Packard Aerodrive

[RO]

I'll have some electrical schematics to post later, but need someone familiar with the 1941 Packard 120 overdrive known as AeroDrive. The original AeroDrive was controlled via a 6-terminal relay that drove a lockout switch, kickdown switch, Governor, and of course the Solenoid. There is the typical mechanical cable link to the solenoid as well. This is known as the "full electric" overdrive. Needless to say, the car was 6 volts as from the factory. The original type overdrive solenoid contains 4 terminals, those being the "typical terminals" usually always labeled 4 and 6 but in addition terminals 3 and 7. Terminal 7 merely runs back to an indicator light on the dash and thus is no issue here. Terminal 6 reacts to the relay terminal 6 and momentarily grounds the ignition as the solenoid pawl engages.....taking the load off the driveshaft so the pawl can engage. When the relay closes, the current leaves the Relay Post #4 and enters the overdrive solenoid at its post No. 4 and energizes the heavy "pulling" coil in the solenoid. The No. 3 circuit is completed at the same time and energizes the light "holding" coil.

Now to my question:

The car has been converted to 12 volts with an alternator. I have been advised that I cannot merely insert a voltage reducer in the wiring to the solenoid because it just will not work due to sensitivities in the holding coil, though I'm still pondering this. The perceived workaround I have come up with is to use a 12V overdrive solenoid from a 1957 Nash Rambler. The relay, kickdown switch, lockout switch, and governor should NOT be sensitive to voltage, just the solenoid.

The problem is the 12 V solenoid has no "Terminal 3" but just the Terminals 4 and 6. Does anyone know if in the 12 volt OD solenoid design, the No. 4 Terminal has been "modernized" to react like the old 6-volt solenoids terminals 4 and 3. That is, will the single 12 v solenoid terminal 4 do the job of both "pulling" and "holding" the coil? I need to try and gte this 12 volt solenoid to engage the pawl for the overdrive to function.

I'll try to post the wiring schematic later on once approved.

[RO]

http://www.aaca.org/photopost/showphoto.php?photo=3231

[RO]

http://www.aaca.org/photopost/showphoto....&page=1

[RO]

Here is the electrical schematic of the original 6-volt AeroDrive:

http://www.aaca.org/photopost/showphoto....&page=1

[RO]

OK, that schematic scanned and uploaded clearly.

What I am trying to do is maintain all orginal components (or slightly modified) but replace the 6-volt activated solenoid in the schematic with a 12-volt activated solenoid with only TWO terminals, labeled 4 and 6 which serve the same function as the 6-volt, but Terminal #3 is where the glitch might be.

[Guest imported_PackardV8]

at this point i can only recommend that u look at the wiring diagram for the Nash 12v system and compare it to the Packard diagram. OR, look at the 12v solenoid to see if it has heavy AND lite pulling coils. It might be that the Nash 12V uses only ONE coil. The 2wo coil config of the 6ix volt might be because 6ix volt systems operate at high amperage levels nearly twice that of 12v.

[RO]

Good thought. I have the '57 Rambler wiring schematic but it doesn't detail the solenoid. I may just pull the solenoid apart and see what's in there. I just got started on this this week with first a total rewiring of every single wire associated with the overdrive. It's difficult to work on with previous mods being made by other folks in an attempt to get it working. Bottom line, of course, we hope to make the 12v solenoid work. OD on this car reduces effective engine speed by about 27-28% or so.

[Guest JT]

RO, the newer solenoid internally switches from the pull in coil to the hold in coil therefore using just one terminal. But I would think you would also have to use a 12 od relay to work with that 12 volt solenoid.

I don't know why you couldn't use a voltage reducer to power the original setup with 6 volts though?

[RO]

I've looked at schematics of the Rambler, Kaiser, Hudson, Chrysler/Dodge/Desoto/Plymouth, and Ford/Mercury over several years in the mid 50s and all have just the terminals 4 and 6 but all appear to have two coils with what appears to be the #4 post terminal activating both in some parallel fashion.

[Guest JT]

No. 4 is for the coils and no. 6 is the grounding terminal that runs to one set of contacts on a kickdown switch that then goes to dist points (unlike the R9 setup in which it runs through relay as well).

When the no. 4 terminal is energized it activates both coils to pull in. Once plunger is pulled in an internal contact opens and disconnects the heavy coil.

[Guest JT]

Not to confuse things but I mentioned the no.6 above due to IF you did have to use the newer 4 wire relay there would be no terminal on it for the dist grounding out wire and you would have to change to a four terminal kickdown switch, otherwise as you already know no. 6 performs the same function on both solenoids.

[RO]

Thanks JT. I obtained this 28-page booklet written by Randy Rundle from Patrick's Antique Cars & Trucks in Casa Grande, Az. The title of the booklet is "The Official 12-volt Conversion Guide." The booklet has a section on Overdrive Transmissions and states the folowing:

1. "The orginal 6-volt Governor, Relay, and Kickdown Switch will all work fine on 12 volts. Only the overdrive solenoid is affected by the change to 12 volts."

2. A voltage reducer will not work on an overdrive solenoid because there are actually two different coils inside the solenoid housing. One set is the heavy pull-in coils, which engage the OD. The second smaller set is called the holding coils. They hold the OD engaged while it is in use. Both sets of coils require different amounts of current to work properly. The smaller holding coils are the ones that will be destroyed first from excessive voltage....."

#2 above as stated is why I am still pondering because the last line refers to excessive voltage which doesn't seem to be answering the question relative to a voltage reducer in the line(s).

From all the parts I got with the car, it would seem someone in the past has tried a 4-post relay and I as well am pondering that. Also, I have seen in some of the other OD wirings for cars the 4-terminal Kickdown switch, but was trying to keep this thing as simple as possible and hoping to retain the KDS already in place.

[RO]

If it should turn out that in trying to stay with the original 6V solenoid that a 12v to 6v reducer will not work for the original solenoid, then I think that perhaps an alternative is to use a resistor in the wirings to the solenoid. Due to the different current draws, this would mean three different resistor sizes, but maybe this is a perceivable.

[RO]

OK, I am about to get back on this '41 120 Aero Drive overdrive. Again, we will be using a 12-volt solenoid on this 120 converted to 12V. I plan to make the simplest hookup I can to enable the overdrive to engage. I have been told by 2 or 3 folks that I can just energize directly to the overdrive solenoid by a toggle switch; that is fine, but the solenoid has two terminals labeled 6 and 4.

It "appears" I would hot wire (via the toggle switch) to terminal 4, but then do I just ground the terminal 6 based on "No. 4 is for the coils and no. 6 is the grounding terminal?" We will have no relay, no kickdown switch, and no governor in the final assembly. The toggle switch will do what I believe needs to be done and greatly simplify this. (I saw a Kaiser done this way and a Studebaker, but unfortunatley did not get to observe the wiring or talk in details to the folks.)