Starting/Charging intermittant problem

My daughters 1987 Wagoneer Limited 4.0L.

Seems to charge well when it is charging.

Drops all voltage occasionally as if batt is disconnected.

Jump start gets it going again, sometimes charging sometimes not..

took the alternator out and opened it up and looks nice inside and brushes are in good condition. when reinstalled, charging at 14 volts. two days ago. Dropped voltage tonight again.

so, either a bad signal wire to the Alt or a bad alt, but since the power is dropping out and batt still has 12 volts I am thinking wiring issue -possible short or loose connection at ignition?.

one thing I have noticed is the 7.5 amp fuse for the guage lighting blows regularly.

Have had the jeep for 3 years and have been upgrading items as required, but do not want to just put an alt in it without verifying it as the prob.

I have been switching between two different optima red tops that I am sure are good....same problem happens with both batteries so that is not the issue.

any comments or directions for me to look into would be appreciated.

(I have been getting some good info off this site without starting a new thread, but this time is different. This seems to be a good group)

Thanks,
Dave

You sound like you know what you are doing, but I'll through this out anyway. I would ASS U ME that all the battery connections are good and clean. What about the grounds? I think your's has one from the head to the body that is notorious for going bad. Have you cleaned all that stuff up?

yes, did all the ground cleaning couple months ago. Really helped the power windows and locks with clean grounds. I am planning on possibly adding more grounding, but not for this issue.
Thanks for the response.