I don't think the relays use diodes for supression. If they were to use diodes, the relays would have
be polairty specific. Generally, there are preferred arrangements for wiring of relays but it is not polarity orientated. In the relays I've encounted, there is a low value resistor in parrallel with the winding to act as emf supression.
I'm not confident that the relay will be your cause of ire! I'm not to know the condition or history of your car but having rebuilt the switch assy on my car, I remember the loom path in the centre of the car as not being very ideal.
I read in these forums occasionally of wiring abnormalities for one fault or another and generally am left with impressions of previous owners and their botch ups, wiring faults from install jobs, alarm configs etc. all seem to be coming home to roost, so to speak.
Being a conv, is there any chance of corrosion effects from a possible deluge of rain in the past perhaps or similar?
Was the switch you installed new or used? ( TAKE 2
...Did you replace the switch?)
Just some thoughts......
14/09/05: I stand corrected. I went and looked in the bible and observed the arrangement being different for the convertables. Sorry for crapping on.
P.S. The Ashes are yours!