1957 generator testing

[Ames]

Hey all, I have been up and running for about a year now but now I'm having charging issues. I think that I've had them awhile but my battery finally couldn't take it anymore. I'm trying to find the correct way to find out if my generator is working properly. I polarized the regulator by jumping FLD terminal to BAT terminal and I got a spark. When the car is running at about 1500 rpm the battery only tests out at 12.45 volts. Should it be more?

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[57tbird57]

easiest way to find out if its charging, with the car running, disconnect the ground cable from the battery. if the car stays running, then the generator is charging

 

[doug7740]

The charging system consists of the battery and cables, the generator and an external voltage regulator. The function of the battery is to spin the starter motor to start the engine. Once that’s done the generator takes over, satisfying the car’s electrical demands and keeping the battery charged. The battery then acts primarily as a filter, keeping voltage spikes from damaging the car’s electronics. The voltage regulator rapidly switches the alternator in and out of the charging circuit to provide the car with the correct voltage.

In 1955, the electrical system of the Thunderbird was 6 volt positive ground. In 1956, the Thunderbird electrical system was changed to 12 volt negative ground. On the 12 volt system there are two important numbers to remember, they are 12.6 volts and 13.5 volts.

12.6 Volts: If you think your car has a 12 volt battery, it doesn’t. The 12 volt battery actually has six individual 2.1 volt cells (one under each fill cap). Thus, when fully charged, the battery should have a resting voltage of 12.6 volts. If with the engine off, the resting voltage is less than 12.6 volts, the battery is low and needs to be recharged. Of course, it begs the question of why the battery is low. It could be that the generator isn’t working, or that the battery has reached the end of its useful life.

13.5 Volts: With the engine running, the alternator should output a charging voltage that’s about a volt higher than the resting voltage, or about 13.5 volts. The exact charging voltage may be as low as 13.2 volts or as high as 14.2 volts.

If your Thunderbird is a 1955, with a 6 volt, positive ground system, the resting voltage is 6.3 volts and the charging voltage should be about 7.1 volts. The exact charging voltage may be as low as 6.6 volts or as high as 7.1 volts.

Take a multi-meter and set it to measure DC voltage, then measure the voltage across the positive and negative battery terminals with the engine off. On a 12 volt system, a fully charged battery should read a resting voltage of 12.6 volts. After you start the car you should see a charging voltage of about a volt higher than resting voltage. If the reading doesn’t increase by about a volt or if it stays at the resting voltage, it means that the generator isn’t recharging the battery. This could be because the generator is defective, the regulator is defective, or the wiring between them has failed. In any case, if you drive the car, the battery will run down. If the battery runs down enough that the ignition stops firing, the engine will stall. It’s really important that you don’t simply jump-start a car with a dead battery without checking to see if the alternator is charging.

A basic charging system health test: Use a multi-meter to measure the resting and charging voltages as described above. Then, with the engine running, gradually increase the electrical load by turning on the headlights and the blower fan. Then increase the engine RPM to about 3,500 as you watch the reading on the multi-meter. If the voltage stays about a volt higher than resting voltage, then the car’s charging system is functioning. But if the voltage drops or increases dramatically at any point, there’s a problem with the generator or the voltage regulator.

doug7740
1955 Thunderbird Blue

 

[Ames]

The charging system consists of the battery and cables, the generator and an external voltage regulator. The function of the battery is to spin the starter motor to start the engine. Once that’s done the generator takes over, satisfying the car’s electrical demands and keeping the battery charged. The battery then acts primarily as a filter, keeping voltage spikes from damaging the car’s electronics. The voltage regulator rapidly switches the alternator in and out of the charging circuit to provide the car with the correct voltage.

In 1955, the electrical system of the Thunderbird was 6 volt positive ground. In 1956, the Thunderbird electrical system was changed to 12 volt negative ground. On the 12 volt system there are two important numbers to remember, they are 12.6 volts and 13.5 volts.

12.6 Volts: If you think your car has a 12 volt battery, it doesn’t. The 12 volt battery actually has six individual 2.1 volt cells (one under each fill cap). Thus, when fully charged, the battery should have a resting voltage of 12.6 volts. If with the engine off, the resting voltage is less than 12.6 volts, the battery is low and needs to be recharged. Of course, it begs the question of why the battery is low. It could be that the generator isn’t working, or that the battery has reached the end of its useful life.

13.5 Volts: With the engine running, the alternator should output a charging voltage that’s about a volt higher than the resting voltage, or about 13.5 volts. The exact charging voltage may be as low as 13.2 volts or as high as 14.2 volts.

If your Thunderbird is a 1955, with a 6 volt, positive ground system, the resting voltage is 6.3 volts and the charging voltage should be about 7.1 volts. The exact charging voltage may be as low as 6.6 volts or as high as 7.1 volts.

Take a multi-meter and set it to measure DC voltage, then measure the voltage across the positive and negative battery terminals with the engine off. On a 12 volt system, a fully charged battery should read a resting voltage of 12.6 volts. After you start the car you should see a charging voltage of about a volt higher than resting voltage. If the reading doesn’t increase by about a volt or if it stays at the resting voltage, it means that the generator isn’t recharging the battery. This could be because the generator is defective, the regulator is defective, or the wiring between them has failed. In any case, if you drive the car, the battery will run down. If the battery runs down enough that the ignition stops firing, the engine will stall. It’s really important that you don’t simply jump-start a car with a dead battery without checking to see if the alternator is charging.

