Attacking the Rat's Nest

[Chris]

Took the 55 out the other night only to find I didn't have dash lights. After getting home found I didn't have tail lights either. Blown fuse explains it but when popping a new one in I can watch it glow then blow.

The PO added trailer hitch wiring and a manual switch for backup lights and about a pound of house wiring wire nuts and electrical tape. Pulled all of it yesterday and will reconnect the original wires when it warms up a bit. Hope that takes care of it, if not I have to dive under the dash and start checking things out.

I hate wiring! :rant:

[Funrover]

Oh man this sounds familiar.... I have a 65 dodge that was a wiring PITA.... have fun

[Chris]

I'm not looking forward to this. Having a 69 body on a 77 frame with a sbc makes wiring diagrams kind of useless.

[Funrover]

Have you ever thought of having a new one made? painless wiring is a pretty good company for those kinds of things

[Chris]

Yes, I have but can't really afford it. I found the problem isn't the rat's nest but my electrical troubleshooting skills are seriously lacking. Anyone here good at it?

[Patrolman]

Not gonna say that I am an "expert" but I did ace Electronics and Automotive electrical at the CC before going to get my BA. I can use most any function on a multi-meter. Can try to walk you through some things. First things first I would take out any EXTRA wiring like the towing lights. Make sure that you are down to the basic wiring harness. Sounds like you are on that road already.

First off, the fuse lights up before it blows? Do the lights come on? If so, look for the one that DOES NOT come on. It is the likely culprit. Somewhere there is a wire that isn't making its way to the light and is grounding out. This usually isn't in the dash but usually at a parking light. They just get more wear/tear. Since the parking and dash lights are tied together on the fuse panel they will obviously go out together.

If the lights are not coming on at all, then what I would do is start with 1 light. Take it apart, inspect the lighting. Make sure that there are no obvious signs of shorts (or shirts).

If a visual does not turn up anything, then time to take out the multimeter and go at it. Will leave that till later since that gets more detailed. Let me know how it turns out!

[Chris]

Not gonna say that I am an "expert" but I did ace Electronics and Automotive electrical at the CC before going to get my BA. I can use most any function on a multi-meter. Can try to walk you through some things. First things first I would take out any EXTRA wiring like the towing lights. Make sure that you are down to the basic wiring harness. Sounds like you are on that road already.

I've taken out the rats nest (trailer wiring and switch wired to turn the backup lights on. Hoped that was it. Extra wiring! I have a number of wires hanging along with a bunch of connectors that don't go anywhere.


First off, the fuse lights up before it blows? Do the lights come on? If so, look for the one that DOES NOT come on. It is the likely culprit. Somewhere there is a wire that isn't making its way to the light and is grounding out. This usually isn't in the dash but usually at a parking light. They just get more wear/tear. Since the parking and dash lights are tied together on the fuse panel they will obviously go out together.

It's just the tail lights and dash lights which are on the same fuse. I turn the lights on, watch the fuse light up and blow. I guess I should pull the lights as you suggest and check them out. The problem there is I think it includes the license plate light which is far gone and a good suspect. The bad thing is it looks like I have to dismantle the whole thing to get at the light.


If the lights are not coming on at all, then what I would do is start with 1 light. Take it apart, inspect the lighting. Make sure that there are no obvious signs of shorts (or shirts).

They used to work. :(


If a visual does not turn up anything, then time to take out the multimeter and go at it. Will leave that till later since that gets more detailed. Let me know how it turns out!

Multimeters baffle me. I hope I don't have to go that far. Thanks for the tips, any way to check the license plate light to see if that's the problem w/o accessing the backside?

[Patrolman]

Not really any way to check a light to see if it is a problem without tearing into it or using a multimeter. Guess it is time to learn how to use a multimeter? Maybe when the weather warms some we can tackle it.

[Chris]

Yeah, I have a couple but that's as far as I've gotten. I'll figure it out eventually, until then I'll be home by dark. :lol:

Maybe I'll call on you to help ;)

[Brody]

Here is my 2 cents.

A cheap multi meter works great. You can get one at Radio Shack or Depo for around $12 that will do more than you want to know about. I piggy back wired a couple of alligator clips to my + and - lines so that it was easier to use. That way I could just ground one and then probe. I also sharpened the ends of the probes so that I could poke through the insulation on the wiring easier. Using a utility razor blade to do the same works, too, and then you just clip the probe to it. What is also very handy is just a $3 idiot light tester with just a ground and a probe.

If you are working by yourself testing this stuff, buy a small LED light for a couple of bucks and wire it to a couple of alligator clips and some long chunks of wire. That way you can set the LED light up where you can see it as you are messing around on the other end of the rig. A scrap horn works for this, too, but might irritate the neighbors...

