NJTman

I have one of those interesting intermittent electrical issues maybe one of you guys can point me in a Direction. couple years ago I replaced my fusible links with the big bad fuses Maxi fuses. haven't had any problems since.

about a month-and-a-half ago I broke down with a frozen fuel filter or so I thought. replace the filter get back on the road on my way home I realized my heater didn't work nor did my electric windows. few minutes I figured out that the fuse which head replace the fusible link failed. replace the fuse and everything was back to normal

fast forward to yesterday. truck sat for a few days and I went to start it started fine went to the roll down the windows down and they wouldn't go down. heater didn't work either.. this time I replaced it with a 30 amp fuse instead of the 40. nothing's happened until today when the 30 amp fuse failed. pop the hood put a new fuse in put a test light on a fuse and Wiggle all the wires under the hood. nothing killed the fuse. cleaned up some wires underneath the dash. Still nothing killed the new fuse. can't make the fuse die but at some point it appears it will. since I wiggled all the wires and cleaned up the wires under the hood wiggle the wires and clean the wires off underneath the dash and I can't seem to force this to fail. Do you guys have any ideas regarding how to diagnose?

cleaned all the grounds and I have a bunch of extra grounds already attached so I don't believe it's the grounds under the hood.

Thanks.....

maybe368

Hi T! I can't help with specifics, but I would bet that something hot is going to ground and it has to do with something on the circuit that that fuse protects. Maybe the fan motor inside the cab. Is there anything else that goes away if you remove the fuse? It has to be something on that ciecuit, hope that I am not being Captain Obvious here...Mark

NJTman

I completely agree. Something that....on occasion, goes to ground and. Pops the fuse. I thought the passenger door air in from cab to door was a possibility, but today I moved and twisted and opened and closed a hundred times. Nothing......

Time will tell, I guess

NJTman

Had the truck running from 7am to midnight last night. Plowed a dozen properties, and the under rated fuse keeps on ticking...

Really weird

mknittle

Is your heater motor on a relay? IF not maybe grounding through the armature?

gyman98

Had the same issue on a truck once, it was wiring above the gauge cluster in the plastic sleeve melted together. After I fixed that the PW and heater fan fusible link stayed together

N. Besonderes

The original 12GA pink/black wire, that goes from the key switch pig-tail to the fuse box, and powers the windows and A/C, was under-sized and over-fused from the factory until about 1996 when they finally offered a 10GA replacement pig-tail. If you haven't already checked this, you might have some melted insulation there against the column. Just a thought.

I got rid of my keyed switch altogether about two years ago and made a Master Power switch and an Aux Power switch with a push button to start. Also swapped fusible links for Maxi fuses. About 2 months ago, I started having the same problem you're describing. I couldn't find a short to ground so, I just wired in a re-settable 30A breaker instead of the Maxi fuse. It tripped a couple of times but nothing for at least the last 4 weeks.

-Niemand

N. Besonderes

Ima get me one of these.

torquefan

I also think you have a very intermittent short, rather than a bad ground. If it was mine, I would grab the appropriate wiring diagram in the factory service manual, locate the circuit that feeds the blower and power windows, and backtrack to find every component fed by that specific fusible link (which you have replaced by a fuse). Give the wiring feeding all those components a good visual inspection, and hopefully you can find a wire chafing on a sharp edge, or some such thing.
If that gives you no success, you can snip each branch of that circuit downstream of that maxi fuse and install a temporary inline fuse to help narrow down which branch the short might be located in.

NJTman

So thank you Mr. N. for the idea regarding that gizmo. I purchased it, but it didn't work, and I'll be saving for another day.

My issue is that the short isn't a dead one, so it did not function as it should regarding how the little needle is supposed to move about until you locate the short. Since it can take anywhere from 2 weeks to 2 months to go bad, I can't do anything with it until the short stays for a longer time period.

In the meantime, I started to poke about a bit, and found a "chewed" ground wire at the firewall above the heater blower motor. Fixed that, and will continue my search.

When we get a nice weather day, and I feel like getting busy, I'm going to separate the feed wire from the heater / window motors, as I want them on separate circuits to make it easier to diagnose things in the future. Again that's for another day.

Here's the chewed wire I found and fixed today.

NJTman

You read my mind, except for the separation of the heater motor and window motors to individual maxi fuses.... but that's what I'm gonna do.... great ideas.....

NJTman

I had read in the past about the door wiring harness being a problem in our trucks, and James PM'd me about his truck having a broken wire between the cab and door pillar. I finally decided to look in there and found that at minimum 4 wires had cracking of their coatings, but no obvious breaks. Ill be pulling that harness out and repairing those wires soon.

Thank you James1. Appreciated

Onward I march

mknittle

Mine only has two wires and both are broken on the drivers side.

gyman98

You might want to repair it right in place, that harness goes through the dash and all the way over and plugs into the passenger door. It's a dirty bugger to pull out

mknittle

There is something to be said about my roll up windows.