I posted a while back about some weird electrical issues I was having on my '84 F-150, 351W HO 4x4. Today they got worse.

I cranked up to go to work and the radio popped and cut off. It has done this before when I cranked up, so I didn't think much about it. Turned it back on, it came on, but no sound and then I smelled burning wires. I shut down and started investigating. Had the radio fuse burning hot, which I knew it would do since it is WAY higher than it should be (30 amp is what was in there when it is supposed to be a 5 amp, but nothing below a 30 will work), but this is the first time I smelled burning wires and had the sound quit.

So, I pulled the fuse and went on. Got to work, cut the switch and decided to pop the fuse back in and it sparked. Now, this concerns me because the switch was OFF and the fuse shouldn't spark with no current. I immediately yanked it and decided to tackle this later. As I walked into work, I noticed the running lights were on. Since the headlights had been turned off, I didn't know why they were on. Turns out rotating the DIMMER turned them on and off. I replaced the switch not long ago, but I made sure the wires were hooked up right and this has NEVER happened before. So, I turned them down and went inside.

Here is my fear. First, I have something hot running all the time now. Aside from the obvious fire hazard, there is the battery draining and all kinds of other issues if the dimmer isn't the only thing "hot". Second, if these weird electrical issues are cropping up, I have to assume there is a short somewhere or crossed wires or something.

So, given all of this, I am thinking my best bet is to rewire the entire thing from scratch. So, would it be in my best interest to find an aftermarket wiring kit/fuse block and go that route or try to stay with the factory fuse block and trace these wires to see where the problem is?

Any help would be appreciated.

 

Electrical issues can be daunting given all the possibilities. But, replacing the harness can be a real bear since, at least on the 82's I've had and the 85 I parted out, the main harness goes from the left hand headlight to the right hand headlight via the dash, and winds around everything in there like grapevine.

So, I would get a digital volt meter (DVM), put it in current mode, disconnect the battery's negative cable, insert the DVM with it set on the 10 amp range, and see what current is being pulled. If essentially nothing is shown you can step down to lower current ranges, but start at 10 amps.

If you have current then start pulling fuses to see what circuit the load is on, and then follow that to find out where the problem is. Many of us on here have wiring diagrams so can probably help you figure it out, but it will take time and patience.

 

I would appreciate it because I have NEVER done anything electrical before. I have a meter and I think I understand what you are talking about doing, so I can probably muddle through it.

What is really a red flag for me is the 30A fuse where there is supposed to be a 5A fuse. Tells me someone did something and this was their "fix" for blowing fuses. If it were a 7A fuse where a 5A went, I might not worry as much. When it blows everything under 30A, that tells me there is a LOT of current going through that one circuit and I am not real sure I can trace it.

Adding to this problem is this truck is now being driven a lot more. My DD died back in December and the wife and I have carpooled so we could put off getting another vehicle until we could buy one outright to avoid a car payment. I don't drive it every day, but with one kid running track at school, the other starting baseball and all we have to do, I need another vehicle and can't park this one while I fix it.

Of course, catching on fire while driving down the road would be worse than walking!

Thanks in advance for the help!

 

You should NOT run a 30 amp fuse where a 5 is supposed to go. The wires in the truck are not capable of carrying that much current. You need to pull that fuse immediately and drive without whatever doesn't work until you get that sorted.

So, what doesn't work when you pull the fuse?

 

If you smell burning wires and the headlight switch is acting funny you ought to pull the switch out of the dash and investigate both it and the plug/harness that attaches to it.

The plug is known to get hot and fail.
Sometimes the insulation burns off one or more wires and connections get 'made' that shouldn't be made...

The plug w/ pigtail is commonly found in the aftermarket.

One thing that helps is installing a headlamp relay kit (like the one from LMC Truck)
This takes a lot of current off the switch and dashboard wiring.

 

I pulled the 30A fuse and it isn't going back in until I can figure this out. I can't tell what doesn't work without it. I will trace some more when I can tear it down this weekend.

I had another thread about the dash lights going out that detailed more of the woes with this thing, but I will try to summarize. Basically, this thing is a gift from my MIL when her second husband died. She didn't want it and gave it to me. All I was told was the motor had been rebuilt once. That's it.

After I got it, I noticed when the dimmer was turned to cut on the interior lights, the radio would stop working. No biggie, I just didn't turn on the interior lights. Since this is a beat around truck, I rarely drove it and when I did, it was usually during the day. About a year later I decided to upgrade the factory radio with one I had laying around. I made sure all wiring was right, it came on fine and all was good. Until I turned on the headlights. Radio went off, dash lights went off and interior lights went off. Dimmed down to nothing, the radio would come back on, but nothing else. Then one evening while trying to figure out the radio, the dash lights quit altogether. I thought it might be the light switch/dimmer going bad, so I replaced it. Same thing. I checked the bulbs in the dash and they were fine, so I was stumped. I disconnected the radio from the power wire the old radio was hooked to and used the hot wire to the clock just to see if that would fix anything. It didn't. That's when I noticed the fuse issue. I reached to wipe some dirt off the 30A fuse and burned my finger. I KNEW that wasn't right, so I shut everything down, let it cool off and pulled the fuse. I have a Haynes manual with a wiring diagram, so I saw that was the fuse for the radio and it was supposed to be a 5A fuse. NOTHING below a 30A worked. Every one blew the second I put it in. So, (stupid, I know) I put the 30A fuse in to continue testing and got called away and forgot about it. Until today!

