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Username Post: 94 Chevy C3500 - Small Electrical Gremlin        (Topic#372637)
Posts: 37

Age: 28
Loc: North Carolina
Reg: 08-13-16
02-23-23 11:23 AM - Post#2854898    

Hi all,

I just picked up a manual 350tbi 1994 C3500 Dually extended cab w/ 8ft bed, yesterday as a heavy duty work truck around the farm. Truck used to be a diesel, previous owner put a 350 in it.

It runs and drives strong, but intermittently the power windows, wipers and cluster gauges (except for the RPM gauge, RPM always works) will stop working if it rains. After a few minutes they usually come back.

I am thinking there must be a short somewhere where all of these wires are bundled together since it affects all of them. Any suggestions for where these wires get bundled together? Is it behind the firewall, or do all these wires come together in the engine bay?

Since it affects more than just power windows I think it is unlikely the short is in the door jam which is a common area for shorts to happen.

Blue Collar Farmer and Computer Programmer

-Way back in a Holler in Southern Appalachia

Edited by rachki on 02-23-23 11:44 AM. Reason for edit: No reason given.

Frequent Contributor
Posts: 2072

Loc: Orlando Florida
Reg: 07-09-18
02-23-23 11:42 AM - Post#2854900    
    In response to rachki

I doubt that it is a short, otherwise, you would pop a fuse.

It is more likely a bad connection where you have power loss when water gets on the wiring or you have a very poor ground.

People fear change because it threatens what they know, or what they claim to know.

Bill K.b 
Senior Member
Posts: 4529

Loc: upstate NY
Reg: 10-24-05
02-24-23 06:36 AM - Post#2854939    
    In response to Tony1963

On the vans and square body trucks the PW/PL wiring had an add-on harness across under the dash that plugged into the fuse box and grounded under the left upper cowl. I would have a look and see if these are the same and check the ground on it.

Those who can, do. Those who can't, criticize it on the internet.

Driving 2002 Express 2500
2002 Express 2500 extended
1988 G20 conversion
1993 GMC 3500 dually

Plus cars for swap and sale
& yes, I once tried a frame swap on a 51 Chevy.

Senior Moderator
Posts: 29669
Loc: Texas
Reg: 08-01-03
02-24-23 08:53 AM - Post#2854949    
    In response to Bill K.b

That's definitely an odd one but as others have mentioned your suspect is a ground.

The cluster wiring itself grounds with a single black wire with a ring terminal end, attached to a metal tab under the dash using one of the screws that also attaches the ALDL connector under the dash. It's probably just fine, but other larger grounds in the truck are suspect, especially since it's an engine swap. Equally, I wouldn't suspect the accessory wiring for the PW/PL where it attaches at the convenience center - driver side firewall inside the cab - since the cluster also goes out, but obviously no harm in checking it.

The main factory grounds for a small block in a '94 include these critical points:
1. Battery negative terminal to the engine (usually connected to a stud on the intake manifold, up front)
2. Battery negative terminal smaller wire to the passenger fender side
3. Rear of passenger side cylinder head, braided strap to the firewall near heater hose connections
4. Same spot on firewall as #3, another braided strap down to the frame near the upper control arm
5. Two grounds from sensor/engine harness to the stud on driver's side of thermostat housing on intake (# and wire colors vary with year)

WAG says you have a missing/loose/damaged ground somewhere and it's accidentally finding a different path, which can ultimately cause other issues. Those braided straps at the back of the engine often get overlooked/forgotten, and the straps can rot and fall apart.


06 Silverado ISS / 06 Silverado SS / 06 300C SRT8 / 93 C3500 dually

Posts: 37

Age: 28
Loc: North Carolina
Reg: 08-13-16
03-17-23 05:31 PM - Post#2855888    
    In response to someotherguy

Thanks all, sorry for the slow response. Poultry season is ramping up on the farm and have to get that work done before truck work, but I have been using your suggestions to poke around.

I've found a cut ground wire by the battery, am going to replace it once I find time and will see if that solves the issue. If not will try those other spots you mentioned Richard.

Blue Collar Farmer and Computer Programmer

-Way back in a Holler in Southern Appalachia

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