Volt meter showing discharge

[Guana]

Drove blazer the other night and noticed when putting on the running lights or brake lights the volt meter would peg out negative and eventually battery died.

Brought blazer home, charged battery back up and began to troubleshoot:
>started blazer disconnected neg post and truck died
>noticed post on rear of altinator were burnt
>had alt tested showed good but still replaced
>installed new alt if you rev up engine volt meter shows + if you put the lights on goes neg


Do any of you have any other ideas.......thanks

[FireBros.]

Did you get the battery checked?
A bad cell in the battery could act like that.

[cleszkie]

I am assuming that you are talking about the ameter that is reading negative or discharge, not the voltmeter. If alternator is OK, then you have a short somewhere that is bleeding off the charge produced by the alternator. The short could be in the battery (bad cell) or elsewhere. The short is obviously bleeding off more juice than the alterantor can produce so it is a significant. The ignition should continue to work off the alternator even if the batter is removed.

On another note, are you running an externally regulated alternator? If so, check/replace your voltage regulator. Many charging issues can be solved with a new voltage regulator.

[Chulisohombre]

Sounds like regulator bad. Bypass it with a single wire alt. I did it with a summit 100 amp alt and all is good now.

[Guana]

Thanks for all the help, it was a bad regulator. It's back up and running.

[FireBros.]

Sweet.