1972 FJ40 Windshield Wiring Trouble shooting help (1 Viewer)

[ceylonfj40nut]

Need some assistance with troubleshooting my FJ40 windshield wipers which are not working via dash switch. Attached pic references wires as installed on my truck. It matches what @Coolerman has on his web page.

I disconnected the wiper motor at the windshield connector and ran power directly to the motor using the female connector terminals on the motor side, the motor works. Connected +12v directly from battery to blue (L) wire on motor side female terminal and touched Blue black (LB) wire on motor side female terminal to battery neutral directly, motor turns at slow speed. When Blue Red (LR) wire is touched directly to battery neutral motor turns at high speed. This confirms wiper assembly wiring and motor are working.

When I test voltage on the blue (L) wire on the male terminal of the windshield harness that connects to the motor, I get 12v when ignition switch is in the on position and 0v when in the off position. This agrees with @coolermans website.

With everything connected (windshield connector, driver side bullet connectors, and windshield wiper switch), and wiper switched to low or high setting, neither one works. I tried to provide a direct ground to the motor/ windshield and it still did not work.

Based on @coolermans webs site for wiper switch operation (and as shown in pic) low and high speed only come on when the White Black (WB) wire grounds either the LB or LR wires.

It seems that WB is not grounding well. I tested point to point on wires shown on sketch and all show continuity.

I can trace the WB wire from the switch to the harness ground as it gets lost in the harness.

Any ideas?

I may try to run a direct ground to the wiper switch WB connector to see if it will work.

 

[73FJ40]

@ceylonfj40nut .

Two possibilities to resolve your problem:

1. Definitely ensure the switch and motor are well-grounded.

2. Double check the connector on the switch to make sure it isn't reversed. It goes on both ways.

 

[ceylonfj40nut]

@ceylonfj40nut .

Two possibilities to resolve your problem:

1. Definitely ensure the switch and motor are well-grounded.

2. Double check the connector on the switch to make sure it isn't reversed. It goes on both ways.

Thanks. I am going to verify #1 above. Wrt #2, I am aware it is a keyed connector and that is in correctly. It matches the wire color termination on @Coolerman website.

 

[Engineer8000]

When you did this, was the switch connected, what position was it in?

"I tried to provide a direct ground to the motor/ windshield and it still did not work."

 

[73FJ40]

"Wrt #2, I am aware it is a keyed connector and that is in correctly."

You are very fortunate. My stock, original connector could attach both ways.

 

[ceylonfj40nut]

When you did this, was the switch connected, what position was it in?

"I tried to provide a direct ground to the motor/ windshield and it still did not work."

Switch was in low speed, ignition in on position.

 

[Engineer8000]

Sorry, I got busy with taxes and forgot about this. I would proceed as follows:

First verify your wipers are wired like this - take note of the LB/LW swap at the windshield connector for the low speed brush and park switch:

(compliments of @Coolerman)

Based on your statement:

"I disconnected the wiper motor at the windshield connector and ran power directly to the motor using the female connector terminals on the motor side, the motor works. Connected +12v directly from battery to blue (L) wire on motor side female terminal and touched Blue black (LB) wire on motor side female terminal to battery neutral directly, motor turns at slow speed. When Blue Red (LR) wire is touched directly to battery neutral motor turns at high speed. This confirms wiper assembly wiring and motor are working."

Touching motor side LB wire to battery neutral should not get you slow speed.

Once I understand your wiring we can make some progress.

 

[ceylonfj40nut]

Sorry, I got busy with taxes and forgot about this. I would proceed as follows:

First verify your wipers are wired like this - take note of the LB/LW swap at the windshield connector for the low speed brush and park switch:

(compliments of @Coolerman)

View attachment 2980947

Based on your statement:

"I disconnected the wiper motor at the windshield connector and ran power directly to the motor using the female connector terminals on the motor side, the motor works. Connected +12v directly from battery to blue (L) wire on motor side female terminal and touched Blue black (LB) wire on motor side female terminal to battery neutral directly, motor turns at slow speed. When Blue Red (LR) wire is touched directly to battery neutral motor turns at high speed. This confirms wiper assembly wiring and motor are working."

Touching motor side LB wire to battery neutral should not get you slow speed.

Once I understand your wiring we can make some progress.

View attachment 2980946

My sketch above is what is installed and is a schematic similar to what you attached from coolerman. I will check slow speed setting to see if I indicated a wrong wire color for slow speed.

 

[ceylonfj40nut]

Checked. Error in my earlier write up. Checked by connecting motor directly to battery

LW= slow speed
LR= Hi speed.

LB/LW switch at the connector matches coolerman schematics

 

[ceylonfj40nut]

Connected the wiper back on. Hard wired the ground terminal from the switch directly to the battery and switch and wipers works as it should from the switch in off, low, and high speed. Looks like WB ground wire from switch is not grounded. Need to trace it back from switch to fuse panel area.

 

[ceylonfj40nut]

Chased WB wire from wiper switch. Looks like it is grounded via the emissions control module. I hard wired WB wire terminal on emissions computer to -ve battery terminal and wipers works like it should via switch.

 

[Engineer8000]

Good going figuring it out, thanks for closing the loop. If you have a moment, can you explain what this looks like:

" Looks like it is grounded via the emissions control module."

 

[Engineer8000]

Never mind. I pulled out my 73 harness and hooked it up to one of the emission computers I have. It seems crazy that the whole thing is grounded through that one terminal on the computer.

 

[Engineer8000]

I don't see any other ground lugs.

 

[ceylonfj40nut]

Yep it’s crazy. Everything works! So glad. Here is the rig. My son @Cowboy45 will be driving it to school. We needed to get it inspected. Got this and the reverse light wired as required per FSM. My boys are getting better with their hands.

 

[Engineer8000]

Those seats look great.

 

[Engineer8000]

And great patina, I'm jealous.

 

[ceylonfj40nut]

And great patina, I'm jealous.

Yea. We love this truck. Recent acquisition.

 

[KingAir Driver]

Great looking 40! Good to know the motor grounds through emissions as mine is disconnected and the wipers weren’t working as well.

 

[ceylonfj40nut]

I cut the ground wire from the emissions control male connector and spliced a connector to it so I could bolt it to a ground on the footwell. The emissions control ground path is far inferior compared to the spliced ground. Lights are much brighter and wipers move with great umph!!!! Makes sense to find a better ground path.

Note, I don’t care about the emissions computer because it is does not use the fuel cut off solenoid circuit and is “desmogged” as a 350 motor.