Can my T-Bird engine actually turn over and run normally with battery leads reversed?

My 1962 T-Bird was in the shop late last year (new trans, starter relay, battery, assorted cables) and seemed to work well for ~ 5 mo (~ 500 mi). In May, after returning home from a pleasant Mother’s Day drive, I came back out to the car and it simply failed to start, although there occasionally was a weak click when I turned the ignition key. When I looked under the hood, I discovered that the shop had apparently installed the new battery with its leads reversed, ie., with the positive terminal lead grounded to the chassis and the negative lead connected to the relay (see attached file). It seems very hard for my friends to believe, but my car had appeared to function normally in spite of this. Is it possible for the car ignition (and other electrical components) to work with a reverse polarity battery connection ? Do you have an idea of how serious my problem is likely to be and what the most likely diagnosis / repair sequence would be ? Thanks for your help.


You might want to check to see whether your car is positive ground before doing anything.

Yes, points and coil ignition will function just fine with reverse polarity. The electric starter will still turn the same way because both the field and armature polarity reversed. Headlights don’t care about polarity. If it’s old enough to use a generator, even the generator can be reflashed to charge reverse polarity.

Thanks for the comments, fellas. I also posted this under the “repair and maintenance” thread, so you can see the lively discussion there as well. Bottom line is that a re-polarization of the generator is probably needed and possibly some other ignition components that will need to be checked. Because of the relative simplicity of the electrical system, there are not too many things that are likely to have been compromised. Still, it is rather amazing that it did not show signs of problems until it failed to start, after 500 miles of “normal” function.


I know. That is rather sad, since it I had worked prior to going to the shop. C’est la vie.

If you are lucky, the radio may work once the battery is connected properly.

If it was old enough to have a vacuum tube radio, it might even work. These radios used an electomechanical multivibrator that chopped the DC into square wave AC that could be stepped up to the 200 or so volts needed for the vacuum tube plate voltage. The hum you hear when you first turn on these radios is the multivibrator.

I think that the vacuum tube radio that required 200 volts for the plates of the tube were gone by 1962. There was a radio made by Motorola that was standard equipment in the AMC products in 1960 that had vacuum tubes that only required 12 volts on the plate and hence the electomechanical multivibrator wasn’t needed. I think, though, by 1962 all factory supplied radios in cars were transistors. Some of these radios weren’t ruined by reversed polarity–they just wouldn’t play.

It probably ran until the battery went totally dead–a generator regulator normally won’t work on the wrong polarity (we run across this often with British cars), and I’ve seen regulators fried from this.

Five months?