Electrical Problem

[Spideerr]

Hello guys, new to this forum and I have a question to ask. I have an 03 Sierra 2500HD and I've noticed a "electrical surge" if that is what you would call it. While I am driving and I would get on the gas my trucks lights would dim and then would go back to normal. Same thing would happen when I would tow my race car with it going up hills and normal driving. That was the first problem. Now recently about a week ago my airbag light on the dash would say "service airbag" and the battery light would come on and then both would shut off and the lights would all still dim. Its really weird. Now I have done some research and I've heard about ground issues? Is there anything else I should check? Fuses, Broken Wires, Modules? Thank you for anyone who might be able to lead me in the right direction.

[diyer2]

Battery or alternator?

 

[Spideerr]

I’ll test them both later and see what the readings are? Test both batteries or just the main one? I know it sounds stupid but not sure what the secondary battery is used for in our trucks

[davester]

Assuming you've got a duramax, as they are the ones that come with dual batteries from GM, the two batteries are needed to start the engine.  They are connected in parallel, and are both connected to the vehicles electrical system all the time.

 

To test them, you need to disconnect both batteries and test them individually, and it is recommended that you replace both batteries at the same time if one is bad.

 

For my truck, the only time anything like that happens is when I use the power windows with the engine off.  But with the engine on, no dimming.

[Spideerr]

I actually do not have a duramax. I got a 6.0 in mine. Maybe was just an option that my truck came with, with both batteries. I'll test them both though