The new item is genuine VAG from TPS and granted the old unit could well go open circuit when hot.
Sean,
Not quite sure where you are getting your attitude from.
My basic tests found a split breather pipe, a knackered thermostat and a corroded rivet on the secondary air pump (which I forgot to write down). Admittedly I did not check the heater resistance before replacing the unit, if it had a connector under the bonnet I would have, but I have to use the ramp of a friend next door. I do not like to impose on his time too much, so I did not want to put it on his ramp twice.
You say it is a basic system to check but VCDS shows the heater status switching on and off continuously so it is not just fed from the fuel pump relay then. It must therefore be driven by the PCM and testing will be much simpler with the pinout data.
The fault code cleared and did not return on roadtest. I only found out that there was still a problem at 6.00 when the customer came to collect the car on an evening where I had a meeting that I had to be at for 7.30 prompt washed and scrubbed. So no, I have made no further tests on the heater circuit. Sorry for not being perfect, but after 34 years continuous service in industrial and automotive electrical and electronic fault diagnosis and repair I do know the easiest way is with a decent diagram in front of you. The rest of the information I gave is to give UKAT members a full idea of what I had done so far.
I really resent the 10/15 minutes comment. I often spend time looking through my records to get information to help other UKAT members (see my posts about inductance testing if you wish) to me that's what this forum is all about. I only ask for ideas on the ones that have got me a bit foxed. I don't post on the loads of cars I do every week that don't give me big problem. I do only diagnostic and electrical work but I do work on all makes and can't know the idiosyncrasies of every model, so sometimes I ask. Sorry Sean but your attitude makes me feel like I shouldn't have.
Shaun.
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