Electrical and Windshield Washer Experts Needed

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F

FJ40mod

Joined
Feb 18, 2026
Threads
4
Messages
17
Location
Coastal Sea Level
So, I have successfully resolved the predominance of the rig’s Electrical gremlins.

Only the aftermarket gauges messes and the washer system remains.

I do not have power to the pump. Where, physically, does that power wire feed from the fuse box? Is it it’s own separate conductor from the box to the pump, or is there a connection or joints somewhere else?

1973 FJ40
 
The wiper switch is rotated to the right to turn on the washer in my 72. The wipers do not need to be turned on. I think there is a wiper fuse 15A 3rd up from the bottom.
 
Yes, I have my wipers working and cleaned up the ground contact at the switch. I have switched ground at the pump, but no power.
 
Test the pump with a hot wire from the battery + and a ground wire. You will want to consult the wiring diagram to know what each of the wires at a the plug are for. Pump works - then wires are bad or the switch is bad.
 
The white OEM plug is 2 wire and comes out the harness below the hydraulic master cylinders clutch/brake. The washer bottle is held in a slot on either the cowl or the fender below the MC's.
 
The wires are like 3' long from the plug to the wiper switch, trace them. I'm not sure but I think it is a ground connection made by rotating the knob. So the switch body needs to be grounded (IE mounted and making electrical connection the cab) which makes contact to the battery neg-. I bought new 2/0 cables for my battery. The black neg goes from battery to an engine bolt. From that engine bolt I ran the old 2 gauge cable to the chassis ground under the front brake "T". From the front brake "T" I ran a black #10 wire up to the cab.

I are not clear what information you need
 
The Blue (L) wire from the 15A fuse is spliced under the dash and goes to the wiper motor, switch, and then through the dash to the pump. With the ignition on, the L wire at the motor should have power. With the knob turned, the LY provides ground through the switch to the fluid pump.
 
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Thanks for all the input guys, but I really just need to know where the pump power physically connects to the feed shared by the motor.

I have AC in the truck and someone put aftermarket gauges in it, and covered the factory hole in the dash in the process. There is no room to be physically chasing wires without removing the AC system and/or cutting the das out. Neither of those things are going to happen any time soon.

I am attempting to avoid simply running another wire as I would rather fix what is there already.
 
We’ve tried to help, and I’m not sure how much more clear we can be. The splice is under the dash in the harness. There isn’t a connector for it.

Since a previous owner has added wiring and covered the factory hole, then we can’t tell you where it’s going to be. There’s no way to know since it has been modified.

You say you don’t want to chase wires, but you want to use what’s already there. Those things are mutually exclusive since you don’t know what’s there.

Here’s an example on a ‘67 (circled in red on the right).

IMG_3222.webp
 
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nabbasi said:
We’ve tried to help, and I’m not sure how much more clear we can be. The splice is under the dash in the harness. There isn’t a connector for it.

Since a previous owner has added wiring and covered the factory hole, then we can’t tell you where it’s going to be. There’s no way to know since it has been modified.

You say you don’t want to chase wires, but you want to use what’s already there. Those things are mutually exclusive since you don’t know what’s there.

Here’s an example on a ‘67 (circled in red on the right).

View attachment 4096131
Click to expand...
I’m sure it’s just a simple matter of wording.

When I say physical location, I mean a specific point where a physical thing is located. “Under the dash,” is simply not a physical location so much as a general area. An area that I have described is not easily accessible.

If someone knows where it is, that’s great information for me and anyone else who might search for this in the future.

If no one knows, that’s great to know too.

But no, I am not pulling an entire harness out of something that I am putting life back into, for a washer pump power lead that someone may know where it ties in to the circuit.

The harness has not been modified. Gauges can be added without modification of a wiring harness.
 
Without having stripped a wiring loom apart, there is no clear answer.
Since the wiring for the motor runs up the left side of the windshield, and the pump is on that side as well, I’m guessing they splice up under the dash near the peddle assembly.
 
There are wire tracer units. Clip on a wire and follow the signal. Personally I'd just put in a momentary switch and add two wires to the pump.
 
charliemeyer007 said:
There are wire tracer units. Clip on a wire and follow the signal. Personally I'd just put in a momentary switch and add two wires to the pump.
Click to expand...
Yep... In general the wire should be the same color throughout the harness. I think I'd just set your volt meter to test continuity and start with similar color wires near the dash switch and at the motor. You should be able to narrow it down from that without pulling out the harness. However....its not really that hard to pull the harness out. I pulled mine out...traced a wire...and put it back within 4 hours....including unhooking and rehooking everything. Granted...i'm getting some "miles in the saddle" doing this so it'll take longer the first time.
 
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