I don't know what else to do...alternator not charging

Thanks Walt. I just re-ran all the tests. The alternator is wired thusly:



Test results:
H-69 #1 - ignition off, 0v Aux to ground
H-69 #2 - engine running, 0v Aux to ground, 12.5v across battery (output to ground)
H-70 #1a - VR disconnected, engine running, jumper from field to Aux, 0.5v
H-70 #1b - VR disconnected, engine running, jumper from field to Lamp (5 o'clock position), 0v
H-70 Remy - VR disconnected, engine running, jumper from field to Output, 13.5v and climbing
H-73 #1 - ignition on, engine not running, 0v Aux to ground
H-73 #2 - ignition off, Field disconnected, 2.4A Field to Output

What this tells me:
H-69 #1 - Isolation diode is not shorted (good)
H-69 #2 - Unknown -- possibly the Isolation diode is open (bad)
H-70 #1 - Alternator field is not working, fault in either stator or rectifier diodes (bad)
H-70 Remy - Isolating the field, the alternator puts out current (good)
H-73 #1 - The amp light circuit is bad (bad)
H-73 #2 - Field circuit is good (good)

Tests 69 & 70 tell me the alternator field circuit is bad, but test H-73 #2 counters that -- ??

Test H-73 #1 tells me I need to check my amp light circuit before I put any new components in, like a new alternator or VR.

I'm now 90% sure the alternator is bad, as I checked the wiring and it's all correct. But I will check the wiring one more time just to be certain.

Does this now make sense?

Regards,
Tim

 

I'm on my third VR, simply because the tests, recommended by Remy, were indicating that. With the correct tests, it now appears the Alternator is in fact the culprit.

Also, I did move the white wire to the 5 o'clock position.

I am now considering reinstalling the original alternator as the original VR may have been the culprit. And of course re-running all the tests.

I'm getting good at R&R alternators...

Regards,
Tim

 

The aux terminal will not have any voltage until the alternator is charging. The wire from the charge light going to the aux terminal should give the Aux terminal enough power to excite the system for it's initial start. If this does not happen then the alternator field circuit will not be energized. Voltage regulator connected of course.

 

Hmm, so does this mean I've got a problem with my amp light circuit or the field? Sorry for being thick.

Regards,
Tim

 

See post #21. In the photo I showed how I wired per Walt's suggestion. This is closer to original.

Regards,
Tim

 

TBH, I'm not quite sure either. It does seem logical that some sort of current should flow through the 5 o'clock lug. That's the isolation diodes and otherwise there's nothing. However, on the 55 amp alternator nothing is connected there.

Regards,
Tim

 

Good news!

I re-installed the original alternator with the new VR. Everything works, all tests passed and amp light goes out quickly.

Thanks for for all the help, I'm much smarter on the charging circuit now!

Regards,
Tim

 

Yep the Aux circuit in the new alternator is bad...

 

Excellent Tim. Why I never toss out any old stuff until it is proven as trash. Plus, knowledge is a good thing.