Disco dies with lights on

[gogodisco]

I have a 97 Disco. the alternator and battery check out okay, but the battery dies at night when the lights are on. Driving without lights is no problem. i can't figure it out. Please help!

 

[greg409]

I'm going to a s s u m e that when you tested your alt - it was a load test - about a minute or so. (not just voltage output)
Same with battery.

Having said that, how's your serpentine belt? just because it doesn't squeal and isn't cracking, does not mean it isn't slipping.

Throw a decent voltmeter on your batt, start your truck, turn on your lights (& other loads)
and watch your voltage for at least a minute.

I don't think it should go below 12.5 or so.

When you're looking @ your belt, the ridges underside should be fairly sharp, indicating good groove contact.

check ALL your electrical connections @ alt,batt,grounds,lights,etc.

luck,greg