First, I want to thank you for helping me!!! before I go out there I want to make sure of something.
I ran the car-'39 P-8 and caused a negative showing on the gauge. I was told that I needed to "flash" the generator. With the engine off,I just touch a wire from the larger post (armature-?) side of the regulator to the other terminal-this is the battery terminal-?..or
with the car running -ground the field terminal (smaller one) on the generator??..with a continued negative showing ..it would be indicative of another problem-? possibly a generator??Any info would be appreciated. Thank you! Dennis
Hi Dennis I have found thatagood way to check if your generator is charging or not is to run your car at good fast idle, then disconect one of the battery terminals,it doesnt matter which one. If the engine carrys on running your gen is charging if it stops its not ,the engine has to be run at a reasonably fast idle for this test as unlike an altenator it doesnt start charging till it s turning at a good speed
For what it's worth, these cars are Positive ground. If your battery is connected with the wrong polarity the ammeter will read backwards.
I just bought a '49 and I noticed that it is negative ground. Everything seems to work fine except the ammeter runs opposite of the way it should (as mentioned in a previous post} and the fuel gauge does not work. Does anyone know if the fuel gauge not working is a result of the reversed polarity or perhaps its just plain ole broken? Im thinking that if I reverse the connections on the ammeter, it will work the way it should. Otherwise, Im thinking of leaving it the way it is. Does anyone know of a reason why I should switch back to positive ground? Obviously, originality is not a high priority for me. Thanks for any and all comments. George Leonard
Hi George,
1. Are you sure that your car should be negative ground, or could someone have installed the battery backwards by mistake before you owned it?
2. If your car has a steel gas line from the tank to a flexible line leading to the carb, disregard this, but I read somewhere that if you are running rubber fuel lines, you will lose the ground for your gas gauge sending unit.
3. Could be, that neither #1 or #2 applies in your case.
Regards,
Pat OConnor
Hi Pat,
Thanks for your reply. I believe (but Im not certain) that my car should be positive ground and that someone reversed the polarity before I bought it. (I bought it yesterday) Can you think of any reason why I should not just leave it this way? My Dad always told me not to fix anything that isnt broken. But maybe this could qualify as "broken"?
Ill check my fuel lines tomorrow. Thanks for the tip!
George Leonard
George-
I'm fairly certain that all the Plymouths through 1955 were 6 volt positive ground (possibly some sold to the military were otherwise?).
I'll leave it to someone with more electrical smarts than myself to answer what could happen if you leave it as negative ground, or if anything (generator, voltage regulator) might have problems if you switched it to positive ground.
If you can obtain a copy of a MOTOR's manual that covers 1949 cars, they have a lot of good information in them on servicing generators and voltage regulators, including part numbers.
I'll check back later today to see if someone came up with a better answer; if not, I'll see what my MOTOR's manual says.
Right now, I have to get an ignitor for my furnace.
Regards,
Pat O'Connor
I googled "polarizing the generator" and found the following;
POLARIZING THE ELECTRICAL SYSTEM
Whenever a generator or a generator regulator is tested, repaired, or replaced, the generator must be polarized. If this is not done, the generator may be damaged and the regulator contacts burned. Reversed polarity will discharge the battery - or damage it.
There are two types of generator and electromechanical voltage regulator combinations used with DC generators.
In an "A Circuit" system, the field is grounded through the regulator. "A Circuit" systems are found in most Ford and GM vehicles.
Most Chrysler vehicles had a "B Circuit" system which was grounded internally through the generator.
To polarize an "A Circuit" system, connect the FIELD, ARMATURE, and BATTERY leads to the regulator. Connect the battery. Then, momentarily connect a jumper wire between the ARMATURE terminal and the BATTERY terminal at the regulator.
To polarize a "B Circuit" system, connect the FIELD, and ARMATURE leads to the regulator. Connect the battery. Then, just before installing the BATTERY lead, momentarily touch it to the ARMATURE lead terminal.
VC and WC 1/2 ton military 4x4 Dodge trucks without radio set ups had 6 volt electrical systems with the POSITIVE battery terminal grounded.
WC 1/2 ton military 4x4 Dodge trucks with radio set ups had 12 volt electrical systems with the NEGATIVE battery terminal grounded.
