1979 Chevrolet El Camino reversed battery cables

Tiny
MOTOPSYCHO
  • MEMBER
  • 1979 CHEVROLET EL CAMINO
  • 5.7L
  • V8
  • AUTOMATIC
On my 79 El Camino, while re-installing the battery, the cables were connected backwards. They touched for a mere second, then once it was realized, they were removed. The vehicle will not start now. I have replaced all fuses in the fuse box, as well a 20 amp circuit breaker. (Not quite sure if the circuit breaker is in the right place however). The headlights, rear lights, power windows and interior lights work. The instrument panel lights and the keyless entries do not. When the key is turned, there is no power to turn the engine. It is as if there was no battery connected, keeping in mind the headlights, rear lights and power windows do. I was told there could be a fusible link that was affected. How and where would I find the fusible link? I have replaced the fuses in the inline wiring. Or perhaps you may help me with other alternatives to check so that I can get power to the ignition to start up my car. Please feel free to ask any questions that will help in the remedy of my problem. Thank you
Do you
have the same problem?
Yes
No
Saturday, November 29th, 2014 AT 7:52 PM

4 Replies

Tiny
CARADIODOC
  • EXPERT
GM commonly used the larger battery terminal on the starter solenoid as a convenient tie point for other circuits to tap off of, and that's where you'll find one to three fuse links. Tug on those wires. If they're okay, they'll act like a wire. If they're burned open, they'll act like a rubber band.

The advantage to using fuse link wires is they take a while to burn open. It takes considerably more than a momentary short or reversing the battery polarity. The biggest thing you have to look at on a '79 model is the generator. They have six diodes which are one-way valves for electrical current. When the battery is connected correctly, those diodes are in the circuit backward. That's what prevents the battery from discharging through the generator when the engine is off. With the battery polarity reversed, those diodes are "forward biased" meaning they're turned on and act like a dead short. While a fuse link protecting that circuit also would take some time to burn open, some of the diodes can short instantly from the excessive current of a reversed battery. Once they're shorted, they're shorted permanently and will act like a piece of wire. THAT'S what will burn that fuse link open when the battery is connected correctly. It's not practical to replace the diodes. While it can be done fairly easily on that older style generator, the parts will cost just as much as a rebuilt generator with a warranty.

To test for this, measure the voltage on the large output stud on the back of the generator. If you find full battery voltage there, the fuse link and generator are okay. If you find 0 volts, replace the generator, then look for the fuse link in that fat wire that goes back to the battery positive terminal. I would expect to find additional wires bolted to that stud in that case too, and that would explain why some circuits are dead.
Was this
answer
helpful?
Yes
No
Saturday, November 29th, 2014 AT 9:00 PM
Tiny
MOTOPSYCHO
  • MEMBER
Thank you for your advise and answer to my question. I really appreciate your help. I do have a couple more questions. I do not have a generator, I have an alternator. Do I consider it to be a generator, and proceed with your advise? Also, what does a fusible link look like? I am hoping to hear back from you this evening, as I plan on working on my car tomorrow with hopes of getting it up and running. Thank you again for your help
Was this
answer
helpful?
Yes
No
Saturday, November 29th, 2014 AT 9:20 PM
Tiny
CARADIODOC
  • EXPERT
You're only the third person to note the "alternator" story. In an effort to use correct terminology with my students, it must be noted that Chrysler developed the "AC generator" for use in 1960 models and copyrighted the term "alternator". GM and Ford followed with their versions three to four years later. While everyone will know what you mean when you ask for an alternator, the industry-standard term now is "AC generator", or just "generator". That's the term you'll find in service manuals too.

The Chrysler charging systems switched from a mechanical voltage regulator to an electronic one in 1970. Both the older and newer systems were real easy to diagnose and repair and were the best system there was. In my opinion, GM's version with the built-in regulator, like you have, was the world's second best design. They didn't cause a lot of problems, and those that did develop were pretty easy to diagnose and fix. One thing you have to watch out for though is to mark the two case halves so you can put it back together the same way. They can be reassembled four ways, and three were used depending on the application. If you can't find the right application in stock, you can use a similar one by removing the four case bolts and swiveling the rear half as needed. Just don't pull the case away because that will allow the brushes to pop out of their holder. Reinstalling them isn't hard but if you've never done it, you'll want to ask how to do it first instead of breaking them.

Your design was used through 1986. For '87, GM came out with redesigned starters and generators and they really screwed up the generators. Those are the world's biggest pile and they haven't done anything to make them better.

A fuse link, or fuse link wire, looks like any other wire but it will be a short piece of a different color that's spliced in. Typically they're less than six inches long, and they'll have a dull finish, not the normal shiny insulation most wires have. The wire is exactly the same as any other wire, but it will be a smaller diameter than the wire it protects, making it the weak link in the chain, so to speak. The major difference is the insulation will not melt or burn.

You can buy replacement fuse link wire at any auto parts store. They go by color which denotes its current rating, just like with regular fuses. Typically you'll get a piece about 12" long which is enough for two or three repairs. You can also repair the old link by cutting away the insulation until you find the ends of the wires, then you can splice and solder them together and seal it with heat-shrink tubing. As long as some of the original wire remains, the circuit will still be protected.

One other point that is worth mentioning is fuse link wires have been responsible for confusing a lot of people experienced in electrical diagnosis. When the wire burns away, the arcing leaves a carbon track behind inside the insulation just like what can develop inside a distributor cap. That carbon track can't conduct enough current to do anything, including run a test light, but if everything down the line is disconnected, the little tickle of current that can get though will be picked up by a digital voltmeter and incorrectly show that voltage is there and the link must be okay. This is a perfect example of where the cheap test light is more accurate than any voltmeter. This would be similar to where a closed valve in a compressed air line won't let enough air through to run an air tool, but if there's just a tiny pinhole leak, eventually enough air will sneak through to register on a pressure gauge. No air goes THROUGH a gauge, just like almost no current goes THROUGH a voltmeter.

Most of the fuse links GM used by the starter solenoid were gray or black. Other common colors are dark green, orange, and white. I don't recall ever seeing a red or blue fuse link. If you want to see exactly what they look like, look on any front-wheel-drive Chrysler car from the late '80s to early '90s in a salvage yard. There will be a whole pile of them tie-strapped together, going around the left strut tower. They come out of a black plastic triangular block where they're spliced to the fat feed wire, usually red.
Was this
answer
helpful?
Yes
No
Saturday, November 29th, 2014 AT 10:58 PM
Tiny
MOTOPSYCHO
  • MEMBER
Thank you for your time and professional advice. I respect and value your knowledge; I am more confident now in repairing my El Camino.
I will keep you posted.
Was this
answer
helpful?
Yes
No
Sunday, November 30th, 2014 AT 11:07 PM

Please login or register to post a reply.

Recommended Guides