Alternator Problems

[GSJoe]

My friend Matt just called me while on his way back home to Charlotte from a trip to Greenville, SC. The alternator on his '91 ZR-1 has just died, and he's concerned about making it back home. A bigger concern, however, is the fact that this is about the fifth time he's had to replace the alternator in that car in the past two years! Has anyone else experienced an alternator issue like this or does anyone have any knowledge as to why he's having this problem?

[VetteVet]

Without knowing what the failures were, it's hard to say.

I can speak from personal experience, that some of the aftermarket replacement alternators have substantially smaller pulleys on them. That smaller size, combined with the free-revving LT5 makes these alternators spin to the moon and fail in short order if you like to wind your motor up(and who doesn't like to wind up an LT5?)

If Matt's been having bearing or brush/commutator failures, that may be his problem.

Jep

[Marc Haibeck]

Jep has a good point. Always transfer the original pulley to a remanufactured unit if the pulley on the reman unit is smaller.

I have noticed a pattern. It seems that cars that are driven often are less likely to have an alternator problem than low mileage cars that are stored a lot. I believe that the alternator can be damaged from excessive heat if it is used to charge a dead battery. It was not designed for high current output for long periods of time. It was designed to charge the battery between starts and counter the accessory power use.

If the car sits for more than two weeks, a Battery Tender should be used. If a battery maintainer can't be used, the battery should be disconnected and charged before starting the car. I think that a ZR-1 should be jump stared only in an emergency.

Note that the alternator on the LT5 is enclosed in a hot environment under the plenum. On most other cars it is in the open with plenty of air flow over it.

Also, a weak battery makes the alternator work harder because it needs more charging. Keep the battery fresh. They cost much less and are easier to access than an alternator.

[LGAFF]

mine croaked on the 92 this winter; less than 2 years old and less than 400 miles on it...I did swap the pulley; and the battery did croak once and was brought back

[XfireZ51]

I've been running a set of under drive pulleys for the last 4 years. But I drive my car more than 3k miles/yr AND I disconnect the battery during the winter. I did just replace the battery this winter.

[scottfab]

Something that has not been mentioned (but has come up before over the years) is that some auto parts houses will try to unload their smaller units on you. I think the standard C4 is a 105 amp unit and ours is a 120 amp. I ran into this so I simply bought a rebuild kit and kept the original 120 amp diode pack that came in the original one.

The link to the rebuild is on TechNet at:
http://www.zr1netregistry.com/Inform...r-Rebuild.aspx

Another difference between alternators is that ours has a threaded mount hole on the back for the stock mini bracket that mounts to the head. The smaller non ZR-1 units don't have this hole and therefore the bracket is useless. I suppose the good news is that without that bracket you can remove the alternator without removing the plenum. There is a TechNet article on that too.

[GSJoe]

Thanks for all your thoughts and suggestions, guys. Matt did make it back home late yesterday, and his ZR-1 is safely tucked in the garage at the moment. Sometime this week he intends to pull the plenum to replace the positive battery cable to the starter. Of course he will have to get another alternator, but I'll suggest we take his broken one apart to try to determine what happened to it. His Optima battery has been questionable for some time now, so I plan to suggest its replacement with a new Interstate battery--the big, heavy-duty, correct one for the ZR-1. I bought one of those for my ZR-1 last year and it's been great. Does anyone have a suggestion as to where to buy the best alternator currently available? I know Matt has used several sources in the past, but every one he's bought has been less than reliable for him. Thanks again for your help with this issue.

[A26B]

REMY rebuilds alternators & starters for virtually all of the major auto parts distributors, Autozone-Duraguard, AC Delco-AC-Delco, Advance-ProForm, OReilly-Ultima, etc. The electronics in the core are tested and if good, will remain as-is in the rebuild. They leave Remy in the customers brand boxes.

Simply put, this means that an alternator core may only be cleaned, inspected and receive new bearings and brushes before going out the door to be sold as "rebuilt." Consequently, the voltage regulator, rectifier, rotor, stator & wiring may not be replaced at all. The ACDelco units that were sold by GM were 100% rebuilds. I'm not sure about the ACDelco units of today.

I recommend buying a 100% new parts rebuild, 124A alternator.

[AT T 2D]

Could it have something to do with the two large amplifiers he has for the audio system? I would think they put quite a load on the alternator, he does like his music loud.

David

[VetteVet]

Originally Posted by AT T 2D

Could it have something to do with the two large amplifiers he has for the audio system? I would think they put quite a load on the alternator, he does like his music loud.

David

I wan't aware that he had a mondo sound system. That could definitely have a bearing(pun intended) on alternator life.

Jep