Wiper motor wiring

[mars636]

I am trying to figure out where the yellow wire that comes off the wiper motor/ pump and then goes through the firewall terminates. the yellow wire comes from the harness then goes into the wiper motor then jumps over to the pump then off the pump it goes through the firewall.

[ray_mcavoy]

Welcome!

What year is your truck?

For many years, the yellow wire is typically the +12V power feed for the wiper motor. It starts at the "WIPER" fuse and runs directly to the motor. The short yellow jumper wire then feeds power to the washer pump solenoid.

The other wires on the wiper motor & washer lead back to the switch. The switch completes the circuit(s) to ground to operate the motor & washer.

For 1972 & earlier trucks with the wiper motor mounted up under the dash, none of the wiper motor wiring originally passed through the firewall. 1973 & newer have the wiper motor mounted on the engine side of the firewall and the wiring does pass through the firewall bulkhead connector.

[mars636]

Originally Posted by ray_mcavoy

Welcome!

What year is your truck?

For many years, the yellow wire is typically the +12V power feed for the wiper motor. It starts at the "WIPER" fuse and runs directly to the motor. The short yellow jumper wire then feeds power to the washer pump solenoid.

The other wires on the wiper motor & washer lead back to the switch. The switch completes the circuit(s) to ground to operate the motor & washer.

For 1972 & earlier trucks with the wiper motor mounted up under the dash, none of the wiper motor wiring originally passed through the firewall. 1973 & newer have the wiper motor mounted on the engine side of the firewall and the wiring does pass through the firewall bulkhead connector.

My truck is a 1967, it is the factory wiring, it has yellow coming from the wiper fuse then to the motor the short jumper to the washer pump then from that connection it goes through the firewall into the engine bay. All of the wiring diagrams i seen do not show it.

[ray_mcavoy]

Originally Posted by mars636

My truck is a 1967, it is the factory wiring, it has yellow coming from the wiper fuse then to the motor the short jumper to the washer pump then from that connection it goes through the firewall into the engine bay. All of the wiring diagrams i seen do not show it.

Yeah, '67 shouldn't have any of those yellow wires going through the firewall.

Some folks use the power feed to the wiper as a power source for an electric choke when they swap carburetors or add an electric choke to an existing carb. Or someone might have discontinued the original washer pump and added an electric pump mounted somewhere under the hood. Either of those could explain the yellow wire going through the firewall. And if they used matching colored wire and OE Packard/Delphi terminals it could appear to be part of the factory wiring.

At least that's all I can think of anyway. I don't think there were any factory options that would have resulted in a branch of that yellow wire running out through the firewall.

[mars636]

Originally Posted by ray_mcavoy

Yeah, '67 shouldn't have any of those yellow wires going through the firewall.

Some folks use the power feed to the wiper as a power source for an electric choke when they swap carburetors or add an electric choke to an existing carb. Or someone might have discontinued the original washer pump and added an electric pump mounted somewhere under the hood. Either of those could explain the yellow wire going through the firewall. And if they used matching colored wire and OE Packard/Delphi terminals it could appear to be part of the factory wiring.

At least that's all I can think of anyway. I don't think there were any factory options that would have resulted in a branch of that yellow wire running out through the firewall.

Thanks so much for your help, they did use the factory connectors and it is just an extra jumper that i can unplug then plug the other end into the wiper. then just remove the wire that goes through the firewall.