Porsche Repair: 944 quirks continued, fog light switch, bringing power

Question
Hello. I've been working on that 944 heater problem and have reduced the rat's nest to almost factory condition. I took out the "carbon fiber" center console and unplugged everything. All that's plugged in is the a/c control, fog light switch, and heater control. I unplugged the oil/clock gauge harnesses, and 3 small wires were already disconnected (grn/brn/blu i think)and I have no idea what they are for.  there is another harness that was never connected (it has some sort of diode or somtething on one of the wires) and I'm not sure what its for. Maybe this could be the problem? I checked all fuses, and it looks like theres no relay for the heater fan. Maybe I'm mistaken, so your continued help is greatly appreciated. Thanks again!

-Steve

Answer
Hi Steve,

Good work!.  Obviously this would be more fun if I was there seeing what you're seeing.  We are are having fun, right?

I'm only going by what the wiring diagram says and a bit of logic thrown in for good measure....there really "should" be a heater blower relay.  

The blower relay (it looks like it could be replaced if it's mising, with a very common bosch 25/30 amp relay, <$5, rather than a Porsche $pecial relay) gets power from a red wire from fuse 9 (25 amps) and is grounded with the brown wire.  When activated the relay sends power to the blower via another red wire.  I'm still trying to figure out how the two black/purple wires are involved, but they are.  I'll have to get back to you on this.  You do have two black/purple wires together in a harness perhaps?

Anyway, on the other side of the blower itself (remember, one wire is red bringing power) the brown wire goes to the resistor and the resistor is controlled by the blower switch's three output wires: brown/black, yellow/brown, and brown/white.

Regarding that harness with the diode...tell me the colors of the wires and I'll try to figure out what that's for.

Dave