87 b2 alternator not charging

[68cougar]

Ok so my 87 b2 alternator stopped charging. not putting anything out just battery voltage. I have 12 volts when key off on both main black wires and yellow wire on reguator. key on there is voltage on the green regulator wire, but still not charging, i can full field the regulator and it will jump to 14.5 or higher thats just where i removed my jumper. The amp meter in the guages does not move. Am i correct in saying that if the amp meter is junk the alt will not charge? Can i use this harness(picture) to rewire the alt to bypass the amp meter to get alt to work? My harness does not have the white wire connecting the pigtails and to my understanding that wire is not there if you have an amp guage.

 

[68cougar]

I want to add that i have tried a different alternator and same results. Both alts could be bad i guess but ya never know. I have not taken to autozone to have alt checked.

 

[RonD]

These can be helpful for wiring tests:
http://www.therangerstation.com/tech_library/EDiagrams/index.htm

Yes the wire from the amp meter "turns on" the alternator, by "full fielding" you are doing what that wire and the regulator should be doing, setting the output voltage of the alternator.

The 14.5v means the fields and rotor are working, the fields get "power" to send to the battery from the rotor spinning, the rotor is a spinning electro-magnet.
The regulator supplies power to the rotors brushes, from 5v to 10v, the higher the rotor's voltage(stronger magnet) the more power the fields put out.

Measure the voltage on that wire with key on engine off, if it's at battery level then regulator could be bad, but on two alternators????

 

[68cougar]

tossed a new regulator at it since they are cheap....normal charging now. thanks rond

 

[Spede Demn]

Just an fyi to add for quick easy testing of alternators... place a small wrench or metal object against the back/center of the alternator, if its working the magnetic field will hold the wrench in place.

 

[PetesPonies]

The AMP gauge has nothing to do with the alternator charging, it's a shunt type of gauge.