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...either that or it's haunted! Speakers turn on and off, instrument lights and headlights flash, doors lock and unlock repeatedly by themselves, and clock resets to 12:00 periodically.

Alternator maybe?

Any ideas?

my 07 was doing the same thing clean the battery cables sounds crazy but that caused it

stevea wrote:my 07 was doing the same thing clean the battery cables sounds crazy but that caused it

I've checked the cables and they look like they're brand new. No corrosion or anything else apparent. Clean them anyway?

My speakers are cutting in and out on my '07. I just thought it was the speakers but might be the same problem.

I bought mine used. It was a lease vehicle and has been back through GMC to clean it up for the retail market. Most things are clean and pristine like the battery and cables. It came from up north though and has a little rust on the frame from salt. I'm wondering if there could be a ground strap rusted through somewhere that is causing it.

mine looked clean too they had glazed over around post and not making good connection i would clean them

Could be bad battery. Negative pole may be a little busted internally causing loss of ground

stevea wrote:my 07 was doing the same thing clean the battery cables sounds crazy but that caused it

My son's 08 did the same thing...battery cables were replaced never did it again.

Among other more complicated things I hear it could be caused by corrosion on the pigtail adapter, battery terminal, and/or loose, broken or corroded ground straps.

Battery checks out, I cleaned the terminals and wires, cleaned the pigtail adapter connections, and checked the ground straps last night. We'll see what happens.

Thanks for the input.

Damm GMC and Chevrolet. Y'all can have em

Got an 04 doing same thing except battery light comes on no ac heat or gauges replace alternator battery everything cleaned and connected have no idea hit a bump and starts working for a cpl hrs then goes out again

drake09 wrote:hit a bump and starts working for a cpl hrs then goes out again

That is an excellent indication it's a wiring issue somewhere, might be a nightmare to find. I'd start with ground wires in obvious places and go from there.

Had one years ago do that. The short itself turned out to be internal in the radio....making everything else go crazy

Yea I've cleaned all the grounds from front bumper to tail lights and still not working