Elecrical problem On 1972 Duster
, Battery shows 11.7 volts , Alternator only charges at 12.5 and hardly any at idle . Shouldn't the alternator be close to 14 volts and battery at 12.6 ?
Yes, fully charged battery after surface charge, and everything off should be about 12.6, and running / charging should be no less than 13.5, no more than 14.5, and opitimal (when warm) 13.8---14.2
So basically it's not charging for whatever reason.
I would do a "quick check" to find out if the alternator is capable of charging
1...Check belt. Don't laugh. Signs of slippage? loose?
2...Do a "full field" charge test. This involves applying full battery voltage to the alternator field
The way the 72 system works, is you have two field wires. Blue is switched "ignition run" battery voltage direct to the field, this is a branch same power goes to ignition and voltage regulator
However DO NOT assume that this is "OK"
Disconnect green field wire. Jumper that alternator terminal to ground. Turn the key to "run" with engine stopped. Measure voltage at the blue wire field terminal, leaving it hooked up Should be "same as battery"
A quick check is to ground / unground your jumper wire, you should see a small spark. If you know how to measure current, "rig" your meter for current and check field current draw. Should be more than 3A, less than 5-6
Now start and run, check battery voltage. Bring RPM up slow. Battery voltage should climb right up. Keep voltage below 16 and don't rev very high until you see what it does
If battery voltage remains fairly low, move your meter to the alternator "big stud." If voltage is really high, there is a disconnect / break in charging wire path to battery. If voltage is still low, below 14-15 with engine RPM "up" then alternator is bad
