Ignition Control Module problem
1....JUST like the ECU, the regulator MUST be grounded.
2...Easy check find the green wire at the alternator. Use a "clip lead" and connect the alternator field terminal you just exposed to ground. Start and see if it charges
If not, measure voltage at (connected) blue field terminal, key on. Should be "same as battery." If so, take your meter, set to "high amps" (10 or 20A scale). Disconnect your clip lead and hook the meter ("on amps) from the alternator field terminal to ground. It should read more than 3A less than 6A. this is field current draw
3...If that is OK, hook your clip lead back up. If you happen to be in subdued light, you can connect/ disconnect it a couple of times and look for a spark just to be sure
Now with blue field hooked up "normal" and the other field terminal still clipped to ground, again start and run engine, bring up RPM. CONFIRM voltage is still low, perhaps below 12V
4...Now move your meter to the alternator output stud. If it was quite low at battery, but way high (over 16V) at the alternator, you have a problem in the "charging line" the wire from the alternator to the battery.
If both points are still low, below 12 (charging should actually be much higher) then that alternator is bad
Here's a simplified diagram of the 70/ later charging system. These are INcorrectly called "dual field" They are CORRECTLY named "isolated field
Here is basically what you have
12V for the field and regulator power is fed directly ( blue) to either field terminal, and to the "I" (Ign) terminal of the VR This "I" terminal is also the "sensing" terminal for the VR
The "F" VR terminal goes to the remaining alternator field terminal, and controls "the amount of ground" on the field
Both VR and alternator MUST be grounded MUST
Output of alternator (factory) meanders through bulkhead terminal, ammeter, welded splice, BACK out bulkhead terminal, and to battery.
1....JUST like the ECU, the regulator MUST be grounded.
2...Easy check find the green wire at the alternator. Use a "clip lead" and connect the alternator field terminal you just exposed to ground. Start and see if it charges
If not, measure voltage at (connected) blue field terminal, key on. Should be "same as battery." If so, take your meter, set to "high amps" (10 or 20A scale). Disconnect your clip lead and hook the meter ("on amps) from the alternator field terminal to ground. It should read more than 3A less than 6A. this is field current draw
3...If that is OK, hook your clip lead back up. If you happen to be in subdued light, you can connect/ disconnect it a couple of times and look for a spark just to be sure
Now with blue field hooked up "normal" and the other field terminal still clipped to ground, again start and run engine, bring up RPM. CONFIRM voltage is still low, perhaps below 12V
4...Now move your meter to the alternator output stud. If it was quite low at battery, but way high (over 16V) at the alternator, you have a problem in the "charging line" the wire from the alternator to the battery.
If both points are still low, below 12 (charging should actually be much higher) then that alternator is bad
Here's a simplified diagram of the 70/ later charging system. These are INcorrectly called "dual field" They are CORRECTLY named "isolated field
Here is basically what you have
12V for the field and regulator power is fed directly ( blue) to either field terminal, and to the "I" (Ign) terminal of the VR This "I" terminal is also the "sensing" terminal for the VR
The "F" VR terminal goes to the remaining alternator field terminal, and controls "the amount of ground" on the field
Both VR and alternator MUST be grounded MUST
Output of alternator (factory) meanders through bulkhead terminal, ammeter, welded splice, BACK out bulkhead terminal, and to battery.
