Generator polarity?

Copeland

Member
First, thanks again to everyone who gave advice last week on how to get out the stuck bolts. Your suggestions worked, and now I have a good seat on the tractor. I'd appreciate it if I could ask another question. My tractor is a 1946 Farmall H tractor that has been in the family since new, now it's mine. It had been sitting for years, but to get it to me all my cousin had to do was put in new gas, a new battery, and she fired right up. He drove it up on the trailer and brought it to me. I then started it up, backed it off at my place. Later I started it up again to run the carb dry so it can sit while I do restoration. Today I discovered my cousin had hooked up battery with negative to ground, which is opposite of what it should be. I'm amazed it started those three times that way. After I discovered this, I saw my older neighbor with a farm down the road. I asked if I could just switch the battery cables to normal and fire it back up, and he shook his head and practically yelled at me. He said if I didn't first re-do the polarity on the generator, I'd burn up all the electric on the tractor - yikes! So, I have two questions. First, did starting it up those three times on negative ground automatically re-do the polarity of the generator so that I just cant switch the cables now? Second, if I have to re-do the polarity of the generator, how do I do that? Thanks, in advance, for your help again. I love this tractor and don't want my amateur restoration skills to ruin it! Jeff
 
Most of the electrical stuff on that tractor pretty much does not care if it is hooked up + or -. As for the generator to have it charge yes it does need to be polarized but that too can be done for either ground
 
(quoted from post at 13:22:14 03/28/20) First, thanks again to everyone who gave advice last week on how to get out the stuck bolts. Your suggestions worked, and now I have a good seat on the tractor. I'd appreciate it if I could ask another question. My tractor is a 1946 Farmall H tractor that has been in the family since new, now it's mine. It had been sitting for years, but to get it to me all my cousin had to do was put in new gas, a new battery, and she fired right up. He drove it up on the trailer and brought it to me. I then started it up, backed it off at my place. Later I started it up again to run the carb dry so it can sit while I do restoration. Today I discovered my cousin had hooked up battery with negative to ground, which is opposite of what it should be. I'm amazed it started those three times that way. After I discovered this, I saw my older neighbor with a farm down the road. I asked if I could just switch the battery cables to normal and fire it back up, and he shook his head and practically yelled at me. He said if I didn't first re-do the polarity on the generator, I'd burn up all the electric on the tractor - yikes! So, I have two questions. First, did starting it up those three times on negative ground automatically re-do the polarity of the generator so that I just cant switch the cables now? Second, if I have to re-do the polarity of the generator, how do I do that? Thanks, in advance, for your help again. I love this tractor and don't want my amateur restoration skills to ruin it! Jeff

Is it possible the battery was installed (-) ground in the past and the tractor operated that way? It's impossible to know that, but it's sure possible.

Was the generator charging when you had it running? Did the Ammeter read charge or discharge? If it went to the CHARGE side, it would indicate someone changed the tractor to (-) ground in the past.

If it WAS charging, it IS polarized to charge (-) ground.

If it DID charge when you had it running, and originality is not an issue here, personally, I'd leave it "as-is".

If magneto ignition, the mag isn't involved in the charging system and doesn't care about battery polarity.

If battery/distributor ignition and the coil is wired properly, for (+) ground, the (+) terminal on the coil will be connected to the primary terminal on the distributor.

If wired for (-) ground, the (-) terminal on the coil will be connected to the primary terminal on the distributor.

Post back with what you've got/how it's wired.
 
presuming it is still 6 volt. I have seen so many times the battery neg. gets hooked to ground. the ammeter will show discharge. hook the battery to pos. ground and all will be good. and yes tractor will start with grounded either way.
 
Polarity will not matter if all equipment is original, as nothing is solid state. I prefer to leave 6V as positive earth and make all 12V as negative, it just seems more likely someone will hook up correctly in the future. Might as well polarize the generator once all is hooked up.
 
You mentioned generator so is it a generator or alternator? If it has been changed to an alternator, the change over usually requires battery negative to tractor chassis. That also means it is usually a 12 volt battery instead of the original 6 volt. The neighbor "yelling" could mean he was thinking of the damage to the alternator if battery cables are reversed on an alternator system. Certainly you wouldn't "burn up all the electric" but the alternator would (could?) be damaged.

Some electrical folks who post here have said a 6 volt alternator is available. I don't know about 6 volt alternators so no comment on that. So it may still be 6 volts with a RARE 6 volt alternator.

A bit more info from you will help us to help you. Thanks
 
Good questions, its impossible to say from here if it ever had its polarity changed or not but here are some guidelines to follow:

1) A generator can charge at EITHER battery polarity and once properly polarized and configured correctly it can work fine.

