1999 GMC Yukon problems

[Kevon67]

When I accelerate hard my Yukon drops in voltage, lights dim. If I accelerate gradually doesnt do it and I get to desired speed. Thanks in advance for your help.

 

[SunlitComet]

have a local parts store load test your battery and charging system. they can quickly find the issues for you but it sounds as if the internal regulator or commutator/brush is failing and your battery may be suffering as a result.

 

[Kevon67]

Thanks. I have 2 batteries running paralell. The battery that is connected to alt and all things vehicle is bad. The secondary battery is running everything

 

[SunlitComet]

When you get the battery parti
load tested disconnect the ground of each battery to load test each individually.

 

[gpracer1]

Mine did the same thing, anything over 3K rpms and voltage would drop. New alt fixed it.

 

[SunlitComet]

will need to study this more. something in the pcm about the 99 do this but not in 96-97 so far. I was able to start and run full throttle with accessories and lights on driving about 75 miles one day while waiting for a new alt. all off the bat.

 

[Kevon67]

I have a 220amp stinger alt. and two stinger 1500 batteries running paralell. All were installed back in April of 2007. I still have the alt that was about 2 months old prior to alt upgrade still in the garage. I will probably swap out and have stinger alt reworked.
I have aways run Optima Yellow Top Batteries. I f batteries need replacing thats what I will go with. Nothing against Stinger, I can buy two yellow tops for the price of one Stinger.

 

[Kevon67]

Thanks for the input guys.

 

[Kevon67]

Removed bad battery, which was primary battery, replaced with secondary battery. Problem solved. Thanks everyone for your input.