Quote Originally Posted by NZDubNurd View Post
I'm not sure if your PTC is the same as in the MK5s... but mine is in my MK5 based Touran, and it only remains functional until the engine hits 75C. There are other factors, like the requested heat has to be over a certain % of the available heat, minimum engine speed (like 600 RPM or something). There is no battery energy management system though, like you have.

A battery may help... as Uwe said, it's seeing some low voltages. If the engine is over 75C though, I'd have assumed it wasn't running the PTC though.

You can log the coolant temp with VCDS, and it will report the measured temperature, instead of the gauge reading. (On my Tourans Climatronic HVAC controller, I can access the secret menu and watch it while I drive... proper nerd style!)
Ok, thanks Allan, I'll have a go at checking the coolant temp directly and see what transpires. I've ordered a battery tester to load and check the battery before I replace it. My wife tells me that the car is driving fine and the heater is OK so will do a bit more investigation over the next couple of weeks. I'f I fix it I'll report back here.

Many thanks all for the advise.