Further update.

1. Instrument lighting "fixed". The rheostat is worn and just needs careful adjustment.

2. I have ordered a new duovalve as it did not respond to testing (it is getting 12volts and does not appear to work, no pulsing). This was expensive (GBP227.96 incl tax) but available soon, whereas the repair kits were expensive (GBP180 plus tax for the pair) but not available for a while. Also, the duovalve can be returned if not required.

3. The cruise control is not the switch. I note there are a number of modules, any ideas which it might be?

4. The seat is "fixed" in the sense that the problem was traced to the control unit, which has been by-passed with a pair of relays. So the seat works, but not through the control unit. No doubt there is some reason why this might be a bad idea, but I will be careful. I suppose it means I have not got the memory function. One for the future, perhaps.

5. I suspect this is the blower aspirator pump for the cabin temperature sensor. I do not think it is related to the lack-of-heat problem (for the reasons stated above and because there is never any heat rather than merely slow changes in temperature) but it will have to be fixed. I note it is not horrendously expensive. I wonder how easily accessed it is.

Further comments and assistance welcome.

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JJ Rodger
2013 G350 Bluetec
1999 SL 500
1993 E300 diesel T
1990 190