I have replaced the Battery Altenater and Voltage regulater and still battery looses all power when headlights are on.
Can run several days and fine but one 30 min drive with headlights on and battery goes dead. Can any one help me with this.
Thanks

 

Sounds like a temporary short to ground. It will first KILL your batteries, one cell at a time. Second, it also sounds like when your lights are on, that your alternator stops charging your battery. You either need a mutimeter on that circut (charging side) while you turn the lights on and off and try varying loads like a/c, radio, cigarette lighters, running lights, power seats, etc. or install a voltage meter to SEE what's happening while driving.

The quick and easy one is shown below.

 

Whats the application/MY?

 

I don't understand your question.

If you're asking about the gizmo in the picture, it's just a plug and play voltage meter that just about anyone can use.

 

Sorry oldschool1..

My post was in, or should have been a response toAtastevens for the vehicle application/model/year info...

 

hehehe
It's all good.
Just as long as we can get Dude's truck to stop eating electrical components