My first suspect would be the body ground at the mounting point.After that, I wouls make sure that the relays are workign properly. You will find 4 of them under the driver's switch panel just forward of the Switch Hub Module (SHM). Email your web addy & I'll send you a PDF of the schematic.
I may not know the answer but I can usually find who does.
Funny thing is that I haven't worked for the TBB dealer since Dec. 15th. Hopefully, I'll be able to announce a different employer in a couple of weeks. 'Til then, its 2nd shift building walls & cloth covered boxes for a local office furniture manufacturer.
I may not know the answer but I can usually find who does.