electrical problem

[debo4x4]

as i was backing out of my driveway yesterday.....i noticed my radio cut off then back on and the compass reset like i had turned off the truck. the lights also dimmed and the rpm's got really low like the truck was going to stall, but didn't. then everything seemed fine, but by the time i was pulling into my office the truck just died and would not re-start. i popped the hood and noticed my battery has acid leaking out of the positive terminal. so at lunch i put an optima red top in and she fired right back up. the idle was a little rough since the battery had been disconnected for a few hours, so i drove around assuming the computer just needed to re-learn. i also went by autozone and had them test the alternator, which they said was fine. so all went well until i was leaving for work today, and the same thing with the radio and lights happened again. and now when i come to a sudden or quick stop the rpm's drop again like she's going to stall but doesn't. also, when i am just sitting in park and roll up both windows, all the lights dimm very badly and the voltage meter drops to around 9v until i let go of the buttons. this really seems like the alternator to me....what do you guys think it could be? thanks in advance!

[99silveradoz71]

Sounds like an alternator to me. Slow turn signals and dim lights(unless you rev the engine). The radio fading out.

[sperry]

Even though it starts with a fresh battery, check the cables and connector hardware. That acid could have migrated into a cable for some time.

 

Not always an easy diagnosis using a message board!

 

If nothing is visible, measure some points with a voltmeter. Alternator lug, battery (-) terminal with the meter's (-) on the block or chassis. As well as other similar tests.

 

Look for voltage drops accross wiring that just shouldn't be there.

 

I use a clamp-on DC ammeter to check faults like that, but not exclusively.

 

You may just have an intermittent condition in the alternator that didn't show when it was checked.

[budhayes3]

Could be the alternator or high circuit resistance. Like sperry said, that acid may have worked it's way into the wiring, and you may have an internally corroded battery cable. If you do a voltage drop test on the battery cables (each one individually) and see more than half a volt, then there's high resistance in the cable and excessive voltage is being wasted there.

 

If my memory serves me right, one of our members recently had a similar problem that he traced back to a bad battery cable.