First gen dodge wiring issues

ProbablyBroke

ProbablyBroke

does not torque to spec
Joined
Nov 7, 2012
Location
Reidsville
I have a 1991 dodge d350 that has problems with the headlights turning off randomly. At first the headlights would randomly turn off after about 45 minutes of being on. I deleted all of the fusible links under the hood using a fuse block, and a few circuit breakers. The headlights still randomly cut off. They will cut back on after a while but now the ABS and Parking brake lights illuminate on the dash while the headlights aren't working and as soon as the headlights turn back on the abs and parking brake dash lights turn back off. Any idea or suggestions on where to go from here. I'm all ears. Thanks
 
^^^ The above is correct... 1st Gens are known for wiring problems. However, since the problem you describe is mainly involving headlights and instrument panel. Personally, I would suggest looking real close at the light switch itself before digging too hard into that fuse block.
 
Granny said:
^^^ The above is correct... 1st Gens are known for wiring problems. However, since the problem you describe is mainly involving headlights and instrument panel. Personally, I would suggest looking real close at the light switch itself before digging too hard into that fuse block.
Click to expand...
I would say with the abs and brake light coming on at the same time that the headlights go out that the problem is probably not in the headlight switch itself. I had one that I worked on that the windshield wipers wouldn't work and the windows would randomly roll up or down by themselves. Ended up being in the fuse box, replaced/repaired the bad sections and in the block and both issues were fixed.
 
Junkyard Dog said:
Build or buy yourself a headlight harness with relays. Dodge ran the headlight wiring thru the switch for some genius reason.
Click to expand...
Cost savings, but if it has lasted 27 years it must be atleast a decent switch.
 
Stuntman Autoworks said:
Cost savings, but if it has lasted 27 years it must be atleast a decent switch.
Click to expand...

Also know to cause random dash fires in first and second gen trucks.But back to the original problem, it deffiently sounds like a bad connection or crappy wiring. If it's trying to short out it maybe back feeding thru a ground causing other stuff to illuminate. Also check under the column plastic crap to make sure nothing has rubbed thru.

If/when you build yourself a headlight harnness your wonder why you didn't a long time ago.
 
I failed to include that it's not just the headlights that cut off when the dash brake and abs lights illuminate. It's all my lights. I haven't pulled over to see if my actual rear brake lights are affected. Thanks for the suggestions so far. I have a new aftermarket headlight switch, that I plan to install regardless. I would really like to use the factory wiring ( even though I know it's garbage from the factory) if at all possible. I'm starting to think the back feeding a ground could be the issue. Just gotta crawl up under there when it's done raining and see what I see.
 
If it's got a amp gauge in the cluster, I'd start there. Ignition switch next place. I can pull up the factory wiring if that'd help you.
 
It does have an amp gauge. It reads right at 14ish when the the truck is running and doesn't fluctuate when this condition happens. The condition I've described will happen maybe every 5-7 minutes while driving. Headlights will cut off, brake and antilock lights will go on, and then it will go back to normal after a few minute, then it will happen again a few minutes later. I did unplug a small single black wire that plugs into the side of the factory light switch. As a result, I can't turn the dome light on with the headlight switch. I took it for a little ride up the road and didn't have a problem. Does that change anyone's diagnosis?
I might get the LMC Heavy duty harness like @Junkyard Dog suggested as a preventative measure. I've seen too many pictures of dash fires in these trucks.
 
If the brake light circuit loses power it will cause the abs and dash brake lights to come on. Since you lose running and head lights the same time as the abs and dash brake light come on I would also look at the fuse block first, specifically checking for chaffed wires or bad grounds. 72 to 93 Dodges are notorious for poor wiring with a chief cause being insufficient grounds. One of the first things I do on every one I get is add more grounds.

Duane
 
Voltmeter != Ammeter

Voltmeter reads voltage (9-18 typically)
Ammeter reads charging/discharging (--x/0/+x).. might just be the older older Dodge that has ammeters (all the power ran through the amp gauge, bad for failing due to poor connections)

Head light switch connectors I've seen melt in jeeps.. bet Dodge is the same setup. The single black wire with a spade is the ground side of the dome ckt.
 
I fooled with this truck some this weekend. Replaced the headlight switch and thought I was good to go. The lights didn't randomly cut off at all on Saturday, and seemed to be trouble free until I left at 5:30 Sunday to drive 4 hours across the state.
 
Was the connector melted at all? Corroded terminals?

On the Jeeps, there is a headlight plug at the front left of the engine compartment that sometimes is corroded/compromised.
 
ProbablyBroke said:
I fooled with this truck some this weekend. Replaced the headlight switch and thought I was good to go. The lights didn't randomly cut off at all on Saturday, and seemed to be trouble free until I left at 5:30 Sunday to drive 4 hours across the state.
Click to expand...

If it were me, next place I would look would be the ignition switch.
 
Does anyone know if these headlight switch is thermally protected from over heating? I'm going to install the relay harness to try to take the load off the switch. That's the next plan of attack. I spent a lot of time under the dash this past weekend and although it's a bit of a mess under there, everything seemed to be unchaffed.
 
I love my old Dodge trucks, but the wiring sure does suck! Glad you got it sorted out.

Duane
 
Back
Top