- Reaction score
- 554
- Thunderbird Year
- 1957
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I don't think it would keep running with no main ground. I don't think you have a generator problem, no harm in having it tested though. It's not like a small engine like an outboard motor or lawn mower with a magneto that doesn't need a battery to run.Update:
Seems generator isn’t working, I pulled the negative battery cable, and the engine immediately shuts down. This makes sense to me, guess I’ll take it out and have it rebuilt (found local place).
Thanks for advice, to tackle one issue at a time, took deep breath today. Priority, is to get it running and not draining the battery.
Thank you!
That’s interesting, I just read a post where someone did this as a diagnosis, bummer! Earlier today I cleaned the generator connections, removed dirt and rust. Well, my battery definitely doesn‘t seem to be charging during drive, starts right up initially(after recharge), if I stop anywhere, battery is weak. It’s only $125 to have it rebuilt, probably needs it anyways. Every wire under the hood, is pretty brittle, should probably replace all.I don't think it would keep running with no main ground. I don't think you have a generator problem, no harm in having it tested though. It's not like a small engine like an outboard motor or lawn mower with a magneto that doesn't need a battery to run.
I‘m doing long drives, about 90 minutes. I mentioned the 5 minute drive, because the battery totally drained after that one, I had gone on a long drive prior. Not saying it’s not the starter, but really seems like battery, maybe it’s both? After a drive, battery needs recharge, and it starts right up afterwards.If the engine was at idle when you pulled the cable, your engine speed would be too low for the generator to do its job. When the key is ON and the engine is off does the GEN light light come on? If not then that needs to be addressed.
Harbor Freight sells a volt meter for $5.00 that can be handy for troubleshooting and there is lots if info on Utube about how to test battery voltage.
I have a 55 still on 6V with an Optima battery. It has always started hot. What shape is your starter in? They are known to be problematic when they get old. Perhaps a new rebuild would help. 5 minutes of driving will NOT recharge your battery. Back when generators were common it was recommended that 20-30 minutes was needed to recharge your battery after a start.
Wow! Love this forum! Will get on this later today, and will update. I’m getting such the education from here.The charging system consists of the battery and cables, the alternator or 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 alternator 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 alternator 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 alternator isn’t recharging the battery. This could be because the alternator 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 3500 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 alternator or the voltage regulator.
doug7740
1955 Thunderbird Blue
Update:The charging system consists of the battery and cables, the alternator or 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 alternator 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 alternator 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 alternator isn’t recharging the battery. This could be because the alternator 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 3500 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 alternator or the voltage regulator.
doug7740
1955 Thunderbird Blue
It seems your generator is charging but the voltage regulator is out of adjustment. Yes the are adjustable and I believe it is covered in the shop manual.Update:
Battery was still charging according to tender. Had been charging for 12 hours.
1. Resting voltage was 6.1v
2. 6.0v with engine started
3. 5.8v with lights and blower on
4. 6.0v @3500 rpm w/lights and blower
Seems charging system is working?
I actually ordered a starter this morning (not from usual retailer), before doing this test, since price was very reasonable. Not saying this is the issue.
Thank you!
The regulator is new. Is this common, it needs adjustment? Or is it defective?It seems your generator is charging but the voltage regulator is out of adjustment. Yes the are adjustable and I believe it is covered in the shop manual.
A rebuild wouldn't be out of line. The brushes do wear out over time and simple to replace. a rebuild shop will know how to dress the commutator which the brushes ride on. That too is in the shop manual but a shop would know how to do it properly.Update:
Seems generator isn’t working, I pulled the negative battery cable, and the engine immediately shuts down. This makes sense to me, guess I’ll take it out and have it rebuilt (found local place).
Thanks for advice, to tackle one issue at a time, took deep breath today. Priority, is to get it running and not draining the battery.
Thank you!
The regulator should be set up using the procedure in the manual, assume nothingThe regulator is new. Is this common, it needs adjustment? Or is it defective?
Thanks
All these figures are on the low side or bad.Update:
Battery was still charging according to tender. Had been charging for 12 hours.
1. Resting voltage was 6.1v
2. 6.0v with engine started
3. 5.8v with lights and blower on
4. 6.0v @3500 rpm w/lights and blower
Seems charging system is working?
I actually ordered a starter this morning (not from usual retailer), before doing this test, since price was very reasonable. Not saying this is the issue.
Thank you!