Anyway, not driving this much, I put it off until another day. I drove it to work rarely when needed, but it never game me problems aside from the dash lights not working. Until today when I cracked it up, smelled burning wires and remembered the fuse. I pulled it and did all as I described above.

This it turning into WAY more than I had planned for a beat around vehicle. I need to figure out what is on this circuit that was wired wrong, if there is a short somewhere or what, exactly, is going on. I can't keep driving it like this and I know with spring coming up I will need it some even if I get a DD immediately.

As for the headlight relay, how easy is that to hook up for a novice? I can fix about anything, but electrical stuff sometimes baffles me.

 

The kit is plug and play.
You need to secure a ring terminal to ground near each headlight, a power terminal to the hot lug of the fender mounted solenoid and screw down the two relays (high & low beam)

Other than that you plug the right hand headlamp socket into the harness and the harness into each headlamp.
(the drivers side socket remains unattached)

It's at the bottom of page 66.

LMC Truck Parts - Page 66

 

If you can't tell what doesn't work with the removal of the 30 amp fuse, then maybe you don't need it? Check your lights, inc tail and turn, to make sure you are safe. But, if the engine runs and the necessary things work, is it a problem that needs to be solved?

Do the test of current from the battery when everything is off - and especially with that 30 amp fuse out, as normal DVM's can handle 10 amps but not 30. If you find current then, as said, start pulling fuses until you figure out which circuit is doing it - and let us know.

I haven't done the headlight relay yet, but Jim knows what he's talking about and I'm sure you can do it.

 

For $30, I will definitely give it a shot!

Thanks!

 

The switch and plug get old and the contacts corroded.
That makes a lot of heat when the current has to pass through.
Plus, that wirewound dimmer rheostat on the back of the switch has a ceramic insulator for a reason!

No one ever opens up their dash to clean the contacts or the plug.
I've done at least four plugs so far. (none in my truck)

Putting the relays under the hood means the switch only has to provide enough current to trigger the relays.
Most of the 110/120W it takes to power the headlights doesn't have to pass through anymore.

 

Gary - I can't see anything that doesn't work without the fuse, but according to the wiring diagram in the Haynes manual, it is just for the radio. I KNOW that the factory radio never pulled 30A and I know the one I just put in doesn't either, so something else has to be on that circuit to blow fuses like that. Since I never connected the radio back up to the factory hot wire, it is still coming off the hot lead to the clock, which never worked anyway. That would explain it still working with the fuse out. Doesn't explain the sound not coming out, but I suspect that could have something to do with the "pop" this morning. I just hope I haven't fried the radio!

The ONLY thing that I can think of outside of someone not hooking something up right is that there is a wire somewhere shorting out or frayed or something that might be pulling current. It may not be pulling enough to fry everything, but enough to blow fuses up to 30A. I really don't know.

Oh, and the interior cab light (over the rear window) as well we the cargo light have NEVER worked. I don't know if those have anything to do with any of this, but I never had been able to get them to come on.

Jim - I put a new switch (Autozone) in not long ago thinking that was why the dash lights didn't work. I hooked everything up just like the old one, so I can't explain why the running lights (side of the fenders, tail lights and on the front) would be going through the dimmer and dimming when I turn it. They should come on when the light switch is pulled and the interior lights should dim. I suspect those two wires were crossed at some point, but I have no idea why I never noticed it before now.

Thanks again for all the help and I appreciate the patience with a newb trying to figure this all out!

 

In reverse order:

The interior light and cargo light work off of the switch at the end of the dashlight dimmer's travel. So, if you have a wiring problem there, and it sure seems so, then that's probably why they don't work.

I would agree that something is probably shorted, one circuit to another, so you are powering who-knows-what via the radio fuse. But, if you don't need it and aren't planning to put the truck into daily service......

Let's concentrate on one problem at a time and conquer that one and then move on.

 

Shouldn't the clock dim with the rest of the dash?
I would use the cigarette lighter for constant power to radio memory.

30A is a lot for any of the lighting wires in the harness to carry.
I'm not sure why the parking lamp circuit would be connected to the dimmer.
Parking lamps should be the first position of the switch.

If the PO was in there it's hard to tell what's been done.

 

Now you see why I am so puzzled!

I am beginning to think I need to start at the dimmer/headlight switch and work my way around. It sounds like there may be something going on in that area causing a lot of these woes. I did order a better wiring book so I will begin with that. I am also planning to get the relay outfit for the headlights, too, so maybe that will help matters as well.

Since the cargo light and overhead interior light have never worked, I may try to trace those to see if there is a short in those lines somewhere that could be causing problems. I also need to recheck the wires to the headlight switch/dimmer to make sure everything is hooked up right there.

At this point the radio is the least of my worries, so I will tackle it once I get the dash lights working again and the interior lights, running lights and everything else back where they need to be.

In my previous thread someone mentioned checking the grounds in a couple of places, so I will double check those to make sure they are OK, too.

Thanks for the help guys!

 

Good luck!