2001 A3 1.6 sport petrol 8L. 140K miles. FWD.

My son has had overheating problems so I tried to help. He had blown the head so i had a fair size job on my hands. I got an overheat straight away and went chasing an airlock but to no avail. I took out the thermostat and wired it to a battery and hot water tested it and it opened fine.

I don't have good voltage to the thermostat feed. There is something there but it flicks on and off continuously but never shows more than 0.5V. I'm pretty sure it was showing 14V earlier in my investigations.

Does anyone know what voltage I should see? And where in the loom do these wires go? I am thinking a break in a wire or bad terminal but where to look?

As a stop gap, I have compromissed the thermostat to stop it closing and the car stays cools as expected.

 

what do you mean you hooked up a battery to the thermostat? the thermostat is mechanical and would open in hot water if it was functioning correctly.

just replace thermostat if this is whats causing the issue. from what you said about keeping the thermostat from closing and the car doesn't overheat anymore definitely points to a bad thermostat.

if your replacing thermostat, might as well replace the coolant temp sensor whie your at it and do a coolant flush as well.

 

This car has an electronic thermostat. Looks like this:



I plan to remove the thermostat and modify the housing to accept a mechanical stat.

 

the thermostat on the engine the OP is referring to uses a electronic activated thermostat assembly.

i believe it looks like this

I am not familiar with those engines overseas but if its anything like the BMW which im very familiar with, you will not get a real voltage reading as the computer sending signals to the thermostat at certain temps and throttle position

 

Stat is electric. Already done the coolant sensor and coolant along with head gasket, cam belt, water pump and new plugs. Coolant sensor was faulty and not reading at all. This was causing overfuelling and hot start issues. At least it starts well now.

 

My bodge/solution.
Do you think I need to wire a 15ohm resistor across the feed wire to replicate the thermostats resistance?