YJ battery drain / voltage leak

Anyone have suggestions why my '88 JY (4-cyl) drains the battery overnight? How to find it and fix it?

I have been unable to trace the source of the slow current leak, it's not anything obvious. Seemed random and intermittent at first but has been getting slowly worse over several months, and now is a daily PITA. Possibly may be worse in hot weather.

Battery will hold a charge okay if disconnected.

 

I would start at the fuse box. Unplug all non essential stuff. Likely a wire shorted somewhere. Ever replace the alternator? I had a connector go bad on one once. Dielectric connector gunk on fittings seemed to also help. Not sure but I had a few battery charge issues before someone mentioned that to check...

wife had an 88 escort gt when we met in 91 (that car went 140k before we sold it). High output escort. I guess. Cruise control never worked. Over time I found two things, like separate issues, may be related. A shorted wire from a rub above the dome light, and the stupid disconnect switch on the clutch or break or both... Another had rubbed wire and the position was always pressed iirc. A wrap or six of black tape on the rubs and reposition of switch to the pedal and we were getting 35 to 40 on the highway 'feet free'.

 

I don't think this seems like a short, since it is a slow draw-down. More like the 'ghost' consumption of the radio and clock, but enough to kill the battery in 24 to 48 hours.

Tried testing at the fuses, without any luck at identifying a problem circuit.

I did replace the alternator at the start of this issue because I thought it wasn't charging the battery fully. But I'm still wondering if it might be feeding back at night?


Very basic vehicle, no cruise control or clutch disconnect or anything like that.

 

Electrical demons suck. Just saying. I hate 'em.

Sorry, just some RAG/WAG steps I've gone thru in the past in that previous post. Here's a couple more:

I try and think of the 'always hot connections' first: oh, to be young again... digression over... back to the jeep...

Could it be the ignition switch? May be it's not fully clicking to the off and is remaining partially in 'accessory' mode? If you got it 'second hand' may be the po had a shot-put for his key fob because I know you're not hanging 2lbs of brass keys off your key chain - and wore out the switch? That usually has other indicators tho as well.

somewhat related: Could it be a starter solenoid not fully opening or closing (? don't know these things well other than when they don't work at all when they go for me?)

How about a light switch? It's always hot, may be the connection needs cleaning.

Can you un-plug the radio and other 'accessories' fully so there's no draw? Dang radio in my boat (hate it to start) has LEDs and does something with the CD player that eats the batteries if I don't kill the batteries at the marine cutoff switch.

do you have 'idiot lights' for doors or something similar that might be not fully opening?

What about salt and such where you are? Have you given the thing a full high-pressure squirt at the car wash or in the drive way? May be there's something that's corroded in some way that is 'hiding' and water will 'un-hide it'.

Start with connections and 'scrape/sand them' then reconnect and test. (ouch - potentially a time warp here).

We had a '78 Int'l Fire Engine when I worked for the USFS in '91. It had similar issues, so the mechanics just plumbed in a marine shutoff switch to the batteries. Nothing better than jumping in to go 'red' and getting the 'whirr-wrhirr-rrr-clik-click-ggnnnnng' then having to walk into the office from the bay to call dispatch and tell 'em to roust the volunteers as we were 'out of service for mechanical' and to get the effing mechanic here again. Even better if it'd roll out of the bay and we could pop the clutch in 2 to get it going.

good luck.

 

You normally use a test light to look for low amp battery drain. Is that what you are using?

 

I have been using a multimeter, but the battery always shows a a slight draw under normal conditions, for the clock and radio.

I've tried checking one fuse at a time, and looked for a voltage differential at each one but that has not seemed to lead me to the fault. Makes me suspect it is on an unfused circuit.

Or that maybe there is a gremlin in the clock or the radio? Not so simple to isolate, the wiring harness is not easy to trace in all it's wrapping, connectors, etc.

I do indeed have a battery disconnect (like our Dept fire trucks) and use it each night, but then I lose the pre-sets on the radio, and have to reset the clock everyday.

 

Maybe try pulling all the fuses except the one for the radio and letting it sit? At least you'll know if the radios the culprit or not. If it's not, you could always run a fused constant hot from before your battery disconnect to your radio to keep your pre-sets while still being able to disconnect everything else.

 

There should be fuses for the radio and clock. I would remove those also and check.
Are there any aftermarket items installed? I always check those first as I've found they are commonly the culprit whether wiring added for towing, external radios or lights, etc.

 

You will never find a low draw (drain) with a volt meter. (Trust me) As tumbleweed #6 states, otherwise your wasting your time.

 

The radio/CD was aftermarket, makes me suspect it. But not on a separate fuse.

I'll get to work with the test lamp.

 

Not spent time on it lately - other priorities.

I'm not sure what measuring across a fuse shows, except resistance in the fuse?

Would it make more sense to measure any voltage difference from each fuse to a direct battery positive, thus show any slight drop in a circuit that is 'active?'

 

The theory about measuring voltage drop across a fuse is that a draw on that fuse will heat up the fuse material causing higher resistance which will show on the volt meter. This means you have to know the fuse resistance without a load then with the connected load. Not only time consuming but if you have a dozen fuses you need to run a log on all the readings for comparison. If you use the test light and remove a fuse and still have the draw, then leave that fuse OUT and pull the next and so on. If after pulling all the fuses you still have the draw then you know the problem is some where in a direct wired circuit like the alternator, horn, starter solenoid, etc: etc.

 

Thanks Walt. My intuitive thought was that the draw is so small it wouldn't heat a fuse, but I'll try to see if there is a clue there.

 

Thanks, will do. Right just now the custody lawyers are getting all my time and money.

 

Disconnect your alternator, it's possible the diodes are going bad.

 

I think I've found the problem (...fingers crossed).

Finally started to see erratic intermittent undercharge/failure to charge (as seen at the dashboard voltmeter, and dimming lights.) Only happened when hot, and very unpredictably on-again and off-again.
I've replaced the alternator and as yet no dead batteries at night - although I did buy a new battery just previously.

So, as postulated above by myself and others, I suspect the slow battery drain was the alternator's internal regulator diodes leaking back while parked and shut down.

The irony is that the problem began back around the time I replaced the alternator once before. That was because the voltmeter had showed erratic over-charging - but it seems the OEM voltmeter itself was the true problem, since eventually cleaning the voltmeter's rear terminals 'cured' the apparent over-voltage spikes.

But by then I had replaced the alternator with the current one, thinking it's regulator was bad. It was confusing to have a dead battery repeatedly, at the same time as the other issue. Especially since it came and went randomly, my attempts at testing were no help. I didn't figure it out until now, many months later, when the bad regulating issues on the new unit became serious and obvious. Too late for my poor battery!

Confirms to me my theory that the newest part is often the one to suspect first.