What plug is this? 1988 C1500 Sierra 2wd

[jcain226]

I am trying to fix a washer pump that is not working; The pump wire, as well as some other wires, lead into this harness that is pictured.

When I pulled off the cover to see what kind of connection the wires had, the inside was all melted and had this gooey tarlike substance everywhere. I pulled out some chunks and cleaned it up a little, but put the cover back on until I could figure out what the harness is for. And I didn't want to cause any damage to something else.

1st question is what is the harness to; and 2nd question is how to fix the washer pump. I changed the pump, but it is not getting power. Could it be the switch that connects to the steering wheel on the blinker bar?

Thanks in advance!

 

[deadbeat]

I have to admit I haven't worked on that model truck in a long time, but that looks like the plug where the harness goes into the cab.

 

[jcain226]

I have to admit I haven't worked on that model truck in a long time, but that looks like the plug where the harness goes into the cab.

Any idea what the melted tar like substance would be when I pulled the plastic cap back? Everything else seems to work except the wiper washer motor, so not sure what all goes into that harness.

 

[Schurkey]

Sealant, to keep water out?

On my Luminas, the power for the washer pump goes through the circuit board for the wiper motor; and there's no such thing as a new or rebuilt wiper motor circuit board--they're Treasure Yard only.

But I don't know about the GMT400 wiring scheme. Find the schematic and trace the power path.

 

[RCLB OKC]

Although I am just a hobbyist, may I add a couple of comments? I own two GMT400 trucks (one a donor for parts) and I can tell you that the junction box that you opened has a tar-like substance which I assume protects the connections from corrosion and moisture since the wires are, otherwise, exposed to the elements there on the firewall. That said, what I did was cleaned out as much of the substance as possible ( otherwise you won't get a good electrical connection when assembling the box back together). Since I was doing a restoration of my RCLB truck, I actually took the time to de-pin the box and clean each connecting pin, one by one. Since I don't have the tar-like substance to re-apply to the junction box, I used dielectric paste as a substitute. Now to your question about the washer pump. You will have to trace the power source back to the firewall; it might be a poor wire connection, a faulty switch in the steering wheel stalk, or ground. Be patient; as the above writer mentions, a wire diagram would be helpful.

 

[Dropped88]

Thats the old dielectric like grease gm used. It just gets real nasty and tacky when it gets old

 

[jcain226]

Although I am just a hobbyist, may I add a couple of comments? I own two GMT400 trucks (one a donor for parts) and I can tell you that the junction box that you opened has a tar-like substance which I assume protects the connections from corrosion and moisture since the wires are, otherwise, exposed to the elements there on the firewall. That said, what I did was cleaned out as much of the substance as possible ( otherwise you won't get a good electrical connection when assembling the box back together). Since I was doing a restoration of my RCLB truck, I actually took the time to de-pin the box and clean each connecting pin, one by one. Since I don't have the tar-like substance to re-apply to the junction box, I used dielectric paste as a substitute. Now to your question about the washer pump. You will have to trace the power source back to the firewall; it might be a poor wire connection, a faulty switch in the steering wheel stalk, or ground. Be patient; as the above writer mentions, a wire diagram would be helpful.

Thank you! I will definitely refill with the paste that you mention!

 

[jcain226]

Thats the old dielectric like grease gm used. It just gets real nasty and tacky when it gets old

Thanks! Yes, it’s definitely sticks to anything that it touches!

 

[OLD BLUE 88]

When I removed the dash to rebuild the HVAC system on my 88, my attempt to de-couple the harness at the firewall was futile. Fear of tearing something loose. Electrolytic corrosion is my guess.

 

[someotherguy]

When I removed the dash to rebuild the HVAC system on my 88, my attempt to de-couple the harness at the firewall was futile. Fear of tearing something loose. Electrolytic corrosion is my guess.

Passenger side? That's not a disconnect; it does not come apart there. It's simply a plastic clip (for lack of better term) that screws to the firewall. The disconnects on that side are at the ECM and a couple other smaller connectors inside the cab.

Richard