Ok I can not figure out why my XJ keeps draining the battery while it is turned off. While it's on and driving it's perfect. when I turn it off 1 hour later it's dead. 2 brand new batteries, alternator barely been used maybe 100 miles driven on the alternator.
Any suggestions....

 

I'd have the alternator checked, you might have got a defective one.

 

Check your grounds and connections from the alternator and battery, the alternator mount is tight and the drove belt is tight. Check the alternator wiring harness. Clean the battery cable ends.

 

+1

I had to go through 3 alternators in a week because they were defective. (after the third, I demanded my $$ back and bought one elsewhere)

 

advanced auto checked the alt and it was good.
While I drive and right when I turn my xj off the battery is fully charged.
If I turn my xj back on within 30-40 mins after turning it off it's fine but much longer then that and it dies.
I can turn it on and unplug my neg and it still runs and drives no prob.

 

You have an 89... do you still have the cabling that originally came with it? My understanding is that in the earlier years there were XJ's that needed their alternator cable upgraded because the guage was too small. However... this problem only recently surfaced.

Maybe the cable is all corroded internally/melted the wiring from the inside and it's causing more resistance. It's a possibility since running a smaller guage, even only one size smaller, can make a cable run extremely hot depending on the amperage... and that's assuming the wire is in room temperature conditions. Put it under the hood with more heat and it increases.

 

Didn't think of that one. It is the original wiring. The motor is out of a 94 H.O. I swapped about 3 years ago but the wire harness is original...
Thanks for the input I will have to look at that and check the voltage coming from it see it if drains.

 

got a system? Check the light in the glove box. also check (if you have one) your hood lamp.

 

The test goes like this. Take a multi meter and set it to amps. Switch the red wire to the top plug (usually 10 amp fused). Take you negative terminal off the battery. Tape the black probe to the negative bat post and the red to the ground cable. That was hooked up to the bat. With the doors closed and the.underhood light off the meter should read between .2 and .4 amps. If its higher out have draw. To figure out what it is start by pulling relays under the hood. If it doesn't drop open the door and tape the switch so the lights aren't on. Start pulling fuses and looking for a drop. When the meter drops you have found the accessory drawing the power.

 

I have everything for the system but haven't put it on lol

 

Sweet thanks. My brother in law is heading over so this should be quick

 

Oh and another think sometimes an alternator will charge but still be bad. They can ground out inside and cause a 2 or 3 amp draw, sometimes more. If you can't find the draw take the positive cable off the alternator. If the draw goes away pull the alternator and check for continuity between the main bat+ lug (the big one the battery cable is hooked to) and the case. Resistance should be infinite. If there is continuity (resistance indicating a connection) the alternator is no good.

 

trying pulling the hot wire got the system just in case, had mine ground out on the body and it did the same thing

 

??

 

Trying that now.