Reversed Wiring - Things to check?

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mammlouk

mammlouk

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I just picked up my 1965 Dart Wagon this weekend and drove it home to Colorado from Connecticut.

I pulled the battery out to get it charged, but go impatient. I connected up a spare battery. smoke started coming from a panel with connectors that goes from the engine bay to the interior behind the dash. I disconnected it immediately. After sitting there dumbfounded for a minute I realized that somebody ran a red wire for the ground to the engine block. Since I was dumb enough to not verify the red wire was positive... I got smoke. I reconnected the battery correctly and everything seems okay so far, power rear window, lights, horn, radio, starter cranks. Is there anything particular that I should be concerned about or checking for?
 
You are LUCKY. Look at the harness where the main alternator wire goes around to the bulkhead, etc. Look and feel the harness for "meltage." The big danger is that hot wires, melt the plastic insulation, and "short" (cross connect) the wiring IN the harness. In other words you can two or more wires melted. welded to gether. "You may be lucky." If the radio works, you are probably OK.

"The big short" that happens when you hook this up with the key "off" is the alternator diodes. If it does not seem to charge correctly, you will probably have to replace it. So long as everything is OFF you are probably OK.

The other danger is solid state stuff like the radio. Again "if it was off" (and the key off?) You are OK. HOWEVER many modern stereos leave the PA transistor devices permanently across the power buss. If you have an aftermarket stereo or "amp" that could be a problem.
 
If the alternator was hooked up, the diodes were forward biased as a short circuit. The current could be high enough to fail them. Other solid-state devices as radio, electronic ignition, or regulator may also be damaged. The fusible link, may have made the smoke and is likely compromised.

I was delayed in post, so did not see Del's similar post.
 
Great replies. Exactly the sort of info I was looking for. I'm familiar with consumer electronics and minor circuit repairs, but actual automotive wiring beyond stereos, keyless remotes, etc. is a bit new to me.

Is it possible to test the alternator diodes in place with a multimeter?

Kit - As I mentioned the radio and ignition seem to be fine. Obviously initial testing may not fully uncover any partial damage. I noticed some labeling about the fusible link. A quick inspection and everything looks okay, but I will try to get a better look at it tomorrow.

I was so mad yesterday when I realized what happened. My wife said not to blame myself if the wires were color coded backwards, but I still felt like an idiot for not doing a quick check before connecting it up.
 
The best way to check alternator is to do a leakage test by placing a bulb in series with battery cable. With all electrical devices off, the light should be off. If that is good, remove bulb and start car, check battery voltage. It should be around 14V. Then put the meter on AC volts, the reading should be below 0.25V.

About the battery cables, the battery terminals have large and small ends. If you find yourself refitting those, the polarity might be being reversed. Something to keep in mind on a hookup.
 
mammlouk said:
Great replies. Exactly the sort of info I was looking for. I'm familiar with consumer electronics and minor circuit repairs, but actual automotive wiring beyond stereos, keyless remotes, etc. is a bit new to me.

Is it possible to test the alternator diodes in place with a multimeter?

Kit - As I mentioned the radio and ignition seem to be fine. Obviously initial testing may not fully uncover any partial damage. I noticed some labeling about the fusible link. A quick inspection and everything looks okay, but I will try to get a better look at it tomorrow.

I was so mad yesterday when I realized what happened. My wife said not to blame myself if the wires were color coded backwards, but I still felt like an idiot for not doing a quick check before connecting it up.
Click to expand...

Well, the bad news is that your Wife is wrong.
The good news is it happens to bout everyone till they learn the hard way to make sure. :D
 
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