Anyone near me want to play with diagnostics?

[re-tread]

Hi David,

As you say there must be a subtle difference in the outputs of the aftermarket panel that messes with the V8 HVAC signals to the heating valve. There is a HVAC ECU on V8's that I can't find listed as a standard 75/ZT item. Unfortunately as Rimmers no longer provide part numbers on their listings for NLA items it is difficult to do a conclusive search, but I cannot see the same item on the 75/ZT heater assemby diagrams (Item 5 on the V8 diagram).

I have often thought that gremlins in this additional ecu is what causes heating problems on some cars and not others, or possibly just a dodgy connection to it. The HVAC has always worked perfectly on #431 (touching wood as I type!) but fitting the aftermarket panel showed the ecu was sensitive to different inputs

Mike

If the ECU you are thinking about is the one mounted on the heater box under the dash then it is part number JFW000011. I was hoping that changing that would sort out my heater gremlins but alas no.

[Burwell Mike]

If the ECU you are thinking about is the one mounted on the heater box under the dash then it is part number JFW000011. I was hoping that changing that would sort out my heater gremlins but alas no.

Yes that looks like the one! Oh well there goes my theory about the HVAC ecu causing the problems. Sorry that you had no joy after changing it Dave.

Mike