The following 3/4 ton 4x4 Dodge trucks had 6 volt electrical systems: WC-51; WC-52; WC-54, WC-59; and WC-60, as did the 1 1/2 ton 6x6 WC-62 and WC-63.
The following 3/4 ton 4x4 Dodge trucks had 12 volt electrical systems: WC-53; WC-56; and WC-57.
All 3/4 ton 4x4 Dodge trucks and 1 1/2 ton WC models had the NEGATIVE battery post grounded
While the voltage was different - 6 volt vs. 12 volt, the steps to polarize the generator are the same.
The old generator with an electro-mechanical regulator is a rugged, versatile set up.
We can convert a POSITIVE Ground system to NEGATIVE Ground by changing the polarity of the battery and the generator; and switching the leads on the ammeter to show a charge when it's charging.
We can also increase the output voltage of a 6 volt generator and use an 8 volt battery by adjusting the voltage regulator. I know of folks who increased the voltage a bit more and use a 12 volt radio with an 8 volt system.
SOURCES:
Automotive Electrical Systems, Classroom Manual and Shop Manual, Harper and Row Publishers
TM 10-1123/1443, Maintenance Manual, 1/2 Ton 4x4 Chassis, Dodge Trucks built for United States Army, Portrayal Press
TM 9-808, 3/4 Ton 4x4 Truck (Dodge), War Department
TM 9-810, 1 1/2 Ton 6x6 Truck (Dodge T-233, Models WC-62 and WC-63), War Department
Thanks, Tim for your researched reply. So youre saying:
"We can convert a POSITIVE Ground system to NEGATIVE Ground by changing the polarity of the battery and the generator; and switching the leads on the ammeter to show a charge when it's charging."
Consequently, you think that it may be okay to leave my car as a negative ground? Sorry if I need to break things down to the basics. Id have made a pretty poor mechanic, thats for sure!
George Leonard
Like many things, different people have varying ideas on what needs to be switched when converting from positive ground to negative ground.? ?And I don't claim to be an expert, either.
I would change the wires on the coil.? The wire that goes from the coil to the distributor goes to ground, so it should be the negative side of the coil on a negative ground system.? Others might not think it's necessary, but people I know that are certainly smarter than me electrically think so; consequently, so do I.
The problem with the fuel gauge mentioned earlier may simply be the grounding of the sending unit.? (nothing to do with pos/neg ground, only that the sending unit is corroded and not grounded.? I can't see that rubber fuel hose would impact the function of the gauge.? The sending unit should be grounded through the tank, through the tank's mounting to the chassis/body.
I find that probably 99% of electrical issues are related to ground.
George, You shouldn?t try this conversion without electrical experience. You don?t really have any disadvantages when leaving it with minus grounded- other than not beeing original. The coil e.g. usually is a kind of transformer and not polarity sensitive. Mybe there are other kinds of coils. If You don?t have any electric featutres added later, maybe only radio and generator are polarity sensitive. Anyhow, You better look for experienced advice.
Greetings! Go
George
it is quite simple to check if you polarity has been changed , simply disconect one battery terminal (any one will do ) touch the lead back on to the battery post with the ignition on if it gives a massive spark the polarity is the wrong way , as i said only touch as it will be a big spark. if it proves to be alright i would say that someone has converted it with out changing the wires on the ammeter . over the last 20 years i have converted 4 cars to neg to ground, the only wires you should have to change are the ammeter and as tim says the coil wire, unless you have a radio or some other accessory that is polarity sensitive. the gen is not .
Well, right now Im inclined toward leaving it as it is since noone has given me any reason to do otherwise. I think that what happened to my particular car was that it sat for seven long years and thus lost any vestiges of a polarized electrical system. When the guy who sold the car to me hooked it up for the first time with a negative ground (as most people might), the system just developed that characteristic since it had none of its own. Most likely, if he had hooked it up properly with a positive ground we would not be having this discussion right now.
I later learned that some people do this intentionally to make it easier to hook up aftermarket accessories such as a radio. So far as I know, their cars did not suffer any long term detrimental effects. So, Ill just leave it 6 volt negative ground. If everything should burn up at some later date, Ill just switch over to 12 volt negative ground and replace everything that needs replacing. Does that sound like a plan? I know some people just wince over any departure from originality and to them I apologize. But remember, all this could be changed back fairly simply if my car ever winds up in the hands of a purist.
Thanks for everyones help and patience.
George Leonard