gjdls95

I have a 1998 Jeep Cherokee Sport which keeps draining the battery and I can't figure out the root cause.


I measured the parasitic load and, assuming my meter is working, I'm seeing 15mV. I also pulled all of the relays and fuses from under hood and passenger kick panel and did not see anything. I just bought the Jeep 2 months ago and stored it until it got warmer to do some work. I fully charged the battery and connected it up and had 12.7V. After 5 days, the battery was dead and read only 5.65V! I pulled that battery and to make sure it wasn't the battery, I put a different new deep cycle battery from my trailer in and connected the cables to see if that battery would draw down. After 2 days the battery dropped 2V. Once the battery is disconnected from the Jeep, the voltage starts to go back up (although not back to 12+V).


Any thoughts? Are there any common failures which lead to this? I did pressure wash the engine quite a bit about 3 weeks ago before replacing valve cover gasket, rear main, oil pan gasket, distributor gasket, and oil filter adapter O-rings. Since I didn't have the car long, I'm not sure if this is the result of the pressure washing or if this was an issue previously.

Turbo X_J

Are you sure the draw isn't 1.5 amps? Do you get any A/C V out of the alternator when the engine is running?

kjc

I think you might be barking up the wrong tree.. check the alternator. Any battery will run down to nothing if it's doing what the alt. should be doing.

gjdls95

I'm pretty sure its 15 mA, if I move the range from uA-ma-A it's 15 mA. I could perhaps try another meter to confirm the meter isn't crap.

Regarding the alternator, the car is not driven as it's a surprise birthday gift for my daughter in a few months (I do start it periodically although I pull the battery and keep on a maintainer). The battery drains without ever running, just hookup the cables and it drains.


For the heck of it I measured the resistance between the battery cables (not sure if it makes a difference) and I see 75 ohms between the two, not sure if there is a "spec" for this.

Flowpro

When the fuses and relays are pulled out the battery will still drain? Or did you pull the fuses, look at them and then reinstall them? Just trying to clarify your quote above.

shadowman

I too am leaning tword the alternator being at fault, especially if you blasted it really well with the pressure washer. However, an old diagnostic trick to find an drain is to disconnect the negative cable on the battery, connect a 12V test lamp between the negative post and the negative cable. Since there is a drain (voltage signal returning to the battery) the light will glow. Next start removing fuses from the fuse block, the ones like radio and ecm will cause the lamp to dim(constant drain). Once you hit the offending circuit the lamp should go out or dim appreciably, thats where you start the search for your drain. If no change, try disconnecting the alternator wiring. If that gets it, guess what?
Just my .02

CCKen

A normal draw is between 5 mA and 25 mA (0.005 to 0.025 Amps). This draw is required to enable memory functions for the PCM, Radio, clock, and other modules.

You can pull the IOD fuse and see if the draw you are chasing is in the IOD circuit.

The FSM does state that an internally shorted Alternator can cause excessive draw.

gjdls95

I pulled each fuse and relay, one at a time, and the meter never changed, stayed at 15 mA.

gjdls95

I put the battery back in on Tuesday and measured around 12.5V and shut the hood, never starting or anything. Went out last night and the battery measured 9.25V so I disconnected the negative cable. Went out this evening to measure and the battery went back up to 11.75V while disconnected since last night.

gjdls95

If the alternator fails will it load the battery with the engine not running to draw the battery down?

Jeepin'Hubb's

My bros Ranger was just pulling 2.9A with everything off, tried all fuses and relays. Turned out to be a bad alternator.

Pull the alternator and take it to an auto parts store, they can tell you the condition of it.

Whiplash

^

if CCKen says it is so, then it is so

Turbo X_J

Yes, diode failure, that's why I mentioned checking for A/C V. As well if the vehicle has an under hood light does it go out when you close the hood?

gjdls95

The light fixture under the hood has been removed, only wire there taped off.


I just disconnected the wiring to the alternator and as soon as I connected the negative cable to the battery (positive was already connected) the voltage began dropping like a rock from 11.75V to 10.5V and continuing to fall within a minute. Now as I posted earlier, the battery voltage was as low as 9.25V yesterday, then I disconnected the negative cable, and the voltage overnight went back up to 11.75V.

gjdls95

This evening I made a homemade test light and hooked it up and it worked great. When I open a door the bulb is nice and bright so I know it's working well. With all doors shut and everything off, the element glows red but by no means bright. When I pull the IOD fuse the element goes out what appears to be completely. I think my meter isn't working as I measure the same 15mA current draw with the IOD fuse pulled. I also noticed that a relay clicks each time I connect the cables to the battery, sounds like it's coming from the passenger compartment fuse box. Since the test light doesn't come on at all with IOD pulled I would assume part of the power drain is related to the IOD (I know it provides "sleep" power). Any thoughts? I left the cables connected over night with IOD pulled, I expect the battery not to be drained tomorrow afternoon.