Converting from positive to negative ground
This article was written by Gary Durborow and appeared in the July 1982 issue of the Tigers East/Alpines East newsletter.
Submitted by Tom Wiencek
August 19, 1996
Judgine by the amounts and types of questions I receive about the subject, many owners of earlier models of our marque are discouraged by the hassles associated with positive ground electrical systems. Seemingly simple tasks, such as mounting a C.B. or tape deck, can become major projects when you have to keep them from touching other metal parts.
Unlike other problem areas, though, this one has a solution that is actually very straightforward: reversing the polarity of the charging system. For all models except those with radios, electrical tachometers and clocks, there is little more to it than reversing a few wires.
The procedure is as follows:
1. Disconnect both terminals of the battery
Lift the battery from the box and put it back in so that the terminals are at opposite ends from the original position. Positive will now be where negative was and vice-versa. Do not reconnect the battery yet, but make sure the existing cables are long enough. Sometimes the positive cable may be a bit too short, depending upon the battery in your car. Usually though, enough extra length can be obtained by taking up some of the slack where the cable runs under the boot.
2. Coil
Unplug the wires at the ignition coil and replace them on the opposite posts. The wire from the distributor should now be to the negative (-) side of the coil, and the wire from the ignition switch will be to the positive (+) side.
3. Ammeter
For the ammeter, simply switch the two plug-on wires as was done with the coil.
4. Radio
If your car is equipped with a radio, it must be disconnected and removed. Depending upon the radio you have, the polarity must be changed either by a switch on the case, or by internal wiring changes. In either case, most radios that operate on positive ground have instructions for polarity reversal somewhere on the case. If equipped with a switch, the change is easy. If the reversal is internal, it is best left to a radio repair person.
5. Electrical tachometer (series IV only) and clock
These two guages were not designed for polarity reversal so it must be done by internal modification. Local electrical shops who are not familiar with the changes necessary may not wish to attempt the job. This service is available, however, from Tiger Tom for a nominal fee of $5 per guage, plus shipping.
6. Reconnect the battery
7. Repolarizing the regulator
Use a small piece of wire and momentarily (about one second) touch it between the regulator terminals marked "Al" and "F". It will make a few sparks so don't think you've hurt something.
At this point, you're finished with the polarity changes. The only thing left is to test the charging system output.
Ideal specifications are: No-load (all electrical items off) - output should be 14.5 to 14.7 volts at 2000 to 3000 RPMs.
Loaded (all electricals on, such as wipers, heater, lights, etc.) - output should not drop below 13 volts at 2000 or more RPMs.
If your readings do not fall into this range, the regulator will need to be adjusted.
And, that's it! Now you're ready to mount that tape player you received for your birthday! Isn't that easier than trying to find al those rubber grommets in the right size?
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