PDA

View Full Version : Q. - 55 Commander Electrical + or -



Frank Starr
06-13-2007, 07:45 PM
I posted this on the General Discussion Forum, but it probably belongs here on the Technical site.

Had an interesting point of departure on the 55 last night. It's been up on jackstands for awhile while we do things like replace muffler bearings and install Saginaw power steering. Anyway, I went to re-install the battery. Being a little fuzzy on which terminal was grounded, I checked the shop manual, which of course states the positive terminal is grounded. So I installed the battery accordingly, so that the respective cables would reach the respective terminals.

My first clue was the ground cable would not fit on the + terminal of the battery - it was too small. My second clue was the hot (starter) cable was oversize, loose and rattling around on the - terminal. What the heck??? This was the battery I took out of the car, and everything fit fine then.

HMMMMMMMMM. The only solution to this conundrum was that the battery had been installed the other way 'round, so that the - terminal was grounded, opposite of the factory shop manual.

This was the point where time slowed down. This would mean the car has been converted from + to - ground. So the generator, starter and regulator, for a start, would be opposite polarity. Well, as a matter of fact, the generator is obviously not the original (it's an Autolite, not Delco, and it's too long), and I'd noticed the regulator looked new. The starter is wrapped in some insulating cloth, so I don't know what it is, but it sure starts the car in a hurry. Wonder if the Ammeter and Fuel Gage are connected backwards too.

But why? Looking around, my eye fell on the air conditioner compressor. Aha. That has an electromagnetic clutch in it, which presumably would need the correct polarity to operate properly. So my question: Was the car converted from + to - ground when the AC was installed (aftermarket), simply because the compressor clutch units were only available for - ground systems? Has anyone heard of this parctice?

Ya gotta want AC awfully, awfully bad to do that.

Frank Starr
Seattle (no we don't need AC) WA

ps - it's a good thing I still had the battery I took out of the car. Otherwise I would have gone back to whoever I'd bought a new battery from screaming about their battery having its terminals backwards.

Tom B
06-13-2007, 08:01 PM
Is it a six volt battery or a 12 volt battery? '55 should be 6 volt, positive ground. I'm not sure polarity would affect an electro-magnet.

[img=left]http://www.alink.com/personal/tbredehoft/Bothcars.jpg[/img=left]
Tom Bredehoft
'53 Commander Coupe
'60 Lark VI
'05 Legacy Ltd Wagon
All three Indiana built OD cars

Frank Starr
06-13-2007, 08:12 PM
It's 6 Volt.

An electro-magnet, like any magnet, has a positive and a negative pole. I haven't been inside the AC clutch unit so I don't know how its made. If the design is polarity-sensitive, then battery polarity would affect it. I'm going to check it tonight.

Why else go to the work of changing the car's polarity?

Frank Starr
06-14-2007, 10:51 PM
Update -

I checked the AC clutch. As TomB implied. it's not polarity sensitive, and worked with either + or - grounded. So then I checked the defroster fan and AC fan, and they were both fine either way too. The newish regulator has "NEG" stamped on it, which should imply negative ground. The coil has been reversed as installed on the car so that the coil (-) terminal is connected to the ignition switch. The ammeter wiring is as original, as the needle indicates "charge" when you turn the headlights on (engine not running).

So someone has gone to a lot of work to change the polarity on this car from (-) ground to (+) ground, for no apparent benefit.

Why???

Tom B
06-15-2007, 02:34 AM
Why? maybe because they didn't know better? Put a pos ground voltage regulator in it, connect the battery properly, prime the generator (momentarily connect the batt and field terminals on the regulator) correct the coil connections and run with it.

[img=left]http://www.alink.com/personal/tbredehoft/Bothcars.jpg[/img=left]
Tom Bredehoft
'53 Commander Coupe
'60 Lark VI
'05 Legacy Ltd Wagon
All three Indiana built OD cars

Frank Starr
06-15-2007, 12:00 PM
Tom -

That's pretty much where I am with the situation too. There have been a number of other examples of 'don't know any better' on the car, so that would fit. Among other things, somebody had put a hand throttle on it, consisting of a cable to the carb mounted through the dashboard. Why? It never fails to amaze me what people do to old cars.

Thanks for your responses.

Frank