A couple of things that are great to have for car wiring besides the multi meter and a cheap probe are a spray can of the electronics parts cleaner, some dielectric grease and some liquid electrical tape. I use dielectric grease on everything electronic-fuses, crimp connectors(hate 'em), battery terminals, etc. Liquid tape is great for when you shave the insulation off the wires to test them and need to cover them back up.

You also might want to consider making some additional grounds to your chassis and motor/chassis/battery connections. I would start with the original ground connections first and just make sure that they are clean and the wires are good. Then I would add an extra chassis to body ground somewhere and maybe an additional battery to body/chassis ground. If you know that your rig really well grounded before you start fooling around with the other stuff, you have just eliminated about 2/3s of your headaches as most auto electrical problems stem from a bad ground.

[Patrolman]

Brody made a LOT of great points about stuff. Don't waste $ on an expensive multimeter. I think mine were $3 or so on sale at HF and they fit in the glove box. Do WAY more than most people know how.

Grounds are common problems for items that don't work. The way I attack problems is basically in 2 categories. If something isn't working at all but the fuse is good, then it is usually either no power or a bad ground. This is an "open" as the circuit isn't being completed. Those are super easy to check. If the fuse keeps blowing then there is a "short" where the power is going back to ground before it reaches the item it is supposed to power. It basically makes the electrical loop shorter hence the name. Based on your symtoms, you have a short.

If you can't get it figured out this weekend, I should be able to find time next week to swing on by and help out. We can also try to knock out the front pinion seal.

[Chris]

Yeah, it's a short. It occurs to me that since it's probably in the tail light area I should be able to disconnect the harness in the cargo area that feeds the rear and put in a fuse to see if it blows. If it does the short is before that, if not the short is after that connection, right?

Yeah, I'm not good at this...

[Chris]

Continuing my theory I did what I mentioned above and the fuse blew. I then disconnected the same harness front connector and put a fuse in that didn't blow so I'm deducing the short is in that chunk of harness.

Edit: My reasoning is false. All it actually proves is that the short is either in the harness section or after it. :o

I pulled the section of the harness and couldn't find a short but the wires were brittle and cracking so I made a new one retaining just the connectors. Onward to the individual components, i.e., the light themselves.

Sharing my experience. Exposing my lack of real understanding. :lol:

[Chris]

:woot: :woot: :woot:

I found it! I think. The PO had done some wiring for reasons I won't try to figure out and I suspected that was the problem from the beginning which is why I removed the rat's best of trailer wiring. It wasn't there. I made a new harness from the front to the back after discovering how brittle it was, that wasn't it. I isolated the rear circuits, that wasn't it. That eliminated everything.

I then recalled some soldered wires on the harness connections which I re-used and decided that was worth a new look. I consulted my wiring diagram which didn't show his setup so I disconnected two leaving the hot intact. Sure enough the PO soldered wires creating the short. I now have tail light, turn signals and I'm assuming brake lights since they're on the turn signal circuit. No license plate light because the housing nearly fell off and I removed it.

So far, so good. A bit more checking then I have to button it up and move on. It's been a learning experience that I hope not to repeat.

:cheers:

[Chris]

Checked a bit more and still didn't have brake lights but I do now! I'm almost done now, just need to wrap up the details which pleases me a whole lot!

[Patrolman]

Glad that you got it figured out! It is always the last place you look, right!? I think the most frustrating thing about wiring is that it takes a lot of "tracking" to find 1 tiny little problem. It isn't obvious usually and takes going through a lot of good wiring to find the issue. At least with brakes or something else it is usually visually obvious and the end result is pretty clear from the beginning.

[Chris]

Thanks, I still hate wiring. :)

Yeah, pretty much the last place I expected it to be. Still need to do the Corona license plate light to replace the rusted original but that's easy. When it gets dark enough I'll see if I have dash light. I hope, I hop, I hope...

[Chris]

No dash lights. When testing I noticed the headlight switch was quite hot only to flip it over and see it was glowing red. :eek:

It appears to be an old rheostat, loops of wire with a connector that slides over it when turning the knob. I turned it away from the glowing connection but suspect I found the dash light problem. :(

I'm not thrilled with the prospect of trying to find another one suspect that's what I'll have to do unless there's an electrical wizard here that tells me I can just wire around the fried section.

[Brody]

Chris

I forgot to add: "put in an auxilary fuse box" with my electrical (don't know where it went) post for your stuff. Sometimes it is easier to just reroute stuff to a new box rather than trying to find a short.

[Chris]

Moved it for you ;)

It's on my list, rather long list but it's on it.