Alternator/Battery/or Serpentine Belt?

Rs2sensen · #1 02-18-2010, 11:17 AM

My fiance was recently driving my '02 Pontiac Grand Prix SE, when 6 miles from our apartment her radio went off, and then a mile or so later she lost power steering. When I got to the car, it would not turn over, and lights were faint.

I pulled the battery and it was putting out only about 350 cca, when the battery is rated for around 770. I had Advance Auto Parts charge the battery up and reinstalled it.

The battery light has flickered on twice since then, but always goes off. I'm going to pull the battery again and really clean any corrosion off perfectly, but the corrosion wasn't that bad. The battery was purchased last December.

Advance Auto Parts checked how much my alternator was putting out, and we found only about 12.5v (by testing across the battery arcs) on idle. I was told that in the high 13's was more typical. However, the tech did comment that he felt the serpentine belt was moving slowly. We brought out some of the other guys from the store, and two agreed with him, and two felt it was within a reasonable margin. The belt looks to be in good shape, and has no cracking.

The engine now starts perfectly. This engine only has 80k miles, but the vehicle has 120k (I had a crack in my block about 10k miles ago, and replaced the engine), but I believe all the original accessories were used, so it should be the original alternator.

**Normally I would think the alternator is the problem, but the loss of power steering is what really gets me. Seems like a belt issue. **

So...

1. Is my alternator going dead?
2. Does my serpentine belt need to be replaced, and because it may be slipping its not running the alternator fast enough?
3. Being in cold and wet Michigan, could it simply be a little water on the belt that is temporarily causing the problem?
4. Is it my battery?

tblake · #2 02-18-2010, 11:56 AM

Take the belt off and have a look. You may have siezed up a pulley causing the belt to slip.

GTP Dad · #3 02-19-2010, 07:48 PM

I agree with tblake but I also think that the alternator is not putting out enough. This can be due to the belt slipping but I would pull it off and have it properly tested. If it is putting out more than 13.8 volts it is good. But at 12.5it needs to be replaced.

Rs2sensen · #4 02-21-2010, 10:43 AM

Thanks guys, definitely looking more like the alternator. Car died on me last night while driving to a concert, of course I was in my suit. Traction control stayed off and wouldn't re-engage, then air bag light started flickering, then speedometer went crazy. Felt like I was going into the Bermuda triangle.

Picked up a new alternator from Rock Auto, should be here in a couple days. Thanks for the help!

GTP Dad · #5 02-22-2010, 07:44 PM

Let us know if that fixes the problem!

Rs2sensen · #6 02-25-2010, 07:31 AM

Hey guys, I got my new alternator installed...sorta. The starter clicked twice, car wouldn't start. Tried again a few minutes later, and vroom, fired right up. However, the darn belt wasn't moving so shut the engine off ASAP. I'm assuming I somehow screwed up the auto tensioner when I reset it. Seemed hard to find a balance, when it was loose enough to move freely, the belt was very loose. When it was tightened, it wouldn't move freely, but the belt wouldn't move either. Even then, the belt didn't seem that tight.

Double checked the routing and the belt is seated in the grooves of each pulley. Tried to start the engine again, this time it turned over a couple times then stopped.

Any tips?

tblake · #7 02-25-2010, 09:43 AM

Sounds like the tensioner may be shot, or there is a pulley that is siezed up causing the belt to not spin. Take the belt off and try and spin each pulley by hand.

Rs2sensen · #8 02-25-2010, 11:08 AM

I got the belt working, at least as much as when I spin the pulleys the whole belt will move. The primary problem is now electrical. No lights, locks, etc. work. So, I can't start the engine to see if the belt is truly fixed. Thanks for the replies, everyone!

Rs2sensen · #9 02-28-2010, 03:28 PM

Got her running!

New tensioner and belt did the trick. My theory is that as the tensioner went bad, it also caused strain on the alternator which in turn strained the battery. The battery likely developed an internal short, causing the short on the alternator.

I had the battery tested a couple days ago, and it was fine. This morning I retested it and the amperage was good but the voltage was low. The parts shop gave me a loaner battery to try, and the lights came on right away with that. I installed a new battery.

Thanks for the help everyone!

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