Sean,
Thank you for taking the time to reply but on this my perspective is completely different:-
I have already found and repaired three seperate faults on this car. I like to think these were found by basic checks.
The P0130 code in Autodata gives two outcomes and whoops I did not immediately identify it as a heater fault, I made a snap judgment and thought of it as a no activity fault, I think in all honesty I interpreted as a P0170 code, I'll hold my hands up to that one.
It was only when I was half an hour late and trying to get off home that I then identified this REMAINING fault as a sensor heater issue with no time to investigate there and then.
My statement 'Any ideas or magic bullets welcome.' was meant as a little humour, perhaps I should have put it in quotes or popped a smiley on the end. Sometimes there are common problems (corroded wire splices in nearside sills on Audi A4s spring to mind)which after you have spent a great deal of time in investigation turns out that "everybody in the trade knows that". It is just possible that there is an inline splice in the loom splitting the heater supply that corrodes through due to runoff from the windscreen and it is possible that a UKAT member knows this and I don't. I was told "there is no such thing as a stupid question, but the one you didn't ask and should have".
You gave advice on identifying heater wires, to the best of my recollection they are all the same size, on the sensor they certainly are, it is in my hand now. For future information they are the grey and the white wire on pins 3 and 4 of the connector, found this information out later whilst researching the problem (Ilexa forum I think).
I can and will find the fault without a diagram, and could in a field with my swiss army knife and a sidelamp bulb on wires if I had to, but I am not in the habit of making things really hard for myself if it is not necessary.
Useful information you could have provided if you are so knowldgeable on these is whether the heater supply is high side or low side switched, fed from the fuel pump relay or whatever.
You say I am not willing to invest 10/15 mins in testing, as I have said I had no further time at that point and had to let the car go, it's due to get more time on Tuesday.
"EXHAUSTED ALL TESTING" You can spend hours doing that, sometimes it's better to talk to others who will recalibrate your personal compass and get you restarted in the right direction, that's what I thought I was doing.
What I will need to do is get the car jacked up (I don't have a ramp as for 99% of my jobs they are a liability) Put some long test leads on the heater connector and continuity test back to the PCM and supply point, it would just be nice to know where they are.
In the lack of other information I would surmise that the heater live is fed from the fuel pump relay and the ground side is switched through the PCM, do you have anything concrete to add to this?
In hindsight I should have used my normal long-winded and methodical approach of "test every little thing" But as I put at the beginning I was hoping to keep the costs down, c'est la vie.
I always take help and advice, not so keen on slagging off, sorry.
Shaun