Packard Forum Index » V-8 (1955-56)

I'm thinking about having the radio in my '55 (positive ground) converted to an AM/FM radio. On the outside, the radio would look the same and the Wonder Bar would be functional I would get Bluetooth capability for hands free cell phone. However, the guts that would go into a positive ground system would cost more and the radio would be of lessor quality.

Therefore, it seems to be a fairly simple matter to convert the '55 to a negative ground system based on what said about an earlier post of mine. If I'm correct, in addition to changing the battery the following would also need to be done:

1. Re-polarize the generator
2. Change the input/output wires on the amp meter
3. Change positive/ negative wires on the coil.

Am I wrong or is there something that I'm missing?

Other than possibly having solid state devices somewhere else you have covered the needed changes. A modern Instrument voltage regulator and the reworked torsion level control switch are a couple of items that could have been replaced with a solid state device which would not appreciate the swap.

There is a question on the original voltage regulators. I don't recall anyone mentioning an issue after a swap and there have been plenty of swaps done accidentally or on purpose so there is probably nothing to worry about. Just be aware that for whatever reason some voltage regulators Packard used are labeled positive and negative. Auto parts stores also list many replacements as pos, neg or universal.

Without knowing exactly the differences as to why some regulators are categorized pos or neg it is hard to say if the old one would cause any issues. If there are unexplained or odd charging behaviors after the swap that a repolarization does not fix keep the regulator in mind.

Howard thanks for your input. As you can see from the linked reference on the car when I received it back in September 2017 it was hooked up with a negative ground and the amp meter went backwards. Therefore, I'm assuming the TL was not converted to a polarity sensitive solid state system.

I'll keep the voltage regulator in mind if there are charging problems after I flip it over.

Again Thanks

Was the clock switched..

What about fuel gauge..water..oil pressure..does it matter with them.

It shouldn't matter on the gauges other than the ammeter but perhaps motors such as the heater blower might have to be switched over to the 1956 versions. Not sure about power window and seat motors as they can possibly have their wires reversed if necessary.

Best thing is to look through the 1955-1956 parts book to see if there were part number changes but even if there were, it's not conclusive as it could have been a simple change in gauge pointer or back color. Still, it's a place to start.

Motors in a stock Packard have separate field and armature coils. The motors are wired internally to always have the same magnetic N-S pole relationship between the field and armature so a polarity swap feeding the motor makes no difference since both field and armature will change at the same time and be affected the same way. To make the motor change direction there would need to be a switching of the coils so typically 4 wires exit the motor. A switch would then be used to change magnetic relationship on either the field or armature while the other stayed the same and thus direction is changed. Packard did this with the the prewar Deluxe heaters and hydraulic windows where a switch made the motor run one direction for defrost or window up and the opposite direction for heat or down. Reversible motors post war have two separate field coils wound in opposite directions for the different magnetic fields needed to change direction but only one field coil is used at a time. The armature is wired so it always keeps the same relationship to the fields. One exception may be the 54 electric seats which I believe have relays to swap the field or armature as was done prewar and the other is the 56 push button shift motor.

If a window or heater motor has been changed to one of todays permanent magnet field type motors then those are definitely polarity sensitive and wires would need to swap. Believe the high torque mini starters also fall into that category as would most likely many of the aftermarket AC units. If any of those have electronic temp and speed controls then it would get even more interesting if there are no reverse polarity safety circuits built into the units.

Packard used both thermal and magnetic type gauges so there is either a heater coil wrapped over a bimetal strip or two opposing magnetic coils --again always in the same relation -- making them move. Those don't care which direction the current flows so not polarity sensitive. Where that would change is if the car uses an instrument voltage regulator to supply the 5v gauge heater voltage and the old heater and bimetal type regulator has been changed to a modern solid state device. Those most definitely do care.

Your T-L system may stop working. I worked on a '55 Caribbean that had been converted to negative ground,the solenoids now needed +12VDC to operate instead of ground. I replaced the relays inside the timing box and re-wired it to send out +12VDC and it worked.

Everything will work just fine except the ammeter will read backwards. All other things "worried" about are non-events. Back in the day many 55's were inadvertently switched to neg ground when the battery was replaced by mechanics not in the know.

Thanks
James From
Kanter Auto Products

I'm curious whether this swap has taken place or if anyone else can answer a question. My '50 was converted to negative ground before I got it. Everything works, including the radio, clock ammeter and all the lights. The only thing that does not work is the fuel gauge. Could this be due to this change? I realize there are other reasons for the gas gauge to stop working. I was just wondering if this could be it.

PS To correct myself, I'm not exactly sure if the heater fan works either.

Except for the AMP Meter, I have not found and gauges in a Packard the are polarity specific.