1990 yj electrical troubles
 

HELP ! My symptoms: Brake application drops fan blower speed, causes gas gauge to behave like an amp meter and go to "full". Fan switch on has the same effect, pins the gas gauge. Turn signal indicators on panel come on and off steady after brake application. Do I have a bad ground or a short? Can anyone tell me where to start looking, I'm down $300.00 so far, still not fixed.

Re: 1990 yj electrical troubles
 

A bad cell in a battery can cause this as well. Sounds like you are running on alternator power most of the time, and the dead cell in the battery is causing issues. Unsure if this is the cause, but I have seen this happen in the past... grab a used battery from the wreckers, and see if that helps.