I don't post much at all, mainly because my old girl used to be a beat around, use every once in a while truck. Recently, however, I have been driving it a lot more due to my DD dying after 15 wonderful years.

Anyway, I have a weird electrical issue that I noticed when I put in a new aftermarket radio. A little history:

First, this is an '84 F150, 351 HO with a frankensteined carb and 4x4. Before I ever did ANYTHING, it had some weird issues with the dash lights, interior lights and headlights. I could turn on the headlights fine, but adjusting the dash lights or turning on the interior lights would cause them to turn off. I assumed it was a bad switch, but since I rarely drove it, this wasn't a high priority issue.

Last fall I added a new radio I had laying around and the problem was worse. I figured the ground to the original radio was bad, so after redoing it, nothing got better. I played with it and played with it, until I finally ran a new wire from the battery back to the radio for the constant lights and capped off the line I had been using from the factory radio. Interior lights still gave me problems, only worse. One night they finally wouldn't come on again. I figured a blown fuse.

Here's where it gets weird. First, the fuse for the radio/interior lights, etc. was a 30 amp fuse. According to the book I have, it is supposed to be a 5 amp fuse. I put a 5 in it and it blew immediately. Same for every size up to a 30, which is what it had in there originally. I KNOW this is not right, so someone, somewhere wired something up wrong and this was the "fix". So, next I replaced the light switch. Still no dash lights. And turning it to turn on the interior lights flips the radio off, from drawing too many amps. Turn it back, the radio comes back on.

Assuming I may have fried some dash lights, I pulled it and NONE are blown. I switched them out just to make sure and nothing. Turn signal lights work, interior lights work, etc. Well, interior lights on the side walls work, but the rear cab lights above the rear window have never worked. Again, not high priority.

Apparently something somewhere was screwed up at some point and the jackleg who worked on it "solved" the problem by putting in a fuse that would handle it. I was told the engine was rebuilt once, which is probably when they pieced together the carb, but it works, so I will tackle that later. For now, though, I have NO dash lights and every time I move the lights switch, something cuts off. Oh, and I never had figured out the cargo light. Never has worked and I can't figure out where or if there is a switch for it to even test.

So, is there a good place to start tracing this mess? I need dash lights, so if there is another fuse, regulator or something else that may have blown can someone point me to the right place to start? Also, I would LOVE to get the wires down to just a plain old standard engine the way they used to do it. Tail lights work, head lights work and I don't see me messing with that unless I have to, but at this point I wonder if I wouldn't be better off pulling everything and getting an aftermarket wiring kit and starting over. Doing that scares the crap out of me, though.

Also, I noticed the blower motor sometimes doesn't come on until it has been running for a minute or two. It is almost like it is having to build up amps to get things going. I have also put in 3-4 starter solenoids since I have inherited this thing, which I thought was unusual. Alternator is "new", but I wonder if it is the wrong one for this vehicle. I am really at a loss, so any help is appreciated.

 

I'm guessing you have a ground problem. GUESSING. But, ground problems cause weird issues that aren't easily explained - like yours. IIRC, there is a large ground up under the dash for most things, and it may be above the brake pedal. However, if the engine was rebuilt I'd bet the ground from the engine at the back of the block on the driver's side wasn't installed. It goes from the back intake manifold bolt to the firewall.

Another ground that is often overlooked is the one on the ground cable from the battery to the block to the frame.

A way to test the theory is to connect a volt meter to the battery ground with the negative lead and put the positive lead to something like the radio's case. Then start turning things on and off and see what happens to the volt meter's reading.

 

One question is why would the dash lights stop working completely, though? I didn't do anything to them after the radio install and they worked for a while, just all of a sudden stopped working. Could I have blown something somewhere or maybe the ground somewhere wasn't quite right and this pushed it over the edge?

The ground under the dash, does it run anywhere near the radio? I wonder if I could have pulled it loose or something.

Just curious if there is something else I need to look for as well. I'll start checking those things you suggested and hopefully that will fix some of this mess.

Thanks for the help getting started!

 

You may have more than one problem as I don't know why the dash lights would stop working. But, again, bad grounds do strange things that are difficult to explain. So, I would check the engine-to-body ground at the firewall and the battery/block/frame ground via the negative cable. If they are good, and that means you've taken them off to ensure clean metal under all connections, then we'll look elsewhere.

As for the dash ground, I believe it goes to the pedal "cage" and terminates in a ring-tongued connector under a bolt. IOW, it isn't likely you knocked it off or loose. And, unless someone has been doing things they really shouldn't that wire is probably still there.

 

The light blue/red-stripe wire is the dimmable dash lighting circuit. If you hooked up your radio wrong and grounded that wire somehow, bad things will happen.

The factory radios are grounded through the case & antenna connection, and I don't think I've seen an aftermarket radio that has accommodations for dimmable backlighting (or any externally-supplied backlighting for that matter).

 

Good point, Chris. If the radio's lighting is hooked to that it could kill the lights since the rheostat is old. Having said that, if it is turned to full the lights might work.

 

Some aftermarket radio's do provide for that, My Pioneers and the one JVC all allow for dimming. It's a single stage, but it still dimms. The JVC has two inputs depending on they type of system in the vehicle whether resistance to positve or ground. My Pioneer only has a positive input.

 

If problems began after installing the radio, remove it and put it back how it was and see if your problems leave with the change.

You list all kinds of problems with different circuits, I suggest getting yourself a factory wiring diagram manual (HERE is a used for $40) and maybe an EVTM (electrical/vacuum troubleshooting manual) those books combined with a multimeter will help you TREMENDOUSLY.

The blower thing, try jiggling the key back towards yourself and see if that helps, the mechanisms get gummed up and don't always spring all the way to RUN from START.

 

OK, I REALLY appreciate the help here and I realize I haven't been very clear on most of this.

The dimmer issues have always been there since I got this ride. Turn on the interior lights on the dimmer switch and the dash lights would go off/flicker, but they WOULD adjust as you would expect them to. Just when you turned on the interior lights, things went nuts.

The radio is a Pioneer and has a separate line for the dimming of the front. The blue/red stripe wire *may* have been used for this, I just don't remember, but that is easy enough to check. I will do so very soon. I think this may have been the reason for the current issues, which include the radio and everything (including the blower) shutting off when you turn on the interior lights. My biggest problem now is I can't get the dash lights to come back on. I will try playing with the wires in and around the radio and see what happens.

Thanks again!