How to increase your odds for success at automotive wiring, electrical installation and trouble shooting.

[WP29P4A]

I thought I could make this an ongoing thread with useful tips I have learned over the years, to share with you guys as long as the thread didn't get sidetracked with random discussions. Looks like you guys have got this handled so I'll go back to teaching myself how to touch up metalic paint with an air brush.

 

[Matt69olds]

The best advice I can offer is to buy a FACTORY service manual for any GM car from about model year 85 to the early 90s. Things like charging systems, power windows, door locks change very little from the early 70s to the mid 90s. The nice thing with GM is they tend to keep the same wire colors. For example, Brown was the color for the taillight power feed on the early 60s, and the same color today.

Another nice thing about GM manuals is they describe how a circuit is supposed to work. It’s much easier to figure out why something doesn’t work, when you understand HOW it’s supposed to work.

The next best advice: throw away the cheap crimp butt connects. Learn how to solder a wire correctly. Buy good quality electrical tape, environmentally sealed heat shrink, and quality terminals and connector bodys. Invest in a good test light, and good crimpers.

These trucks were pretty reliable when new. Most of the electrical problems are caused by half assed repairs and custom additions.

 

[GTX63]

In the 80s and 90s, I made assumptions because the trucks were mostly unmolested and in original condition. Now, in 2023, a 45 year old truck that has had 13 owners, 7 different stereos, CBs, equalizers/boosters, aftermarket lighting and guages, alarms, batteries, starters, alternators new and used and all installed by anyone with access to a tool box, I test and confirm.

 

[Redfish]

I agree with almost everything you guys have said here but I will say that not everyone starts at the same point in a troubleshooting job. Some begin at the power source, some at the end user and others like to find a point somewhere in the middle and work from there.

One of the best electrical troubleshooters I ever worked with always began the conversation with, "Did you check for power?" It didn't matter that he and I had been working together for years, it didn't matter that we had never failed, he was always going to ask that question and we were NOT going any farther with the process until that question was answered. Methodical=Successful.

Another thing I will add is that having decent, accurate, and reliable Test Equipment is very beneficial. Knowing how to use it...Priceless.

I make most of my wife's money in a small ethylene refinery, I troubleshoot everything from the millivoltage signal generated by a thermocouple all the way to 13,800 Volts. I frequently find myself chasing electrical gremlins in someone's classic vehicle. It's always better if I have drawings but sometimes I just have to figure it out.

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[Doppleganger]

"I make most of my wife's money...."

LMAO

I'm the same way only with grounds. I think 3/4 of every issue I have ever had stemmed from bad or missing grounds.

 

[GTX63]

I had a guy stop by that owns a 73 C10. No headlights, no tail lights, no dashlights.
He has the headlight switch pulled out, the tail light lenses off, he has 194 bulbs from the dash laying on the front seat, he has been under the truck pulling wires from the loom and all he can say is "There is no power anywhere!"
Ok, no assumption, we know there is power at the battery. He didn't know that the circuit for the lights begins at the starter solenoid. Yes, it is hot there. So following that wire, the next stop was the junction block on the firewall between the distributor and the master cylinder. Big red wire with a fusible link. The connecter was broken off and the wire was hanging down behind the distributor. It took us all of about 4 minutes.
Of course, not every troubleshoot goes like that; most of the time I am cork screwed under a dash or scratching my cornea with falling rust. But that was just a small example of starting from the origin and working from there.

 

[SirRobyn0]

I thought I had posted in this thread but see I did not. At the shop I do not turn a wrench near as much as I use to due to my high mileage body leaving parts behind lol. But I always get drawn in for problems the other mechanics can't figure out. With electrical especially on old rigs, that often sit outside, some aren't driven very often, and some don't seal well in the cab. #1 Check grounds. Seems like often the guys will have done some troubleshooting, ask for my help and then I find out no one has checked the grounds....

Like Matt said throw away the crimp connectors and learn to solder. Seal all wire connections with shrink wrap. If for some reason you can't shrink wrap it multiple coats of liquid electrical tape will work. There is to much risk for water intrusion with regular electrical tape. If for some reason you need to make a connection where you can't solder you can get high quality crimp connectors without the plastic insulator on it. That way you crimp it and shrink wrap it. IMO (keep in mind also I live in the PNW so we get a fair bit of rain and moisture) the biggest issue is moisture getting into connections and breaking it down.

Next dielectric grease. Yes, I know it's expensive, but it's a big headache saver down the road. All connections that can't be permanently joined and shrink wrapped should get a coating of dielectric grease. All bulb sockets should get loaded up with the stuff too.

 

[MikeB]

How about small gauge wires that have been bent and tugged on many times over 40-50 years? I found one where the wire strands were broken, but the insulation was OK. It was a coolant temp sender wire that was hanging on by a strand or two. No wonder resistance was high and the gauge read low.

Had another one that looked OK from the top, but the insulation had been partially worn off on the bottom causing an intermittent short to ground.

By the way, these are good reasons to use automotive wire with cross-linked insulation, and not the "hook-up" wire that parts stores sell. Google it.

 

[SirRobyn0]

How about small gauge wires that have been bent and tugged on many times over 40-50 years? I found one where the wire strands were broken, but the insulation was OK. It was a coolant temp sender wire that was hanging on by a strand or two. No wonder resistance was high and the gauge read low.

Had another one that looked OK from the top, but the insulation had been partially worn off on the bottom causing an intermittent short to ground.

By the way, these are good reasons to use automotive wire with cross-linked insulation, and not the "hook-up" wire that parts stores sell. Google it.

To be quite honest with you we see the broken wire insulation ok thing at least a few times a year at shop. Almost always it's in the door where wiring articulates or at the truck or rear deck lid where wiring articulates. The only way to find it is a failed continuity test followed by knowing this can happen and running your finger nail along the wire to feel the internal break. Obviously this applies to all makes and models and is not square specific.

 

[Camar068]

To be quite honest with you we see the broken wire insulation ok thing at least a few times a year at shop. Almost always it's in the door where wiring articulates or at the truck or rear deck lid where wiring articulates. The only way to find it is a failed continuity test followed by knowing this can happen and running your finger nail along the wire to feel the internal break. Obviously this applies to all makes and models and is not square specific.

we have to do this at work on medical equipment all the time. Put the meter on it (be it ohm or voltage) and start moving wires around. If it's wiring, and you move around every length....you'll find it. Normally quicker than you think.

A good set of 6-8' test lead extenders (wire with gator clips on each end) works wonders as well. As with all test leads and extenders.....test them, before troubleshooting, with an ohm meter (otherwise you could be chasing your tail because of a bad lead to you meter). I found a few this weekend I need to repair. Test them every time before you start troubleshooting.

And during troubleshooting with a meter, if you start getting readings that don't make sense.....check your leads/extensions again to make sure.

 

[SirRobyn0]

we have to do this at work on medical equipment all the time. Put the meter on it (be it ohm or voltage) and start moving wires around. If it's wiring, and you move around every length....you'll find it. Normally quicker than you think.

A good set of 6-8' test lead extenders (wire with gator clips on each end) works wonders as well. As with all test leads and extenders.....test them, before troubleshooting, with an ohm meter (otherwise you could be chasing your tail because of a bad lead to you meter). I found a few this weekend I need to repair. Test them every time before you start troubleshooting.

And during troubleshooting with a meter, if you start getting readings that don't make sense.....check your leads/extensions again to make sure.

Right, I think with the thing you said about finding it quicker than you think, I think knowing what to look for / time and experience really makes locating those issues a lot easier.