Question about Chevrolet Suburban 1500

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Charging problem on 2005 Suburban - gradual voltage reduction

The battery in my 2005 Suburban (45,000 miles and fitted with volt meter on dashboard) went dead a few days ago. I charged it, gave it a load test and it appeared fine. The car started and the voltage read a little over 14. I then noticed that after about 5 or 6 miles, the battery voltage dropped to a little over 12. I charged the battery again, overnight to be safe, and next morning everything appeared OK (14+/- V) untill about 6 miles out. - Voltage dropped to 12+/-.
I installed a reco alternator, obtained 14+/- volts initially but after about 5 miles it dropped to 12+/-. I immediately turned around and went back to the supplier and turned it off in their parking lot (still 12+/-).
I Came back out several minutes later, started up the engine and the voltage meter read 14+/-. Driving home from there, I kept a close watch and sure enough, at about 6 miles, the voltage began to drop gradually till it got back to 12+/-. Please note, a very gradual drop and nothing like an immediate failure.
Got home, parked in the garage and tested voltage with an external meter - 12.9. Turned engine off and waited several minutes, started up and low and behold 14.4+/-.
I have been testing voltage at both the battery terminal and also the terminal on the alternator - no difference detected.
Above, I have talked about miles but I believe that this is just a measure of approx. time and has nothing at all to do with the failure.
I considered the possibility of it being heat related but then the voltage recovery in the supplier parking lot does not make sense when residual heat build up under the hood is taken into account.
Is there some component e.g. capacitor, in the regulator circuit that could be slowly charging or discharging to cause this?
My next alternator is two days away from the same supplier and I am hoping that it was just bad luck with a faulty replacement but I would hate there to be an additional problem elsewhere which is dragging the aternator(s) down.
Any comments would be greatly appreciated
Terry, Fresno CA

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  • tjhm Nov 23, 2008

    Another alternator did the same so I had to guess that the problem was elsewhere. I changed the battery to one that I knew was old, gave it a bit of a charge, put a jumper pack on and started up. Alternator (voltage) appeared fine for one day then went beserk - however giving different symptoms. I concluded that the problem must be in the battery and went out and bought a new one. Charging voltage was fine for two days and then suddenly dropped. But listen up for this!

    I have just visited a Chevy site where some guy by the name of "redvette01" states that 2005 and up 1500 Chev trucks are fitted with a module that controls the alternator and, to conserve fuel, actually shuts it off when the battery is fully charged. NOW IT ALL MAKES SENSE!

    Redvette01, many thanks and also many thanks to NAPA who willingly took back the so called faulty alternators and gave a full refund. If anybody out there can help spread this, many hours of head scratching are going to be saved. HAPPY THANKSGIVING!

    Terry, Fresno

  • Anonymous Nov 30, 2008

    battery display show's not charging battery, alternator checked ok repalced battery after 30 miles battery display exhbits the same thing and the vechicle will completly die.


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This vehicle has a "Regulated Voltage Control" system. The computer reduces the charge voltage based on several parameters to improve gas mileage. Normally it shouldn't be a problem, but the computer will increase the voltage if you switch on the headlights. Also, if you're in Tow/Haul mode the voltage will increase.

Posted on Dec 01, 2009

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If the voltage drops happend only with this alternator only, I would be very inclined to say the problem lies in the compents of the alternator. I have to agree with you that I think its just bad luck with a faulty reco alternator. I went through a similiar thing with a brake sensor that was bad from the supplier (go figure). I would put money on you got a bad part from your supplier. Sadly enough this happends more than it should.



Posted on Nov 15, 2008

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SOURCE: 1996 Suburban. Does the brake pedal gradually go

You might have to bleed off the brake lines as there might be air in the lines if your pedal is too soft. check you level of fluid as well, your also better off bleeding completely and putting all new fluid in. process is very simple, all you need to do is bleed one side at a time by having someone pump the brake pedal until you have the fluid start to exit the bleeder. Then the same procedure for the other side, once you are done. Pump brakes multiple times before taking on the road. Try putting more and more pressure on the brake on your drive, the brakes will be soft for a bit then you should be in the clear. Good luck with your Chevy.
PS: try not to get any brake fluid on your rotors as it will not be good for grip when you want to stop that big truck.

Posted on Sep 22, 2010

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