99 Sub, Headlights, domelights, guages are all pulsing dim to bright every second. Alternator output seems fine 14+volts. Also the power steering stopped working at the same time. I think my wife tried to jump start a lawn mower and reversed the polarities (although she will not admit it) any thoughts??????

 

possibly the drive belt(s).

 

Do a load test on the battery any parts store should be able to help you. Same thing was happening to my vehicle and then the battery died. It could definitely be the problem and it is an easy fix.

 

Check the ground on the motor and body. A bad ground will cause all sorts of odd behavior.

 

Any updates on this one? I have the same issue and I have replaced the battery already. My truck has been doing this for about a year and everything else is working fine.

 

I see this is an OLD thread, but just on the off chance anybody is looking... My 99 K3500 has been doing exactly what the origional poster described. I'm inclined to replace the alternator, although I see one poster found a battery to be the fix. Anybody got any further input?

Ralph

 

Welcome to the forum ,
I would be inclined to suspect poor grounding or the alternator....