Packard Forum Index » V-8 (1955-56)

Thanks Bernardi, that confirms my thought that there are only minor changes required when switching from POS to NEG ground. The solid-state vibrator is one I hadn't thought of. Just a thought - disconnect the battery when changing the wires on the ammeter All in all, a very simple conversion. I don't know why the A/C would need NEG ground, but they may have some solid-state controls that require it.

Outwardly, things may look old school but most of the Vintage air units have very sophisticated electronic control modules that control everything via digital commands to solid state devices or pulse motors--a far cry from the old turn a knob yank a cable and open a valve or select a different resistor days.

I sent my 55 Patrician's torsion control unit to Snoqualmie, WA for conversion to solid state electronics. My mechanic has put it back into car but informs me that when the three wires are plugged into the proper sockets for a 1955 the system is dead. The contol unit has extra poles apparently for the 1956 models. My mechanic says that it appears to him that the 1956 arrangement calls for the use of as many as six wires. Also, when he plugs the three wires from
the wiring harness to control unit into some of these other poles the system is hot and partially operates to adjust the level of the car. What I am wondering
is whether the rebuilder in Snoqualmie may have rewired the control unit for a 1956 Packard even though my transmittal letter clearly indicated that the
car was a 1955. I would appreciate any advice and help on this problem.


Here are some additional facts to add to this puzzle. Our car is an end of the model year car, which my
father and I picked up in Chicago when the 1956's were already on the showroom floor. I have reason
to believe, then, that the control unit for our car's torsion bar system was a 1956 control unit which the
factory cobbled to take the wiring from the 1955 harness (When my mechanic recently pulled the
control unit off of the car, he found that the three wires coming out of the unit were differently
colored than the three wires coming to the unit from the harness). My surmise, then, is that the
control unit on 1956's is wired differently than a 1955's control unit. So that when I told Snoqualmie that I
had a 1955 Packard, they naturally gave me back a solid state 1955 unit instead of the 1956
that I possible needed because of the aforemenitioned end of the model year swap at the
factory. If this is true, then, is it possible for me to hook up the three wires from the wiring
harness to a 1956 control unit? As I noted in the original comment, the motor is coming on
and moving the short torsion bars when the three wires are run to other terminals in the
unit than the three terminals to which they were hooked when the unit was taken out
of the car. I am thinking this problem might all go away if I obtain another control unit
from a salvaged car, send it to Snoqualmie and have them re-wire the unit to be a
1956 solid state unit, and, then, hook it up as the original unit was hooked up when
it came off of the car. [Remember, my mechanic says that he read the shop manual
and that it says that the 1956's have as many as six wires from the harness to the control
unit].

Something else just came to mind! How many poles does a 1955 control unit have? Since there are only three wires from the harness to the control unit, doesn't it make sense that there would only be three? Since my mechanic is saying that the unit that came from my car has several poles (not just three) doesn't that make it a 1956 control unit for sure?

55 and 56 units are easily distinguished by appearance.

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As O_D has shown, the boxes are different in appearance but internally, the originals were electrically identical. I'm not familiar with details of changes made to convert to solid state, but polarity is an important item with solid state. Has your car still got the pos ground, or is the replacement universal?

Because of the exposed 55 terminals easily corroding, when servicing or the supply of 55 boxes ran out, they were to be replaced by 56 boxes and a short length of 56 cabling which was spliced into the original loom. Those wires were the 56 colors which may explain the difference there.

The difference in number of wires is because in 55 the output of the box ran directly to the limit switches which were then buss barred to the solenoids located right next to them. In 56 the limit switch location was changed so the output from box went as original but the other limit switch wire came back to the outside terminals on the box and then connected to a wire from the solenoids up inside the engine compartment. The outside double connectors are nothing but a tie point--not connected to anything internally, but the 3 in center are identical in function to the 55--just a different type terminal.

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PJ wrote: "As I noted in the original comment, the motor is coming on
and moving the short torsion bars when the three wires are run to other terminals in the
unit than the three terminals to which they were hooked when the unit was taken out
of the car. "

So what's the problem???? It works ok???? Maybe the wire sketch or diagram that hte mechanic made when he took it apart was done incorrectly.

PJ
I recall talking about this unit. You have a 55 Packard with a 56 control unit. I said it may have been because it was a late 55 build but more likely someone in the past had replaced the original with a 56 because Packard Parts had been supplying the 56 unit as the replacement for the 55.

I have attached a wire diagram that shows how to hook up the wires from a 55 car to the 56 control unit.

If I neglected to send this diagram with the control you have my apoligy.

Sincerely, John

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I had to convert my 55 400 from positive ground to negative when I installed a solid state ignition in it. All I had to do was change the battery cables around putting the negative cable to ground and the positive to to the starter motor. I switched the leads on the ammeter and fuel gauge around and polarized the generator and regulator. Everything worked fine and less than an hours work. No problem with suspension and no problem with radio.

There won't be any problems with the starter or the t/l motor when converting from positive ground to negative ground. Also, if you're converting a 6v car, you won't have any problems either, as the 6v starter is actually better built electrically than the 12v starter. Just don't crank forever and ever with it. Going from 6v to 12v makes the starter actually have 4 times the cranking power than it was on 6v. As long as you do what 55panama stated you'll have no problems.