Alternator issue

[grewvin1]

Merc. 5.7L 1987, mando alternator rebuilt last year. Running on the weekend have two large marine batteries on this side of the system alt. gauge droped to 10, put test unit on battery showed 50% batteries and no charging from alt. Next moring after night of shut down alt. charging? Thoughts. Is it possible for the atl. to heat up and shut down the diode which make it charge and not charge?

 

[alldodge]

Merc. 5.7L 1987, mando alternator rebuilt last year. Running on the weekend have two large marine batteries on this side of the system alt. gauge droped to 10, put test unit on battery showed 50% batteries and no charging from alt. Next moring after night of shut down alt. charging? Thoughts. Is it possible for the atl. to heat up and shut down the diode which make it charge and not charge?

It's possible for the alt to heat up and something to open up, then reconnect when cool. It does it again that is probably the case. Could also be you have a battery shorting out. Have the batts been checked individually?

 

[airshot]

Just to be sure you need to have the alternator checked by a competent alternator repairman, please do not use auto zone or murrays, instead find someone that rebuilds these things and they will have the necessary tools and knowledge to test it correctly. As ALLDODGE stated it could be a shorted battery as they can do some weird things when they short......even cause your alternator to go bad.

 

[flipbro]

Did you check the orange wire coming off the back of the alternator? Sometimes they can loosen off ! I had this happen to me mabe you will get lucky.

 

[grewvin1]

Like the orange wire idea will inspect for corrosion and make sure nut is tight, also will check the ground thanks all.

 

[grewvin1]

Like the orange wire idea will inspect for corrosion and make sure nut is tight, also will check the ground thanks all.

 

[grewvin1]

Well still having problem, checked wires on alt. all good tight and clean, checked batteries changed them for known new and good one, cleaned battery terminals. Start engine alt gauge goes to 13.5 or so then switch on blower and some lights create load alt. gauge goes down below 12. Check if alt. charging and is not, let sit for a few minutes start eng. and is charging again. Just had alt. tested a certified alt. starter rebuilder and checks out good with heavy load, alt is working. What is there in the system that may cause the alt. to not charge then after time sitting charge? Where does the purple exciter wire go to or hook in to to make the alt. switch on and off?