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Pontiac Sunfire alternator problems

We have a Pontiac Sunfire (95) and have been experiencing alternator problems since we purchased the vehicle a few years ago.

The first time it went the original seller agreed to replace the alternator for free but commented that he felt it was the stereo system that caused the failure.

Since that time we have replaced it 3 more times and each time it failed within 10 months.

The most recent failure (today) happened within 5 months.

Last summer we took it in for a service diagnostic and the results came back as, no abnormal current drain, good battery, drive belts ok, no bearing problems, etc. In other words the service guy could find no obvious problems that were causing alternator failure.

What he did say was that auto parts now days are made so cheap that it’s possible that our problem is because of that.

I figure once or twice is a possibility but 4 times? No way!

Sooooo, I ask, anyone have some suggestions? (besides blowing up the car)

Just out of curiousity, is the stereo system a high output unit that uses a large capacitor (in the Farads range) on the power feed? Also ask the service diagnostic technician if he did a post mortem on a dead alternator to figure what failed. He/she might be able to visually tell if the failed component was previously replaced. Let us know.

The following is the result of studying alternator design. The current limit of an alternator is set by the design of the windings and that the load will be resistive. However, I have seen no information about how an alternator reacts to a load with a leading power factor, i.e. capactive/resistive load. The original seller may be correct that the stereo system may be causing the failures. JMHO.

Hope that helps. Get back to us with ‘more’.

It is a high end stereo system but without a capacitor. After the last alternator replacement I stopped using the stereo to see if that might be the issue. So it would seem the stereo is not the culprit.
I did not get a report on the dead alternator. I’ll ask this time though. - Paul

Turning the stereo off will not prove anything. Removing it entirely might, but I am not recommending that. Something I always used to do with my cars was to check the ground wire between somewhere on the engine that connects to the body. It probably won’t help you, but in the 70’s through the 80’s I ran into the problem many times.
My 72 Cadillac wasn’t fully charging the battery. The power windows were sloooow. The big ground strap was completely burned off by the exhaust pipe. Why they put it there I will never know. I forgot to reconnect it on a 74 Suburban and my wipers wouldn’t work. Reconnect and they did. My 76 Impala ALT light used to come on during a trip: I put an extra ground on the engine and the light stayed out for another fifteen months, then I changed the brushes and fixed the problem. Two Toyotas wouldn’t always crank, but they did when I scraped the paint off the firewall and reconnected the wire. If only your problem could be that easy.

Does the car idle for prolonged periods? If it does, and there are several high amperage things turned on, that could be over-loading the alternator.
Here is a Service Bulletin :Number 02-06-03-008C , which deals with this problem.
Heavy current users are electric motors, such as: electric air pump (for emissions control); blower motors. Also, electric heaters and lights: rear window defogger; head lamps. These items draw 20 to 25 amps EACH.
You need an electrician to check the field control circuit from the engine computer (ECM), and the amperage draw of each, and all, electrical devices…at idle, and at raised engine rpm

Does the car idle for prolonged periods?
Not really, we live in a very small town with three stop lights, so idle time is less than a minute most times…maybe 2 or 3 max but not very often.
Heavy current users are electric motors, such as…
The car is a very basic model. No AC, power windows, seats, etc.
Every time the the alternator has died it has been in the summer (except now) so things like rear de-fog and blower are not used. As mentioned we don’t have AC so that doesn’t add to the demand either.

As a foot note, when we took the car in today I expressed my disbelief and concern of 4 alternators dieing within 2 years and the mechanic responded that he’s not surprised at all. He said he had one customer who has gone through 5 in a two year period.
He really thinks QC on parts has gone to zero because of out source manufacturing and cost control. - Paul