2) NOTE if in doubt one should Polarize BEFORE start up because if the genny were polarized opposite from how the battery is installed the Voltage Regulator might be damaged.

3) TO POLARIZE the Generator once the battery is installed and BEFORE start up, use a jumper wire to momentarily flash jump from BAT on the VR over to the GEN/ARM terminal and you should get a small spark. If its a cutout relay instead of a VR its still the same BAT side over to GEN/ARM side to polarize BEFORE starting...

4) If a working ammeter is installed correct and polarity is matched if you turn lights or ignition (unless a mag) on, it should swing over to - discharge, then when running at fast RPM if alls well it should swing over to + charge. If an ammeter does just the opposite the polarity must have been changed and to make the meter work right swap its leads side to side.

5) If its a battery powered coil distributor ignition polarity does matter. For POS ground the coils - gets voltage when IGN is ON while the + wires to distributor. For NEG ground its the opposite. + from ignition switch and - to distributor.

6) If the genny is working at fast RPM battery voltage should rise from say 6+ or so up to at least 6.5 to 7 volts subject to RPM, battery and genny condition. Twice that on a 12 volt system.

7) As is, does the ammeter show + charge at fast RPM and a small discharge when off and lights or ignition ON ?? If so it must be okay. If it does the opposite, discharge at fast RPM but + charge with lights or ign on not running, the ammeter needs its leads swapped. HOWEVER if batt voltage rises (see above) at fast RPM it must be charging !!!!!!!!

8) To be safe I would polarize,,,,,,,start up,,,,,,,see what ammeter shows running and not running with lights/ignition ON,,,,,,,,,,,,,see if battery voltage rises at fast RPM (if so must be charging).

If 6 volt it was likely POS ground original and Id keep it that way. If so install battery at - ground,,,,,,,Polarize the Genny,,,,,,,,,start her up,,,,,,see if ammeter registers correct and battery voltage rises at fast RPM...

NOTE this is for GENERATOR not an Alternator. Most Alternators are for NEG ground.

NOTE BOTH the Genny and VR need a good ground to work

NOTE you asked if starting on Neg ground automatically re did the Polarity. It may have damaged the VR if genny polarity was opposite from battery installation. Sorry, I cant say from here what happened when you started it (don't know if polarity was right or not???) or how it was wired before or got changed ??? so just Polarize BEFORE starting and see what ammeter does and see if battery voltage rises at fast RPM ??..

Nuff said for now, let us know

Best wishes yall keep safe and God Bless America in these difficult times

John T
 
Last I knew the diameter of the - and + posts on batteries are not the same, so it's a little difficult to hook a battery wrong.

Dusty
 
(reply to post at 17:22:14 03/28/20)

Ok, guys, now I'm REALLY confused! I just went outside, hooked up the battery with the negative side to ground (I can't start it because I drained everything to clean out the tank), then I switched on the lights. When I did that, the ammeter shot up the right side (charging)! Then, I pushed in the starter just a minute, and the ammeter also went to the right. I then switched the battery so that I put positive to ground, and when I turned the lights on again, the ammeter went to the left (discharge)! However, Dusty was right -- the one cable end was too big for the terminal, and the other was too small. So, what is going on? It looks now like it should be positive ground, but then why is the negative post on the coil wired to the main post on the distributor? Help! I'm confused now more than ever! Jeff
 
(quoted from post at 20:16:39 03/28/20)
(reply to post at 17:22:14 03/28/20)

OK -- maybe I just thought of something. What if it really is positive ground and it is the *ammeter* that is wired wrong. What if I switched the wires on the ammeter and then tried again. If, with the wires on the ammeter switched, if the lights are on and the needle goes to the left (discharge), would this then mean it should be positive ground and just the ammeter was not wired correctly? Help! I'm grasping at straws here because this is getting more confusing as it goes!
 
ok,... your ammeter is functioning correctly for pos. ground. the coils is not hooked up correctly . positive on the coil goes to the distributor. if its not factory original no way of knowing who played with it or what they have done. just change the coil wires so pos goes to dist. and all should be good.
 
Battery positive to ground, engine not running, lights on, and the ammeter showed discharge --That is what it should show. As for the way the coil is wired just swap the wires around. It is most likely the coil got changed or wiring worked on over the years and was it hooked up wrong for positive ground at that time. Coils will work wired either way, just better with the proper ground to the distributor. It would be more work to change the ammeter wires than the coil. Most would only change the ammeter wires if converting to a negative ground alternator. I don't see any gain to change the ground of a generator system. Polarize the generator to positive ground and you should be good to go. Whether or not the regulator was damaged will have to be checked once it is running.

