Fan pull switch question

[delta21]

I have a '78 40, the heater fan only works in the low position, when I pull it out to the hi position, the fan does not work, the head lights dim and the red seatbelt dash light comes on and then after about 10-15 seconds of this the fuse blows. So there must be a sort somewhere. Anyone have any expierence with something like this?

 

[green71fj]

sounds like the wiring gremlins have gotten to you cruiser. first pull the switch out take it apart clean it. if thats not the problem your gonna have to look through all the wires, sounds like a dead short to me, trace the wire that operates the fan you'll find it. I had the same wiring problems a few years ago,one after another, i ended up replacing harness with a painless harness

 

[delta21]

OK, I just pulled the switch and cleaned it up. It looks fine and seems to have good contacts, so now I'll start the wire chase.

 

[Coolerman]

If the headlights are dimming then you have a lot of current flowing somewhere. The 15 amp fuse that controls the heater blower, also controls the seat belt warning relay, backup lights, all gauges except the amp meter, and finally the brake warning light.

I would suspect that the high speed wire for the heater (Blue/white) has melted somewhere in the harness and is shorting to the Black/Yellow wire of the seat belt warning light. Try disconnecting the blue/white wire from the heater resistor on the motor, then jumpering +12V to the place you removed it from. If the blower motor works then you know the blue/white wire is shorted somewhere in the harness. To find it you will have to remove the tape from the harness, OR run a harness bypass wire for the heater hi position.