Electrical Gremlins: The Simple Approach to Fixing Them

Solving electrical gremlins...

This is something NO ONE wants to do... There is more voodoo, superstition, misinformation, and downright fear about this than almost any other aspect of building a hotrod.

It doesn't have to be so scary, though.

There is a step by step process to diagnose electrical gremlins. There are thousands of ways for electrical systems to screw up. But, there is a definite way to go about figuring them out.

Ok, let's get started...

The #1 thing you need to keep in mind when dealing with electrical gremlins is to keep it simple. Use common sense...

Basically, don't dream up wild reasons it won't work. Don't blindly start looking for things and spending money replacing parts before you look at the simple, common sense things. 90% of the time it's something simple, which means most people miss it... They're looking for some complicated reason it's not working...

You may remember reading about my old '47 Chevy I had when I was starting out... When I was wiring up some simple wiring, I had an electrical gremlin...

When I got to the taillights, they were always on bright. When I hit the brakes, they were bright. When I turned on the running lights, they were bright. When any electricity went back there, they were bright.


I had them wired right... New wires. New bulbs. New pigtails. New brake switch. Everything was new. I had the guys in my club look at the wiring... It was fine. . But it wasn't working right...

I went back through everything. I spent hours.

I finally took it to an automotive electrical place to have them look at my work. They said it should be working fine, but couldn't figure out why it wasn't.

Depressed, I was talking with dad... I told him how much time I had spent, how much money I spent, and how many people had looked at it. But the bulbs just wouldn't work right...

He said "did you check the bulbs?"

They're brand new bulbs!


So out I go to look at the bulbs. They looked fine. But I pulled a bulb anyway and stuck in another new bulb I had laying around.

They worked fine.

It turns out one of the new bulbs I had put in apparently had a short inside the housing.

If I had just thought simply and checked the first thing that didn't work, (the bulbs), I would have saved all that time and money...

90% of the time electrical gremlins are something simple.

So, where do we start?


Make sure the battery and grounds are ok.


The battery and especially the grounds are the cause of a major amount of the electrical gremlins out there.

Check your battery. Is it physically ok? No leaks or cracks? Is it fairly new? Is it strapped down properly so it can't bounce around and short to something? Is the water level up? If it's not, fill it with distilled water.

Use a voltmeter to test your battery. A healthy, properly charged 12 volt battery should read at least 13.2 volts with the car off and no electrical draw. If you don't have a voltmeter, get one and learn how to use it. It's pretty easy and they're cheap. You can also get your battery checked for free at most auto parts stores.

Now check your battery connections. Are they corroded? That's a big reason for electrical gremlins. Clean them and put some stuff on them to keep them from corroding. I like to use the chemically treated felt washers you put under the connections.

How are the battery cables? If they are green around the ends, swelled up under the insulation, or the insulation is discolored, replace them. These can cause lots of resistance in your electrical system and intermitten problems.

Now the biggie... GROUNDS

Bad grounds are probably the biggest cause of electrical gremlins there are. Especially in older cars. No one ever checks them. The connections get loose, get corrosion or rust under them, and sometimes even rust off.

Clean all your ground connections if you have an old car or your hotrod is subject to harsh environments (like four wheeling or winter driving).

Remember, you can never have too many grounds. If in doubt, add some more grounds.

Example: First generation Camaros often have a problem with the gauge cluster losing ground after being taken out and put back in causing all kinds of problems. Putting a ground wire from it to the metal dash fixes it.


What's your problem?

Recognize what the problem is. Remember common sense... Will it not start? Battery going dead? Something not working? Fuse blowing?

Ok, now that we know what the problem is, let's start looking for causes.


Start with the simplest thing it could be.

-Starting problems

Do you here a click when you turn the key, but it doesn't turn over? Were the battery and the battery cables ok? Working the cables at the connections gets many cars started because they were dirty or loose.

Do you hear a high pitched whirrrr from the starter when you turn the key? Does it do nothing at all? Try hitting the starter with a hammer if you can reach it or with something solid. Often this will get a starter working at least once more. Your starter is probably going out.

Do the dash lights go dim when you turn the key but the starter doesn't try? Do you know if the engine can physically turn over? Is there something binding it up? Sometimes it may not even be electrical. Something may have broke and is not letting the motor physically turn.

