Hi.

I’ve got a battery drain on a stock ‘91 XJ I can’t find.


All ABB/ABS dealer disconnected it looks like. I’ve no airbag, electrical fan disconnected for the test, nothing else going on- stereo yanked out no off road lights or stereo wires shorted.


Here’s what I’ve done, Testing for drain on the (-) battery (-) to ground with ammeter:


-Pulled all the fuses out of the driver’s interior fuse box (one by one)- no change.
-Disconnected the battery and connected just the starter, small drain (.5~.6v max)
-Connected the PDC and full 12.6v drain.
-Disconnected the lead to the stater, down to 12.0v drain
-Pulled all the fuses in the PDC out (one by one), no change -full 12+v drain.
-Pulled all the fuses out everywhere, no change -full drain.
-Took apart the PDC, seems normal to me (?)


Whenever the PDC is connected I’ve got 12v~12+v drain.
-Went through and disconnected EVERYTHING I could get to and cleaned every connection in the engine compartment. No change! As long as the PDC is connected to the (+) battery post, fuses or not, I’ve got 12+v constant drain.




I’ve got a Chilton’s manual and it’s got about the most useless electrical schematic I’ve ever seen- to use that I’ve have to strip the entire wiring harness out of the truck to figure out what’s what and where it correlates to the diagram.



So what am I looking for? I’m guessing there’s supposed to be a constant hot going out of the power distribution console (?) but where does it go? I’d rather not clip the whole wiring harness apart if someone knows something here or has a better (useful) schematic.


I’ll try the ignition cell tomorrow but maybe someone has some ideas in the meantime about where to check next?




Thanks!

 

mostly you check current with an amp meter. my 00 reads .014 amp, 14 milliamps.
with a sensitive meter you will always read volts that tell you nothing.
gotta read milliamps.

i have no idea whats norm for yours

 

Disconnect alternator.

 

^Yep^
Seems you've disconnected everything except the alternator.
One typical failure with them are shorted or leaky diodes draining battery current to ground.

 

Do the interior lights work (like come on when the door is open)? Bulb connection could be shorted to metal. Does the Jeep run?

You can download a factory service manual with better wiring diagrams...

 

ok.

Jeep runs fine if I don't let the battery die down over a weekend. dome/courtesty lights just stopped working with this problem. the one in back is pretty rusted.
I found some decent schematics online too.

So,

Alternator tests fine- diode within specs (0/825), and charges 14.6-7 dropping down after a bit once it brings the battery back up (I haven’t checked for AC leaks yet). It’s not the diode shorting anyway.

I also checked the starter, no drain HOWEVER the solenoid pulls 1v rapidly dropping down (0.01/sec) initially once connected.




Went back to the beginning, testing at the PCB/Relay box by the battery.

new fuses in the interior box, charged battery, clock and fans disconnected, no radio in.
started with the big fuses, immediately with everything off,
putting fuses in front to back working from the battery-feed (after putting in the 60a ALT-PWR-1 which was fine), got a 30a ENG CTRL 12.6v drain. Everything downstream from that in the PCB also had a drain once this one is in.

Tested new fuses, putting everything back together, Connected battery, ECM pulls 12.6v, power antenna runs constant, blew dome, radio and ETR fuse and the power doors quit working. Otherwise jeep runs fine and charged the battery back up.

Once I shut it down, I disconnected power antenna and ECM still pulling 12.6v. Starter lead also pulls that slow initial 1v dropping down less and less (capacitor unloading) even with everyrthing disconnected. I get 12.6v ECM pull from the 30a PCB fuse in the relay box the moment I connect the PCB to the battery with eh ECM fuse in.


Bad ECM or is it trying to deal with power ant?

Anyone run power to the ECM via the IGN-ON lead? Can that be done on this year/model?

 

without a current reading you know nothing about drain. use an ammeter in series with a bett cable.

 

Look for the simple things first when you're battery is going dead. Rarely caused by anything electronic. I think it's something simpler than the ECM. I've never heard of an ECM shorting internally. I think if you're blowing the dome/radio/ETR fuse, that should be a cause for investigation. You can pull the dome lights and disconnect from harness to see. I'd disconnect the power antenna harness too. Another potential cause. Also, if power locks aren't working, that could be a shorted switch that is trying to unlock the door. The dome lights and the power locks are one of the few things powered when the Jeep isn't running. If you have a key-off drain issue, you should look at things that are powered when the key is off. Just my $0.02.

 

do you have any idea what the current drain is.

spec is .005-.025 amp

 

I am dealing with same issue. Parasitic drain when Pdc connected. ECM and all maxi fuses other than alternator disconnected remove drain