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Alternator problems

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Peter Pan

New member
I have changed my regulator on one of my alternators, three times in 2 months! At first, the system works fine for 2 or 3 weeks (6-10 hours of actual operation) and then the voltage displayed on my gauge goes from 14.2 volts to 17.5 volts. It stays there for a couple minutes and then the voltage drops to battery voltage and starts loosing power.
Any ideas?:confused:
 
A loose or bad ground can cause that. Check your battery terminals. Check the resistence between the regulator ground and the battery ground - it sould be nearly zero.
 
Peter - the problem may be difficult to locate. I think the regulator may depend on it's contact with the alternator to supply the ground. Be sure that the mating surfaces are clean, tight, and free of grease. Same goes for the ground wire at the battery and the connections at the alternator. In other words, check each and every connection between the battery, the alternator, and the regulator. If all that fails, pull the alternator and have it checked at an automotive rebuild shop.
 
Got it.
Both alternators (I have 2 CAT C-12 engines) worked flawlessly for the first 2 years, then I noticed that one alternator wasn't working so I sent it to a shop to have it checked and they returned it saying that they had changed the voltage regulator. I re installed the alternator and didn't work at all so I started looking at the positive wire coming out and noticed that it had a circuit breaker, I reset it and worked fine for 10 hours. Then the voltage coming out of this alternator went up to 17.4 volts for 2 or 4 minutes and dropped dead. I sent it back to the shop and they told me they would install a new "heavy duty" voltage regulator. I re installed it and worked fine for 15 hours before the same thing happened. Last time it only worked for some 3 or 4 hours before going dead.
I will check the negative circuit,as you kindly mention, since I have not done that at all.
 
Are you running both alternators charging the same battery bank. I had the same problem charging the same battery's together so I invested in a Balmar system that is built to work together. $2500. ouch but now I hardly ever use my generator.
 
Hordos, I will look into this Balmar system that you mention, but my alternators charge independent battery banks. The generator also feeds a battery charger that maintains all 3 batteries charged at all times.
Being very hot down here I need my A/C working all the time so I cannot afford to have my generator off.
Thank for your kind reply.
Peter
 
Chawk, you are the man!! You were 100% on the money. The problem was indeed hard to find since a loose contact in one of the regulator wires was the problem. The thing was that the screw was tight, but the connection was loose and since the screw had plastic over it to avoid grounding that wire, it didn't make contact with the regulator.
Thanks a bunch for a problem that was killing me. Al ground contacts are now nice and clean and the alternator puts out an even 14.2 volts at first, slowly dropping to 13.9 after an hour or so.
Peter
 
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