1957 Thunderbird Charging System

1

1967 Camaro

Member
What voltage should I read at the battery with the engine running? I've measured voltage on other vehicles (12V Systems), and the voltage at the battery is usually around 13-14 vdc. I am reading just less than 12 volts on the Thunderbird with the engine running.
 
Both my 1959 Chilton's Manual and 1967 Chilton's say 15.0 volts for the regulator setting. So you have a non-working charging system. Either generator or regulator or broken wires.
A fully charged 12 V. battery will read 12.6 volts (2.1 per cell) so you obviously need over that to charge it. I'd say 13.8 at the very least.
 
I agree with 40, but I think with a generator (as opposed to an alternator) you measure the "set" voltage above idle speed. 1500rpm IIRC. Someone will correct me if I'm off.
 
As mentioned, you should measure voltage on a generator equipped car above 1500 RPM as generators do not produce full voltage below that. reading should be in the 13.7 to 14.5 range

If all of sudden the voltage has dropped, I would have the generator checked out - also the regulator
 
I thought I'd jump in here because this is still fresh in my mind having recently went through the generator - fwiw. First thing I'd recommend that adjusting the regulator output is pretty far down the list. If the output is below spec or not charging there are other diagnostics to perform first. The Shop Manual is your friend here because while the tests are simple and generators are tough, the voltage regulators can be damaged by the wrong connections. Be sure to follow Ford or "Type B" generator testing procedure. The most common problem is the brushes, they oftentimes will not make good contact with the commutator, by getting hung up in the holders. They will have an air space between that isn't visible but enough to prevent good current transfer. Try jamming them tight against commutator while at idle. They should probably be inspected for evidence of burning etc. A "full field" test is another. Remove all wires from generator itself. Jumper ARM to FLD. Start engine and check voltage from ARM to GND. Only perform this test long enough to verify voltage is present.

Generators need good ground and connections just like alternators, turn the lights on and heater blower to load up the system and run idle at 1500 to 2000 RPM. The charge tables show that generator systems run hotter than alternator systems by quite a bit. But I would not adjust a regulator until other more likely issues are eliminated - poor grounds and corroded cables for example. Adjustment is a little tricky and voltage/current/cutout set points should already be very close. Hope this helps.
 
Measuring at the battery (post to post) gives you the battery voltage, should be close to 12v.

On generator equipped cars, 13.8 to 14.1v is about normal. Alternator cars I like to see 14.1 to 14.5v. This is measured through the generator or alternator, not at the battery.
 
Well actually no, battery voltage should be closer to 13 volts, not 12. In fact a battery that has been recently charged will show over 13 volts, called a surface charge. Generator set point charging voltage is higher than an alternator at any given temperature, at least according to the shop manual. This may be due to a generator having more of a "choppy" or averaging waveform? Not sure on why exactly.

The voltage regulator throttles back both voltage and current mechanically via points, they are somewhat finicky and adjustments have to be done with a good understanding of how they work. High resistance in cables and grounds should be remedied before messing with regulator output. Any corrosion will limit current output.
 

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