A basic charging system health test: Use a multi-meter to measure the resting and charging voltages as described above. Then, with the engine running, gradually increase the electrical load by turning on the headlights and the blower fan. Then increase the engine RPM to about 3,500 as you watch the reading on the multi-meter. If the voltage stays about a volt higher than resting voltage, then the car’s charging system is functioning. But if the voltage drops or increases dramatically at any point, there’s a problem with the generator or the voltage regulator.

doug7740
1955 Thunderbird Blue

Excellent response, thank you. Whats your opinion about using a standard battery off the shelf versus the original?

 

[doug7740]

Ames,

I would have no problem using a standard battery, as long as it is the correct rating and size for your Thunderbird.

Currently, I have a 6 volt Optima battery with a cloaking device in my Thunderbird.

doug7740
1955 Thunderbird Blue

 

[Ames]

I will check that out, thanks.

I checked it out, as soon as I pulled the cable off the post she quit. Now what, regulator first? I had the brushes and bearings replaced in the generator about a year ago.

 

[57tbird57]

Great help, by the way, what is the official color of your Bird? AND, I replied back to 57tbird57 about the car quitting when I pulled off the negative cable, what do you think?

if the car stalled after removing cable, i would say the generator is not charging or not charging enough

 

[57tbird57]

if the car stalled after removing cable, i would say the generator is not charging or not charging enough

you could put a new set of brushes in it and solve your problem cheap

 

[Ames]

you could put a new set of brushes in it and solve your problem cheap

Thanks 57 for the advice, I'm leaning towards the voltage regulator because of the amount of time I ran the car without polarizing the generator and the few hundred miles that are on the new brushes. I appreciate ya'lls help on this.

 

[fordrodsteven]

Why don't you verify whether or not the generator is producing any voltage / amperage before deciding the problem is your regulator?

 

[Ames]

Why don't you verify whether or not the generator is producing any voltage / amperage before deciding the problem is your regulator?

I'd love too but I'm not smart enough yet. I've been trying to find procedures to test but can't find anything specific to the Bird. I've seen instructions to use DF and F posts for vintage British cars but I have three, G post and F post on the outside of the generator and a third post that connects the battery to the back of the generator. I don't want to just start touching posts with my voltmeter and cook something. I guess I'm not even sure that I am polarizing the generator correctly either. Any guidance would be appreciated.

 

[fordrodsteven]

Try this information from one of my old Motor's manuals.

 

[Robert Evans]

Hey all, I have been up and running for about a year now but now I'm having charging issues. I think that I've had them awhile but my battery finally couldn't take it anymore. I'm trying to find the correct way to find out if my generator is working properly. I polarized the regulator by jumping FLD terminal to BAT terminal and I got a spark. When the car is running at about 1500 rpm the battery only tests out at 12.45 volts. Should it be more?

If you switch on the lights and the wipers the voltage should increase. This is what the regulator is ment to do. You may need to replace or adjust your regulator if you can. 12.45 volts is only just about the volt for running the engine.

 

[Ward 57]

Ok I pulled the cover off the regulator to paint it black and put on the proper decal. Checked all the points and when I pushed on the batt points I saw a small spark. I forgot I didn't disconnect the battery first. Now when I start it the gen light stays on but dims a little when I rev it up. What did I screw up and how to fix it.?

 

[paul5456]

Pull the generator and regulator and bring it to a auto electric shop if you have one nearby

 

[Ward 57]

The generator and regulator have been working perfectly I know they are fine, I think I just screwed up the polarization of the generator.

 

[Ward 57]

Try this information from one of my old Motor's manuals.
View attachment 4019 View attachment 4019 View attachment 4020 View attachment 4019 View attachment 4020

OK I'm getting two stories here on how to polarize the generator. The method above to ground the field terminal and a hot jumper to the armature. In the shop manual it says to disconnect both and briefly connect them together. I tool the cover off to paint it and accidentally connected the batt points and now my light won't go out when running.

 

[Ward 57]

OK I'm getting two stories here on how to polarize the generator. The method above to ground the field terminal and a hot jumper to the armature. In the shop manual it says to disconnect both and briefly connect them together. I tool the cover off to paint it and accidentally connected the batt points and now my light won't go out when running.

Polarized using the shop manual instructions and now it works properly again.

 

[cscolastico]

Ok I pulled the cover off the regulator to paint it black and put on the proper decal. Checked all the points and when I pushed on the batt points I saw a small spark. I forgot I didn't disconnect the battery first. Now when I start it the gen light stays on but dims a little when I rev it up. What did I screw up and how to fix it.?

It's possible that you knocked the voltage limiter on the regulator out of adjustment. I replace my regulator three times because the new ones were charging either to high or two low. I noticed that my voltage climbs from about 12.8 -13.0 before startup, but takes a couple minutes to get to 13.5ish. The longer I run the car (hotter) the voltage gauge slowly rises to 14.5 -14.8 volts.

BTW, I fiddled with adjusting voltage limiter for quite a while, before getting it right. it's a bit sensitive.

 

[jimntempe]

It's normal for the voltage to rise as the battery gets charged up. I believe the primary control is to limit current so a somewhat discharged battery might only need to have 12.9 volts applied get the max current feed. As it gets more fully charged it's voltage rises and consequently the voltage needed to further charge it is higher.