2008 GMC sierra electricity problem. any experts?

[skog]

I have a 08 GMC sierra w/ 4.8L. Orginal battery. Truck starts fine even in cold weather but radio clock resets every morning. Voltage at battery when runing is 14.65, off after running 12.65 and after sitting all night with temps in the teens before starting 11.60. Any idea? Not a huge problem but annoying.

thanks

 

[lazy21]

Re: 2008 GMC sierra electricity problem. any experts?

Sounds like a battery problem! You should be 11.5-12.5 off and 14-14.5 while truck is on(does it reset if you turn your truck off?). Have you put a test load and your battery? You could also check your wiring, you should have a hot wire @ all time(memory) and another that goes hot when the key is on. Could also be a simple blown fuse on the memory wire.

 

[maccrazy2]

Re: 2008 GMC sierra electricity problem. any experts?

Look for a blown fuse for the radio. Most have 2. One for power and one for memory

 

[E. Bryant]

Re: 2008 GMC sierra electricity problem. any experts?

I think your battery is dying. 11.60V resting voltage is way too low. I'd recommend getting it tested at a parts store that offers such a service (many of this will do it for free).

If it's not a battery problem, then you likely have a parasitic load that is draining the battery. If it's doing it overnight, it's pretty major and shouldn't be terribly difficult to find.

 

[Cmonroe]

Re: 2008 GMC sierra electricity problem. any experts?

Battery issue for sure.

 

[CanSniper]

Re: 2008 GMC sierra electricity problem. any experts?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Cmonroe</div><div class="ubbcode-body">Battery issue for sure. </div></div>
^^+1
Also when you replace the battery, check the cable connections are clean. GM side post batteries are natorious for the positive post corroding. Dont just look at it and put it back together. Actually take the red boot all the way off and clean it using a good battery cleaning chemical and garden hose.

And another note, on some aftermarket batteries the hole for the post is drilled to shallow. So the bolt bottoms out before the cable tightens all the way down. You may need to put a washer on the bolt. This usually does not show up as problem for a couple of weeks later.

 

[lazy21]

Re: 2008 GMC sierra electricity problem. any experts?

2008 would be a top post

 

[CanSniper]

Re: 2008 GMC sierra electricity problem. any experts?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: lazy21</div><div class="ubbcode-body">2008 would be a top post </div></div>
HaHa your right! Disregaurd previous post.

You would think I knew better, was a GM tech for 10 years.

 

[skog]

Re: 2008 GMC sierra electricity problem. any experts?

last night when I left work truck started right up but radio reset. I set the radio ahead an hour and shut the truck off. Openned the door which kills the radio and interior lights. started truck back up and radio reset. drove home, about 7 miles. repeated test and clock stayed set. Battery is most likely the culprit as was suggested above. I just found it hard to believe that the clock cant stay set but the starter can turn the truck over without a problem.

 

[E. Bryant]

Re: 2008 GMC sierra electricity problem. any experts?

You'd be surprised how low the voltage can dip during a cold start if the battery is degraded. Most manufacturers require powertrain electronics to function down to 6V so that they operate properly during crank, and I worked with one German manufacturer who held that powertrain modules must function down to 4V because they'd seen the voltage dip that low during extreme conditions.

 

[songdogslayer]

Re: 2008 GMC sierra electricity problem. any experts?

I had a battery do the same thing. Would crank but than the radio memory and time would be lost

 

[ToddM]

Re: 2008 GMC sierra electricity problem. any experts?

Yep I've seen a battery do that on it's way to dying, it's that dip when the starter kicks in that does it.

Could be worse my dad got a 2007 new when he retired and it has a phantom electrical problem. Every once and awhile he will start it starts fine for a few seconds, and it dies right away. No codes, and if he restarts it it stays running and runs fine, happens every couple months. GM has tried various things, starter, alternator, tracing grounds, battery, airbag, seatbelt, etc. etc. and essentially given up on it. I'm sure it's some odd electrical thing somewhere but evidently these days trucks are too complicated for even the techs to figure out what's wrong if it doesn't give them a code to look up.

 

[gtofan]

Re: 2008 GMC sierra electricity problem. any experts?

When you get in the truck in the morning and turn the key to "ON" but without starting the engine, is the clock keeping time or is it reset at that point?

Is this the clock in the radio? I assume this is the only one but not sure. Mimmicking CanSnipers post, definately pull the boot and ensure the connections are clean.

How notorious are the ignition switches on these trucks for going bad? I know on the Trailblazer/Envoy the ign switch controls ALOT of functions and can wreak havoc when they go bad, I believe GM incorporates alot of functions to these switches in the full-size platforms as well.

I would clean the terminals and the ground contacts on the chassis then use a trickle charger overnight before you replace the battery. Then when you start it see if the clock resets and if it does perhaps this will help narrow down the culprit.

Any way you can switch a known good battery for a night?