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Trying to keep this as short as possible. Had an alternator installed by Pepboys in 2014 which died 2 weeks ago. I took it out and they replaced it under warranty. I installed it myself which was very easy on the Forester. The voltage of the 3 month old battery was 12.4, we had to jump start it. And everything worked fine for 4 days. Then the battery and brake light on the dash started to flicker so I checked the voltage on the battery. It was fine when the car was just idle but when driving even at low RPM the voltage at the battery exceeded 15V, even went to 16V at higher RPM.
I took out the alternator and Pepboys replaced it again under warranty. They tested the unit in the store and it seemed fine but I don’t think their test equipment is simulating higher RPM (Again it was fine when just idle). I also noticed that the copper wiring of the alternator turned black which means it overheated. It still worked but it seems that the Voltage regulator got fried. I am pretty sure that the alternator wiring from 2014 was not black like this one (part # 11058, 90 amp).Now with the 2nd alternator replacement we drove for about 12 miles one way to a store. Popped the hood and looked if the alternator wiring is starting to turn black again, and it did a little. So now we are worried that the same would happen again. Especially when driving longer distances with the AC or heat running.
The voltage at the battery is stable at about 14.3 to 14.5V under load. The battery was reading 12.65V before I installed the second alternator. We also had the battery tested by Advance Auto before the 2nd alternator was installed. I also performed a voltage drop test, and the ground of the alternator housing passed as well.
I noticed that one of the brake lights in the back burnt out but that doesn’t necessarily mean anything. It could have happened a long time ago.I checked the wiring as much I could, sanded and cleaned the connectors to the battery. The connectors that go to the alternator seem fine too. Any ideas what could cause the alternator to overheat? I am wondering if it is always running at 100% and something is not telling it to chill. I am sure that the belt has the right tension as the tensioning screw was marked. Plus I can turn the belt by 90 degrees on its longest run with two fingers.
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Most standard alternators output a max of 15V at speed.
Above that, your looking at cooking your battery and possibly your electrical system.I’ve experienced aftermarket alternators having common failures.
Appears that is what your experiencing.
My suggestion would be to purchase a quality name brand unit and see if you get the same results.Agreed. I worked at Pep Boys for about 3 months and over the last 2 years or so the company they use to rebuild alternators has gone downhill badly. Have seen about 10 alternators from Pep Boys overheat and be returned and exchanged under warranty. I would recommend looking at Rockauto.com for the next replacement. The last alternator I got from Orielly’s also shared this problem.
Interesting about those pep boys alternators. The 2nd alternator that I installed on Saturday is still looking ok for now. I didn’t see any new copper wires that turned black. On a 15 minute drive, half of it highway we turned the lights on , AC and radio. Afterwards I checked the temperatures of the alternator with an Infrared Thermometer and the highest reading I got was 130F, so that is somewhat comforting for now. Will have to check again after a longer drive. On my Outback I got a reading of 150F but that was after driving for much longer. (The Forester is my girlfriends car)
So far the alternator is still working. After 1h drive the temperature of the alternator casing was 132F, the copper wiring measured from the top 150F and measured on the side 180F. Temperature outside on that day was about 55-60F. It seems it is still within normal range. Hopefully it was just the alternator that was bad and nothing else that caused it to die. I read in several forums that some people had to replace their alternator up to 3-4 times
If it will die again within a few weeks I will comment again.
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