Packard Forum Index » Pre-War (1899-1942)

Greetings - I'm experiencing an unknown energy draw on my 1929 Chrysler Model 75. In lieu of an electrical witch hunt, I'm planning to do a battery shutoff switch. To avoid future trouble, I plan to do the same with my 1924 Packard Single 8 143. Unless things were changed during a restoration, both are 6 volt positive ground (would someone change the ground and is there a way to confirm if they did?). Can anyone recommend a specific switch you used and liked? Due to battery locations, I would need to run a cable from the battery for a couple feet or so, if that matters. Thank you!

To check the ground polarity just look at what battery cable runs to the frame…

This is a Packard site but your car is a 1929 Chrysler Model 75.

I am a firm believer that with a 6v battery circuit you absolutely want a top quality heavy duty disconnect switch that can carry the high current of the starting motor when that is operating and will be able carry a larger continuous load other times. Avoid the smaller and generally less expensive 12v switches that are too low in current capacity to do a good job with 6v starters and can even overheat and burn. The intermittent starter load is the important capacity and while the larger continuous current capacity is not as critical on the 20s cars with no accessories to speak of, it is important on postwar cars.. Here is a high current quality switch from Jegs that I can recommended but Summit and other vendors should have something similar. I used it on a 47 with 6v and even used the same switch on my 56 with 12v.




For the additional length of battery cable, with 6v use a minimum of 1/0 cable but 2/0 is better. Too small a battery cable and 6v starting motors definitely do not work well together. Several places will make up specific cables with whatever size wire and terminals you specify. Alternately, if your car has a good spot nearer the battery for mounting the switch you could choose to keep it close to eliminate a lot of the extra cable length and with a bit of ingenuity, work the switch by a knob attached to a pull cable or rotary shaft to bring the control to a more convenient location. I have used both methods on my cars depending on where the switch was easiest to mount. For the rotary shaft extension I could have kept and moved the original pot metal switch lever but elected to go with a black knob a bit more visually pleasing.

This is the switch I bought. It has the same current specs as the one Howard provided…300A continuous and 2000A intermittent.
Battery disconnect switch

Yes indeed - as I mentioned, I ran into the problem with my Chrysler, but I did state that I plan to add a shutoff to my 1924 Packard Single Eight.


Packard Don
Re: Battery Shutoff Switch

This is a Packard site but your car is a 1929 Chrysler Model 75.

Thank you all for the helpful responses!!

Hello again - So would any 300 amp or greater continuous and 2000 amp or greater intermittent unit theoretically work? The one that was listed on Amazon, though slightly less expensive, states in the listing that it is for 12v, and doesn't mention 6v. However, one reviewer stated that he used it for a 6v application, and it is fine to do that as long as the amperage is ok. Thoughts?

Also, I'm needing to mount my unit below a floorboard. I'll have to use an extension of some sort to get access to it. I'm having trouble finding something online that would work. Is there such a product or am I just going to have to sort of wing it with a generic rod to sort of push/pull the knob?

Thanks!

Quote:

Service info for the '29 models gives 675 amps stalled and the battery specs imply maybe 200 amps for cranking. (For no load, 50 amps.)
packardinfo.com/xoops/html/downloads/NASD/Models_626_633_640_645.pdf

Interesting to note that these numbers are nearly identical in all respects for the 1954 cars, 25 years later.
packardinfo.com/xoops/html/downloads/servicemanual5154/Specifications_XXI.pdf
packardinfo.com/xoops/html/downloads/servicemanual5154/Electrical_VIII.pdf

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Yes, that's how electricity works. Less volts or less amps means less electrical energy; so for a device like a switch or wire, that only has to transfer electricity and not use it, it will be fine.

The only time this can be a problem is if you want to use something that's rated for like 3+ orders of magnitude more than the actual load. Sometimes it will give odd effects, e.g. a relay that is used to switching 1A, 100V may not cleanly handle a 1mA, 1V signal due to pitting on the contacts. But that's a different story.

Packriots-- Good username. My brass, marine grade Cole Hersee switch below looks similar to what HH56 suggests. Mounted mine on the firewall so just the lever is in the cabin, under the dash, above the clutch pedal, simple, no need to open and close the hood.

Goes without saying to use only solid copper, double aught (00) battery cable, ends both crimped and soldered.

The gear-reduction behemoth starter on my '47 356-ci engine draws more amps than your '29 Chrysler (good cars!) or '24 Single Eight 143, so you'll do fine with the below. NAPA carries them, or shop online:

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