Fresh air blower

[padraic emparan]

Hello, I am new to the group but let me say that I have a 1972 July 914 1.7 with dual webers. I have had some problems with my restoration of late because I cannot make the fresh air blower fan power on. so i am asking the great minds out there to aid me: i know that the fan works because i bench tested it. the switch seems to be fine, and cables work fine. there is power from the red wire that attaches to the blower switch. but when i attach the power wire to the switch (red with white stripe) and make sure the brown wire (ground) is attached, and move the top toggle to engage the fan, there is a spark, and then the fuse (#8) blows. I have tried this a number of times and seems to get nowhere. #8 is horn, wipers, and cigarette lighter as well. all work except the cigarette lighter, as when i have attached the wires and put the antiquated lighter in to engage, there is no heat, but power to the red black wire, i am assuming the unit is broken, and is not worth the trouble at 50 plus dollars for a new one. but i would like to get the @#$^ blower working. where am i going wrong? i pulled the fuse pannel off and though there might be a problem with the wiring there, but everything else is fine, but the fuse shorts out when i engage the switch, anyone with some ideas?

[lars s]

I think you might have a problem at the fan switch. The red with withe stripe wire should ONLY be connected to the signal lamp in the switch. The other 4 wires at the switch (brown + 3 withish) brings earth (minus) to the motor since the motor is directely (ower ignition) fed with +12V (by its own red/white wire).
So the fan is controlled by the switch earthing the different (whitish) speed wires insted of giving the speed wires +12V which may be a little odd.
I have a '72 wiring diagram if You dont have it.

/Lars S