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G8 Electrical Tech Common electrical problems that go on in the G8.

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Old 08-27-2015, 08:52 AM
camerjeff's Avatar
camerjeff camerjeff is offline
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Default 2009 G8 GT Alternator FYI

We just had the Alternator fail on our 2009 GT at only 60,000 miles. Naturally it failed when I was out of town for 3 weeks and my wife was driving the car an hour away from home. She had just ran thru a couple of large puddles on the freeway she said were 4 to 6 inches deep.
The symptoms were the car went into battery conservation mode displayed on the dash, and a pitched noise started that was engine speed related. The sound was louder at higher RPM's and also when the engine was coasting with while decelerating.
I was surprised to learn the stock GT Alternator has a clutch to decouple it under light electrical loads or when not needed to top up the battery. I believe the clutch is what failed on our car.
My wife was able to make it home without incident, and her father came by to look at the car. When they restarted the car every thing was OK with the charging system, but the noise was still present. So she was able to drive the car back to work for the next week until I could get home to repair it. I ordered a new Alternator and Drive belts from Rock Auto to have them available as soon as I got home. The actual Alternator is not bad to replace, but would be a real PITA in Cold weather, or if you do not have a lift or pit available as 1 of the 3 mount bolts and the negative wire are best reached from underneath the car.
The biggest pain is that I was unable to actually remove the Alternator from the car with the power steering pump in place. But after removing the Pump and mounting bracket the Alternator can be removed easily. But don't make the same mistake I did, drain the system down by removing the Dextron VI Fluid from the reservoir before undoing the hardline. I had to clean up about 1/2 a quart of oil.
I wish I would have researched this before purchasing the Stock 6.0 part for $183, I just learned that the GXP's 6.2 Alternator does not have the clutch, and may be a more durable part, bolt into the same location, and costs around $201. I am not looking forward to replacing this part every 60,000 miles. I hope to drive this car into the ground.
So far we have been very happy with the car, the only issues had been the common lower control arm bushings (replaced under warranty) the Hazzard light switch tabs breaking the 2nd time we used them, and a left front hub failing shortly after my wife drove that side of the car into a curb this spring.
But we do have about as Basic model GT as you could buy, Cloth seats and no Sunroof.
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78 Catlina Safari, Soon to be Pontiac 400 powered
78 Sunbird Safari, Buick 231 V6 2004R
77 Astre Formula, 215 Buick V-8 T-5
73 Lemans Safari, 400 4bbl 4-speed
71 Catalina Enforcer, 455 4bbl
69 Firebird Sprint 301 OHC-6, T-5 (for Sale)
09 G8 GT, Love It!!!!!
06 Mallet Solstice #024 LS2, Now with a Tremec 6060 6-speed!
2013 F-150 Echo Boost (My local Ford Dealer SUX!!!)

Last edited by camerjeff; 08-27-2015 at 08:56 AM. Reason: Still cannot spell, or reread before posting.
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Old 08-27-2015, 06:29 PM
stellar stellar is online now
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It is possible the decoupler pulley was all that was wrong with it. The pulleys are the weak spot on that alternator and 60K is about normal for the pulley. The alternators usually hold up well. It is not a good idea to replace the decoupler pulley with a solid pulley. With the decoupler pulley the car will run smoother and the belt and tensioner will last a lot longer as well as any other bearings on that serp system.
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Old 08-31-2015, 10:31 AM
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camerjeff camerjeff is offline
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So if I understand correctly the decoupler is only in the pulley? I am planning on having the stock one repaired, I don't think there is an issue with the actual alternator as it seemed to work fine a couple of days after she ran thru the puddles, I wonder if the clutches got wet, and that is all that was wrong with it.
60,000 miles seems like a early failure mode for a modern car that is driven daily. And if the decoupler fails at 60,000 I think I would rather replace the tensioner at twice that milage, it would be easier and cheaper.
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Jeff R
78 Catlina Safari, Soon to be Pontiac 400 powered
78 Sunbird Safari, Buick 231 V6 2004R
77 Astre Formula, 215 Buick V-8 T-5
73 Lemans Safari, 400 4bbl 4-speed
71 Catalina Enforcer, 455 4bbl
69 Firebird Sprint 301 OHC-6, T-5 (for Sale)
09 G8 GT, Love It!!!!!
06 Mallet Solstice #024 LS2, Now with a Tremec 6060 6-speed!
2013 F-150 Echo Boost (My local Ford Dealer SUX!!!)
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