The battery cable terminal ends, especially the universal replacement ones, can usually be opened up or collapsed to fit either battery terminal post.

Just my thoughts, others will likely vary.
 

Ok, guys, now I'm REALLY confused! I just went outside, hooked up the battery with the negative side to ground (I can't start it because I drained everything to clean out the tank), then I switched on the lights. When I did that, the ammeter shot up the right side (charging)! Then, I pushed in the starter just a minute, and the ammeter also went to the right. I then switched the battery so that I put positive to ground, and when I turned the lights on again, the ammeter went to the left (discharge)! However, Dusty was right -- the one cable end was too big for the terminal, and the other was too small. So, what is going on? It looks now like it should be positive ground, but then why is the negative post on the coil wired to the main post on the distributor? Help! I'm confused now more than ever! Jeff[/quote]

OK -- maybe I just thought of something. What if it really is positive ground and it is the *ammeter* that is wired wrong. What if I switched the wires on the ammeter and then tried again. If, with the wires on the ammeter switched, if the lights are on and the needle goes to the left (discharge), would this then mean it should be positive ground and just the ammeter was not wired correctly? Help! I'm grasping at straws here because this is getting more confusing as it goes![/quote]


Here's my "take" on this... MOST LIKELY when it was last used the battery was connected up in the manner the cables fit.

When you ran it, if no smoke was let out of the generator or cutout that makes it more likely that it WAS run (-) ground in the past.

It MAY have been run like that (-) ground for a long time and no one even noticed the Ammeter reading backwards.

It would be interesting to start it up and measure the generator output voltage. If it is charging/outputting about 7.4 Volts (+) that would prove it's functioning and charging (-) ground.

Same with the coil... if it was installed by someone who knew what they were doing the way it was connected would indicate the tractor was being used (-) ground.

But if someone just slapped it on without knowing about or checking polarity there's a 50-50% chance they got it right.

The coil will spark and the engine will run which ever way the coil is connected, conventional wisdom is that the spark is 20% more efficient when connected properly, making for less chance of misfire under heavy load or other tough operating conditions.

You could swap the leads between the ammeter terminal posts and leave it (-) ground and all will be well.

IF you WANT to change it back to (+) ground, swap the leads at the coil, swap the large and small battery cables, then polarize the generator BEFORE starting the engine.

This is done by momentarily jumpering the "BATT" (has power all the time) and "GEN" (sometimes marked "A" or "ARM") terminal on the cutout or VR (if so equipped).

If you start it WITHOUT doing this first, there's a good chance of "killing" the cutout/VR and/or the generator.

For a good "read" on polarizing, copy the link below and paste it in your browser. (It won't post here as a clickable link.)

From the menu page, click on and look at Pages 50 and 51. (Original page numbers on scanned pages are 49 and 50.)

There's LOTS of other good IH/Delco electrical system information in that book "GSS-1310 Electrical" as well.

http://farmallcub.com/rudi_cub/www.cleancomputes.com/Cub/Blue%20Ribbon%20Service%20Manuals/GSS-1310%20Electrical/index.html
 
(quoted from post at 20:52:22 03/28/20) Battery positive to ground, engine not running, lights on, and the ammeter showed discharge --That is what it should show. As for the way the coil is wired just swap the wires around. It is most likely the coil got changed or wiring worked on over the years and was it hooked up wrong for positive ground at that time. Coils will work wired either way, just better with the proper ground to the distributor. It would be more work to change the ammeter wires than the coil. Most would only change the ammeter wires if converting to a negative ground alternator. I don't see any gain to change the ground of a generator system. Polarize the generator to positive ground and you should be good to go. Whether or not the regulator was damaged will have to be checked once it is running.

The battery cable terminal ends, especially the universal replacement ones, can usually be opened up or collapsed to fit either battery terminal post.

Just my thoughts, others will likely vary.


Thanks, Jim! I'm going to go with your suggestions. You explained this very clearly, and I appreciate that. I'm going to switch the coil wires, re-do the polarity, and go from there. Thank you -- and bless you all for your help. Take care, everyone, and stay well! Jeff
 
Has it been changed from MAG to distributor? Orignal it had a mag and coil is inside mag where you cannot see it, distributor outside. Then they had a voltage control built into light switch, low charge, high charge dim lights or bright lights. Most are assuming it does not have this type of light switch. Grew up with a 41 H with mag that was changed to distributor because of starting problems because no one knew how to work on a mag back in 60s-70s. And at that time no one even thought about hooking up systen with neg ground or changing to 12 volt.
 

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