Hi guys hopefully someone can help with this,

My heater starts off working then increases to very hot before blowing completely cold.

Could this be the thermostat?

If it's the thermostat then what's the temp gauge showing while this is happening? I'd suggest an air lock but the fabia isn't exactly rebound for them.

Thanks Avalon

The temp gauge on the dials is spot on. Could the heater panel itself be faulty?

If it is an air lock how would this be fixed?

It is commonly the sensor built into the heater control panel from what I have read. Mine is dodgy and regardless of the dial position only produces fire! It is sometimes ok for a few days once clearing the codes with vcds then its back to furnace mode. I keep putting off buying another unit as part of me always thinks a 2nd hand one may have the same issue.

I do have a spare unit I could try. Just a pain in the ass to change lol

Do you know where the sensor is?

Do you know where the sensor is?

True about it being a pain. And not sure of sensor location but i had though that a soldering god like yourself may be able to change it if the sensor part was available. if you find out would be good to know.

I'll have a look on the spare to see if I can find the sensor

If it's the thermostat then what's the temp gauge showing while this is happening? I'd suggest an air lock but the fabia isn't exactly rebound for them.

I did have a majority of the coolant lines replaced with braided lines. Could this have caused an air lock?

And this is what the heater panel looks like when its removed and taken apart

I'd guess the sensor is on the bottom of the second pic

I did have a majority of the coolant lines replaced with braided lines. Could this have caused an air lock?

And this is what the heater panel looks like when its removed and taken apart

I'd guess the sensor is on the bottom of the second pic

That does look rather more complicated that expected! I'm guessing it would be near on impossible to find the right part to replace and actually make it work. Presuming that is the problem :/