Battery drain

JRHODES61

MEMBER
1988 JEEP WANGLER YJ
5.7L
V8
4WD
AUTOMATIC
7,000 MILES

I’ve had some charging issues on my vehicle recently. Replaced alternator, battery, starter, starter relay. Checked grounds. Starts okay and I read 14.3v while running at the alternator and battery. Problem is battery drains within 2 days. I test with voltmeter across negative battery post and disconnected terminal and get a reading of same as battery typically 12.7v. This can’t be correct? I’ve pulled fuses individually no change. I’ve disconnected alternator no change. Disconnected starter no change.
Help

1 Reply

CARADIODOC

MECHANIC
33,916 POSTS

It can be expected to find voltage. You're connecting the meter correctly, but you need to be reading current, not voltage. There are a whole new set of procedures on newer vehicles starting with around the mid '90s, as those can draw up to three amps for 20 minutes after the ignition switch is turned off. Switching to a lower range for more accuracy after that 20 minutes will result in a blown fuse inside most digital meters. You don't have to worry about that on an '88 model.

Taking two days to drain the battery is typical of a half amp drain, and that is very close to what a common 194 "peanut" bulb draws. You'll often find one of those in the glove box. Be sure there's no bent bulb holder mounting bracket or something else preventing that light from turning off.

Here's the diagram for the power circuits. You'll see there's some things that come before the fuses you might be pulling out.

Image (Click to make bigger)