1985 Cherokee drains the battery overnight??

[tnman]

My 85 Jeep will drain the battery overnight. I had the battery tested (it's only 5 months old) and they said it tested good under a load. I can fully charge the battery but it will discharge overnight when hooked up to the Jeep. It just started doing this, one day it runs fine the next the battery was dead. I've charged the battery 2 or 3 times and checked to make sure there were not any switches or lights left on in the Jeep. When I charge the battery the Jeep will start and run fine, the alt light goes off immediatley when the Jeep is started. Any ideas what my problem is or how I can track it down? Thanks

 

[XJNick]

Hi,

The best way to track it down would be to use an ammeter (most decent multimeters have a 10-20A DC ammeter function), and see what circuits are pulling the power. This can be done by disconnecting the main circuits at the power distribution point (on early cherokees it is the starter relay's bolt terminal). That is where you can put an ammeter between the battery and each main circuit one-by-one to find which it's comming from. Or you can pull fuses one-by-one and see if it is a single circuit which is at fault.

-Nick :!:

 

[tnman]

Hi,

The best way to track it down would be to use an ammeter (most decent multimeters have a 10-20A DC ammeter function), and see what circuits are pulling the power. This can be done by disconnecting the main circuits at the power distribution point (on early cherokees it is the starter relay's bolt terminal). That is where you can put an ammeter between the battery and each main circuit one-by-one to find which it's comming from. Or you can pull fuses one-by-one and see if it is a single circuit which is at fault.

-Nick :!:

How much current draw is acceptable? I know there is a relay or something on the fire wall that charges up when the battery cable is applied to the battery, so there is always a little draw there.

 

[XJNick]

Hi,

To my knowledge most 30/40 Amp automotive relay coils pull less than 150mA (the brand of relay I commonly use pulls 138mA when cold). So if you have one relay who's coil is always energized, plus the clock and radio, I be looking for less than a 200mA draw -- if you get above that i'd start looking for problems and if you're above 1A current draw with nothing on, then I'd be pretty concerned.

-Nick :!: