620 heater fan blows constantly

[BFRascal]

New to this forum and the 78 Datsun 620 I’m working on. Blower fan runs on high as soon as the ignition switch is turned on even though the fan switch is in the off position. The two wires from the fan switch run to a round aluminum tube and has zero continuity (capacitor maybe). There is a resistor on the heater housing and it test with resistance. The truck seems to put together with used parts and has a number of loose wires both under the hood and dash. The wiring diagram I’ve seen doesn’t show the level of detail required to understand how to run the wires properly. The heater switch has three wires black, white and white with red. The white wire has a black wire crimped to the spade connector. If anyone knows how it should be wired please respond with a simple sketch. Thanks. Jim

[datzenmike]

Power is supplied to the heater fan (Blue wire) as soon as the ignition is turned on. It's up the the fan switch to connect it to a ground to turn it on. To get different speed other than high the switch selects a wire coil resistors to ground. If your fan is on at all times then the switch is stuck on on, or the wire from the electric motor is pinched and grounded turning it on.

[BFRascal]

Thanks DatzenMike

I cleaned the switch. I now have high speed fan but not slow and the white and white/red wires are attached to the aluminum canister device (resistor I assume). There is no resistance across the canister terminals. Do you know the part number for that part?

[datzenmike]

Slow has to go through the wire wound resister to get to ground. It's mounted on the gas pedal side of the fan unit so the air can keep it cool. Just pry it out and take a look at it.

 

 

Measure the continuity when disconnected. You can probably crimp it back together. The part number is 27100-M0200 but unlikely they are in stock.