Does nothing happen at all, but the lights and everything else seem normal? Then you probably have a break in the starting circuit. Try to jump the starting relay or starter solenoid with a remote starter switch (best), a jumper wire (not as good), or an (old) screwdriver (last ditch effort). If it tries to start, then you probably have a bad wire to the unit or a bad ignition switch.

If it won't work then make sure everything is in place for it to start. Is the automatic shifter it place or the clutch pedal pushed down? Sometimes the neutral safety switch may be loose or bad. Try jumping that before you start replacing parts. If wiggling it or jumping it works, there's your problem.

-Charging problems

First, look at the alternator. (Common sense) Is the belt still on? Don't laugh, some people miss it... Does it have a broken bolt? Sometimes something will have broken loosening the alternator even though it still looks ok and the belt's still on.

Is the belt ok? If it's old or loose it may not be spinning the alternator fast enough. It could be slipping even though it's not squealing. Tighten or replace if old or bad.

Now check connections. Often the connections at the alternator or voltage regulator if so equipped may be corroded or bad. Don't just start spending money on an alternator, battery, or voltage regulator. It may just be a bad connection.

Now check the voltage output of the alternator at the battery. Use your voltmeter. It should read 14 to 14.5 volts with the engine running. Most auto parts stores will check it for free also...

There are lots of tricks guys use to see if the alternator is bad. However, they often don't work because the alternator doesn't always just go bad. Often, the alternator will be charging, but not fully. This can lead to frustration because now you think it's not the alternator, and you start another wild goose chase. Check for proper voltage.

-Something electrical doesn't work

First, the part may be bad. But don't start spending money just yet...

Make sure it's getting power. Are the connections dirty? Disconnect it and see if you have power coming to it with a test light.

If you have no power coming to the component, then you must trace the wiring back through the circuit to find out where the break is. It will likely be a fuse or a switch, or a faulty connection somewhere.

If you do have power then see if it's grounded well. The unit will either have a ground wire or be grounded through its casing.

Hook a test light from the hot wire going to the component to either the ground wire, or the surface where the component was grounded. If the light works, the ground is good. If you have power and ground, the unit is probably bad.

However, you also need to make sure the unit is making good contact if the unit grounds to the mounting surface.

I once saw a truck that was blowing HEI modules in it's distributor. No one could figure it out and knew it must be an electrical gremlin in the wiring.

It ended up the distributor body wasn't making good contact with the motor, which is how it grounds. Rust and corrosion had built up on the distributor hold-down, making a bad connection. The added resistance was blowing the modules. Something simple.

-Short circuits

Shorts can be very aggravating, but common sense will usually figure them out.

Usually the problem will show itself in either blowing a fuse, draining a battery, or making sparks and smoke. The last one is usually easy to find...

If a component only works intermittenly you have at least figured out the affected circuit.

If you're blowing a fuse, that will narrow down the circuit to what the fuse controls, usually. Start at the component and work along the connections, wiring, switches, etc. looking for damage, wire insulation worn away, cut, or melted, etc.

Most damage is caused by vibration or something hitting it in factory harnesses. However custom wiring not properly supported by wire ties, grommets, etc. can experience alot more damage.

If your battery is draining, you have a short that is not enough to blow a fuse. First make sure everything is off in the car. You may have to disconnect the light under the hood if you have one. Now disconnect the positive cable from your battery.

Now touch a test light or a voltmeter between the positive cable end and the positive battery terminal. If there's a power draw, it will show up in the voltmeter or light up a test light. If it's a small draw, the light will be dim. If it's a big draw the light will be bright.

Now you know you have a short. You also know approximately what size it is, narrowing down the circuits it could be.

Now see which of those circuits don't work. That will often tell you what it is.

If all the circuits seem to work, have someone pull the fuses one at a time. (Remember to have the door shut or pull the courtesy light bulb.) Now see when the voltage goes to zero or the test light goes out. When it does, that fuse indicates what circuit(s) are causing the problem. Now you can look for problems along that circuit...

To wrap up...

Electricity can do all kinds of weird things when something disrupts it. It will follow a path of least resistance somewhere. That's what freaks people out.

However, now that you know some tips and tricks and the order to do things, you can figure some of this stuff out.

Remember, to find and fix electrical gremlins, keep it simple and use common sense...

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