistent heat in the cabin. The temp sensor is goosed though. It has two sides, one sends the temp signal to the ECU, the other to the gauge. Again it sounds like the ECU side is working fine (fan comes on) but the gauge side is intermittent.

Cheers yes, this sounds likely

 

[audifan]

Swap the temp sensor, buy a spare clip for it, tie string around the old clip to remove it. Make sure the o ring comes out with the sensor and a gush of coolant. New o ring on new sensor and orientate the plug the same way as the old sensor came out. Tie string onto the new clip - if you don't and drop it you will regret not doing so. clip in plug on top up coolant, run up to temp checking for leaks, and watching the gauge. Let cool and top up again if required. Only use the correct coolant G12, G12+, G12++ or G13 and do not mix with any other type of coolant.
Forget about the nonsense about the hidden menu in the climate . IT DOES NOT EXIST ON THE A2. also irrelevant for non climate cars.

 

[Imola Yellow]

I had very similar symptoms - mostly nothing, and occasionally it would get up to 70 degrees before dropping again. The first thing was a new sensor at New Year, which improved things considerably - in spite of previously having it replaced but still not work.
This led to detecting that the thermostat was stuck, causing the engine to stay cool, so I had that replaced.
Much better! But then I realised that the fan wasn't working, when it overheated in a motorway queue.
So new fan, and now it gets up to 90 degrees and stays there.
Plenty to check!

 

[PlasticMac]

Forget about the nonsense about the hidden menu in the climate . IT DOES NOT EXIST ON THE A2. also irrelevant for non climate cars.

Teach me to believe what I see on the internet! Does work on the TT though ... not much help on an A2 of course.
Mac.

 

[phipsey]

Hi, have you checked the temperature on the A/C diagnostics:

This is quick and easy, and will point you in the right direction.

You can check the actual gauge operation with VCDS:

Mac.

Is it possible to activate the gauge-sweep in our A2s?? Would be a cool gimmick…