Alternator Question

Fishthatkills,

As stated above, the field terminal marked "ground" must electrically connect to engine ground. If not, no field current can flow and the alternator will not output current. Reasons why it might not get grounded:
1) Corrosion at interface between the brush copper to the alternator frame or corrosion from the alternator frame to the engine.
2) You have a later style brush installed for the "ground" one (70's square-back alt). I recall they can interchange. The later ones are isolated from the frame. See above to fix.

Things to check (engine running):
1. Whenever there is ~12 V ACROSS the field terminals, the alternator should put out full current (~30 A).
2. If not, verify there is ~12 V from the "Field" terminal to battery ground.
3. If not, the problem is in your voltage regulator, assuming your battery is low and needs charging current.
4. If OK, verify you have <1 V from the "ground" terminal to battery ground. If not, turn off the engine and locate the main resistance using your DMM - terminal to alt frame, alt frame to engine, engine to battery gnd.
5. With above understanding, you can manually actuate the alternator by applying voltages to the field terminals.
6. To measure alt output, use your dashboard ammeter "ALT". If broken (resistance >1 ohm), bypass with a wire at the firewall connector on engine side (larger bolted terminals). You will then be flying blind on alternator output, just like most cars since 1982.

Good luck. Re-read everything in posts above. Buy a DMM if you don't have one. Learn how to make simple electrical measurements and understand the difference between voltage drop and current flow. Wikipedia is a good start.