NEED HELP with wipers on 1973 C15

[mjaxtreme]

Hi Guys,

I know there are a ton of threads on wiper issues, but I couldn't find any particular to 73 models so I figured I'd ask for help.

I bought a 1973 GMC C15 and the wipers were dead. I went to O'Reilly and bought a reman washer motor and put it in a few nights ago. Got nothing.

With the ignition on or off, I have power coming into the motor on the center terminal (yellow wire w/ black stripe). the motor also has a green/black wire and a tan/black wire which I assume control the hi/low speeds or are grounds.

The switch is dash mounted and 3 wires going to it (solid black, light blue, and dark blue).

I was able to turn the power on and ground the two outer terminals on the motor and it began to turn.

I am assuming my issue is either the switch or the wiring between the switch and the motor, I just don't know where to start or if there is a way to test the switch.

Any help is greatly appreciated!

 

[bucket]

Going off my poor memory, the wires from the switch are a ground (black) and one blue is for low and the other is for high. You should be able to unplug the harness from the switch, and jumper one or the other blue wires to ground and see if the motor runs. If so, the switch is bad. BUT, I'm pretty darn sure there should be a fourth wire, to activate the washer pump?

 

[chengny]

I am assuming my issue is either the switch or the wiring between the switch and the motor, I just don't know where to start or if there is a way to test the switch.

This first test will isolate the problem to either the switch or the interconnected wiring. If it shows that the problem is in the wiring, there is another test to determine which wire is the cause:

Like you know, there are three wires connected to the switch. Pull them off.

Disregard the dark blue with a black tracer (B/DBL), that is ground from the washer pump and not part of this test. You will only be working with the B/LBL & the B.

Just as info: the black lead connected to the switch changes from plain black to black/white at the firewall - so it shows as B/WHT at the wiper motor connection. The black/light blue stays the same color all the way from the switch to the motor.

So, with the wiring disconnected from the switch and the washer power (B/DBL) lead set aside, you will have only two leads left (the B & B/LBL).

First you have to understand that the power to the both of motor windings (hi/lo speeds) and the washer pump is direct from the fuse block to the wiper/washer on the B/Y lead - it doesn't pass through the switch. It is connected at the center terminal of the wiper motor. That center terminal is connected to the hi/lo speed windings. Also (from what I can see in the dwgs), the center terminal is internally jumped over to the pump. So, with power always available on the positive side of both motor windings, the wiper motor will operate if one or both of the winding's negative sides are grounded. That is normally the function of the dash switch - which you will be replicating.

The dash switch provides the last bit of the ground path through it's body, the dash mounting plate and associated fasteners. It might save you a ton of time and aggravation if you check the switch first. Make sure it is tightly fastened to the dash.

Find a way to temporarily connect the two remaining wires - that were attached to the switch - to a good clean ground point.

The actual test is pretty simple and quick:

1. If both the B & B/LBL leads are connected to ground, the motor should operate on low speed.

2. If only the lead connected to terminal pin #1 is grounded, the motor shifts to high speed. Problem is, I don't know - and the dwgs don't show - which leads are connected to the 1 & 3 pins. You'll have to look at the motor connections to determine which color goes to pin 1.

This dwg shows the pin number designations:

You must be registered for see images attach

Notice that they are doing essentially the same test as you will do - only without all the jumpers. Difference is, they are testing the motor (and parking operation). But since you just installed a new wiper motor, you can skip that part and jump to the switch/wiring part of the test.

Both wires grounded should result in low speed operation

Just the wire from pin 1 (whichever color that is) grounded, you get high speed.

 

[mjaxtreme]

Test

This is great. I will try the test when I get home from work. Thanks!

 

[mjaxtreme]

Was able to work on it tonight, and after a bit more troubleshooting, finally found that it was a bad ground connection from the switch body to the dash. Got it cleaned up and its working like it should. Thanks for the help guys!

 

[chengny]

Did you see this:

The dash switch provides the last bit of the ground path through it's body, the dash mounting plate and associated fasteners. It might save you a ton of time and aggravation if you check the switch first. Make sure it is tightly fastened to the dash.