deaddds

Polarize a generator?

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My 37 Olds runs out fine during the day but when there is an electrical load it sputters. This is the first winter ive been regularly driving it so I hooked up the heat box fan. Daytime runs fine w or wo fan running. Headlights on and fan on on a hill the car sputters like its backfiring but if i kill the fan or switch quickly to running lights, the car smooths out. Mechanic put a tester on the gen at the shop and meter says its output is fine but I think the load is putting it over the top when this occurs. Another car guy said i should repolarize the gen and see if it helps. How is this done so i dont fry out something or do i just have the gen rebuilt? Thanks

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If the car has been rewired, or has an electric fuel pump added, you need to be sure the ignition circuit has NOTHING else on it, or you will under volt and under amp the coil and points. It's a common problem. Your ignition switch should ONLY power the primary ignition circuit, NOTHING ELSE AT ALL. This is a common issue is see on many cars. If you need a wiring diagram, just ask, and I will post it. Ed

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If your generator works it doesn't need polarizing. This is usually only necessary if the generator has been taken apart, or occasionally if the gen has been out of service for years. There is enough residual magnetism in the field coils to start it working, after that it magnetizes itself.

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52 minutes ago, Rusty_OToole said:

If your generator works it doesn't need polarizing. This is usually only necessary if the generator has been taken apart, or occasionally if the gen has been out of service for years. There is enough residual magnetism in the field coils to start it working, after that it magnetizes itself.

 

Only quibble I have with your reply is that "been out of service for years" probably should have read "been out of service for decades". :)

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Have a 1959 John Deere 830 tractor, run it once a year in local Labor Day parade. Wasn't charging last year when I got it out, older guy showed me how to take a large magnet and place it on the side of the generator while running to polarize it. Works now.

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That polarization with a magnet is interesting. How exactly is it done ?

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Hi Ed, shoot me that diagram. I know the car has an electric pump that energizes with the key. So that means I need to remove that, right?

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6 or 8? Here are both, if you need a better scan, I will have to take the giant book apart.

new doc 2020-03-16 07.44.53_1.jpg

new doc 2020-03-16 07.43.59_1.jpg

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There was a time when every high school driveway mechanic knew how to polarize a generator. I recall using a length of wire connected to the Batt terminal on the regulator and quickly flashing the other end to , I think, the D post on the generator. East peasy. All this magnetism sounds like hokum to me

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I think Ed has helped find the problem but in case someone sees the title here are the Delco Remy instructions;

 

 

gen pol.jpg

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What does the ammeter do when all this is going on? Does it hover around 0 when you're driving normally? Does it show a charge right after starting and gradually drop to 0 as it tops off the battery? Does it constantly show a discharge and a heavy discharge with lights on? That will help us determine if the generator is even working. If it is working correctly, double check voltage at the battery to be sure the charge is actually reaching the battery. It should show somewhere around 7.5 volts when it's running.

 

Ed's advice is good--too many guys just hook up the fuel pumps to the ignition switch and call it done, but even the smallest fuel pumps will draw 5-7 amps. In a system with 25 amps max, that's a pretty substantial drain. Add in the lights pulling it down even more and you quickly run out of juice to fire spark plugs. I hook my fuel pumps up directly to the battery and use a relay (and/or a toggle) so there's no drain on the ignition but it still goes off with the ignition switch so you can't accidentally leave it running.

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Matt, the ammeter shows just above 0 while running. With running lights only it stays pretty much there. Full headlights about dead even 0. Adding the heater box fan causes the amm to show in the negative. Night driving is clearly negative as the lights are on, the secondary switch for the dash lights are on, add the turn signals here and there and if cold, the fan which is a two level blow. I dont notice any difference if the fan is on low or high. 

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Posted (edited)

If it's keeping up with the headlights then the generator is working properly. The fan for the heater may be overwhelming it, which can either be a short or a tired motor or just one too many electrical loads to deal with. My '41 Buick has a very powerful electrical system and will run everything--lights, fog lights, radio, both heaters--and the ammeter stays right about at zero at cruising speed but shows a deep discharge at idle. That's pretty typical, but my car is also four years newer than your Olds and there were significant improvements in that period. On the other hand, the aftermarket heater in my '35 Lincoln pulls a ton of current and it shows a deep discharge at idle and even at speed the generator can't keep up with lights AND heater running, where it still shows a slight discharge.

 

My guess is that you're simply running out of electricity, which might be normal. The generator should be able to easily maintain a full battery with headlights (it should show a deep discharge at idle but will go positive once you get to about 20 MPH and gradually taper back to 0 as the battery charges). I suspect the heater motor is your problem, not the generator. I don't know the amperage of a 1937 Olds generator, but my '41 Buick is 35 amps and that number goes down as the engine gets hot. So figure maybe 32 amps total. Enough for headlights, taillights, dash lights, maybe an electric fuel pump, but adding anything beyond that may pull more out of the battery than the generator can put back in.

