I'm stuck on the wiper wiring

[gmiles]

Okay. I'm stuck again. 74 Stepside C10. Round wiper motor with the washer pump mounted to the motor. There are two spade connectors on the washer pump and 3 on the motor. It looks like the motor has 3 wires running from the spade connectors to inside the motor: 1 white and two black. The white is on the drivers side (I'll call it #1, and #2 and #3 are black...#3 being the farthest from the driver side). The original switch had 3 spade connectors. I smoked it trying to figure out what I was doing, but have 75 C20 switch with 4 spade connectors. Both switched had 3 positions and the "push" for the washer pump

The truck has a painless harness in it but there is no provision for wipers. Neither the Haynes or Chilton manuals have helped me as the diagrams are off (wire color) and the manuals don't show the terminal numbers.

Is the system designed to have 12V running to the motor constantly and the switch grounds and connects the circuit? Does the switch have some type of resistance that changes the speed from low (high resistance) to high speed (low resitance) and is it the same with the washer pump regarding the constant 12V?

It seemed the 74 switch was grounded to the dash sheetmetal by contact. The 75 switch is plastic so one of the 4 spade connectors would be a  ground? If I can't use the 75 switch, no big deal. I'll get another 74 switch, but how is it wired up? I'll have to make my own harness for it. The 3 spade pigtail for the motor has a lt blue, dk blue and a black wire. I don't have pigtail for the 3 spade switch so I'll have to use 3 individual spade connectors.

Thanks again for your continued help.

gmiles

[VileZambonie]

Yes the 74 switch is case grounded to the dash. When the ignition switch is turned to the run position and the switch is moved to low the center terminal on the wiper board. From the center terminal current flows through the black w pink wire to the field coils in the motor and is seriesed to the shunted field ckt. Basically this is slow speed and the wiper motor is grounded via a strap to the firewall. In Hi speed current flows through the board resistor through the switch to ground. It's a very simple ckt and you will have to use the 74 switch. I don't know any other wire colors off the top of my head.

[gmiles]

So is the first switch terminal the washer pump? and the third terminal high for the wipers? Is one of spade terminals on the motor the 12V?

[VileZambonie]

Do you have an ohm meter? Easy enough to test it...I don't have a switch or schematic in front of me to tell you what the pinouts are. Sorry.

[gmiles]

Yes I have an multimeter.

[VileZambonie]

put it on the ohms scale or on a continuity test. Attach your com lead to the ground housing of the switch and then test each terminal with the Red lead to each terminal. Actuate the switch to low and there's your low terminal, then find the one with continuity in high and then the one when you depress the washer function.

[Mtrhd329]

If the vehicle did not originally have intermittent wipers you should have 6 wires for the wiper/washer.  They should be Pink, Blakc, Purple, Gray, Balck/Light blue, and Grey.  I dont have anything in schematics further than the pulse box from the switch but I went to the GM dealer service desk and they gave me their service diagrams when I couldnt find a diagram.  Hope that helps some, I know how frustrating it is trying to trace wires with the diagrams in chiltons/haynes.

[gmiles]

Thanks for all the help. I'll get a new 74 switch and figure out what post does what and wire it to the motor and washer pump. The motor has 3 spade connectors and it looks like wires run from the back of the spade connectors to inside the motor. One wire is white and the other two are black. I had to pull the motor apart to fix it soooo, I think the white is the 12V and the other two are the grounds for low and high.

Thanks again.