 

Nevertheless, given the stuttering problem, I would double check to make sure your accessories are not connected to the ignition switch. The battery should have enough juice to smooth out those discharges and with a strong battery the car should still run for quite a while with lights and heater, even if the battery is discharging (i.e. the generator can't keep up). It'll eventually run out of electricity, but it'll take a good long while. The sputtering strongly suggests that power is being stolen from the ignition, which says to me that Ed is right about the ignition being the source of power for at least the fuel pump and maybe even the heater. Fix that and I bet your problem vanishes.

 

 

Edited by Matt Harwood (see edit history)
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Most all I have ever seen are type A but here are the instructions;

 

I may be able to look up the series from  your tag number if you post it.

 

Dave

gen series a,b.jpg

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6 hours ago, edinmass said:

6 or 8? Here are both, if you need a better scan, I will have to take the giant book apart.

 

Hey Edinmass, I think that first diagram is probably not a 37 Oldsmobile. It has dual ignition and a 2-brush generator with a 3-unit voltage regulator. The second one looks about right.

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12 minutes ago, Bloo said:

 

Hey Edinmass, I think that first diagram is probably not a 37 Oldsmobile. It has dual ignition and a 2-brush generator with a 3-unit voltage regulator. The second one looks about right.

 

I bet the first one is actually for a Nash. Eight cylinders, dual plugs, N comes right before O...

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Posted (edited)
1 hour ago, Matt Harwood said:

My guess is that you're simply running out of electricity, which might be normal. The generator should be able to easily maintain a full battery with headlights (it should show a deep discharge at idle but will go positive once you get to about 20 MPH and gradually taper back to 0 as the battery charges). I suspect the heater motor is your problem, not the generator. I don't know the amperage of a 1937 Olds generator, but my '41 Buick is 25 amps and that number goes down as the engine gets hot. So figure maybe 22 amps total. Enough for headlights, taillights, dash lights, maybe an electric fuel pump, but adding anything beyond that is going to pull more out of the battery than the generator can put back in.

 

Thats about right for 37, but I am surprised to hear that that the 41 is not capable of more current. I was under the impression Buick stepped it up a bit when sealed beams came along in 1940.

 

There were 3 different generators on 37 olds, according to some old documents I was looking through when working on a couple of 37 Buick generators. The first (early) is a tiny thing, more or less like a 36 Pontiac, maybe 15 amps if you are lucky. The second type is the same as 1937 Buick (except the pulley) and should make about 25 amps or so. It also had a split field so it would work over a wider RPM range. The third (IIRC) is of the same family as the 38 Buick generators, also has a split field, and is only a tiny bit bigger, maybe an amp or two. All are third brush with a 2-unit voltage regulator (regulator and cutout).

Edited by Bloo (see edit history)

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Just now, Bloo said:

 

Thats about right for 37, but I am surprised to hear that that the 41 is not capable of more current. I was under the impression Buick stepped it up a bit when sealed beams came along in 1940.

 

There were 3 different generators on 37 olds, according to some old documents I was looking through when working on a couple of 37 Buick generators. The first (early) is a tiny thing, more or less like a 36 Pontiac, maybe 15 amps if you are lucky. The second type is the same as 1937 Buick (except the pulley) and should make about 25 amps or so. It also had a split field so it would work over a wider RPM range. The third (IIRC) is of the same family as the 38 Buick generators, and is only a tiny bit bigger, maybe an amp or two. All are third brush with a 2-unit voltage regulator (regulator and cutout).

 

Yes, I just edited my post to fix it. The Buick makes 35 amps, not 25. That didn't seem right so I checked the manual.

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2 hours ago, deaddds said:

So how do you determine if you have an A or B system?

 

Good question. I never can remember which is which, and have to look in the manual. I can tell you this: GM cars with Delco charging systems are always or nearly always one type, and Ford with Autolite charging systems the other. Therefore whatever polarization method the Buick people in here use will work for the Olds.

 

It doesn't hold for other makes because both Delco and Autolite made both types.

 

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I did find my listing of tag numbers to series type so if I get a tag number I can say for sure. Most are type A.

 

Dave

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Sorry about the wrong diagram, it was early in the morning and I didn't have my glasses. Here is an interesting FACT. One of my helpers has "IT". Yes, he has it........verified and confirmed with the CDC. He is my next door neighbor, and once every three or four months he helps out around the shop for an hour or two...........he has been quarantined at home, but he is in his 60's and going down hill the last three days..........they are putting him into the hospital this afternoon. I feel fine, but can't do the math to figure out his exposure time......I think going to Amelia for an entire week saved me from exposure to him when he had it with no symptoms........I feel fine, and am working on cool cars as usual. Ed

 

 

 

Stay safe my friends..........and "Drive it like you stole it"!

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Sweet. I will check whats on the switch circuit and suppose it wont hurt to jump the wires anyway to be sure for polarity, right?

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It won't hurt, but if it's making electricity it's polarized properly.

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