A 1998 Jeep Grand Cherokee has gone through 3 batteries in the last 3 months. While they have all been replaced by warranties, it'd be nice to get the problem solved permanently. I've tested the alternator, and it's not defective. I'm suspecting it might be a short somewhere in the system. How can I track down if this is a short, and if so, where the short is occuring?
Standard digital multimeters can measure current and help you identify what in your vehicle is consuming your battery's juice. Get an electrical diagram of your vehicle and try to narrow it down by doing current measurements in the various major paths of flow. When your car is off, no (or only trace) current should be flowing. Every time the path of electricity splits, you'll have to test each to determine which one is drawing the juice. There's no telling how many of these you'll have to check before you reach the problem.
This answer of course assumes the juice is being drained while the vehicle is off. I suppose it is possible that it is draining while on also. Either the alternator is bad or it isn't able to produce enough juice to keep up with your vehicle's demand (which probably includes some defective component that is sucking lots of juice). If it keeps running normally, it might be worth checking the leads coming to the battery (while still disconnected) with a meter to ensure it is being fed properly by the alternator.
By the way, please do this before doing any more battery exchanges. You are making the price of my next battery go up by taking advantage of the return policy like this.
In addition to an unexpected electrical load, as covered by Captain Claptrap, there are other things to check.
The two biggest killers of lead/acid batteries are overcharging and vibration. Unless you have the equipment and the skills to use it properly (in which case you probably wouldn't be asking) I suggest you get the charging system checked by an independent auto electrician.
For the vibration issue, check the battery mounting. The battery should be sitting very solidly on a surface without any hint of rocking. Remove any mat this might sit under the battery before checking this. That surface in turn needs to be mounted very solidly, with absolutely no sign of movement relative to the rest of the car. A common problem with some cars is that the mount has supports which attach to the fender, which can flex a lot.
If all the above checks out ensure the battery hold-down does its job properly and does not allow the battery to move at all.
If you find any issues with the mounting, no matter how small, have that fixed under warranty, otherwise you're just going to keep replacing batteries.
Same problem, but another forum suggested that the key in their 98 GC can be removed one click past the OFF position, in the ACC on position.
Sure enough, I checked mine and found the battery drain was due to the key switch being left in ACC and then being removed. The key shouldn't come out there but it does. I screwed a small metal bracket to stop the key switch from going to ACC on. Problem solved.
Wow I can't believe the basics are totally not listed here.
First of all, since you know its draining the battery, disconnect the battery, charge it, then check to see if it is still draining on its own. Saying that for anyone that hasn't tried that first to double check the battery itself.
Then there are the basics. The alternator check: you can use a multi-meter to check the input from the alternator while the battery cables are attached to it.
Next, hoping that the starter relay is good if you have one, there could be the possibility the starter solenoid has crossover and is draining the battery. Even though you can take the starter to an auto parts store to check it and they ok, it's standard operation (ie: the motor works under load and they can engage the solenoid) they seem to never be able to check if the solenoid is draining, only that it shoots out the bendix fully.
Before you go buying a new starter, there is also the possibility the issue could be the key insert or an electronic position module on the steering column that the key insert moves manually. A quicker way to check that any internal cowl component is not an issue and NOT have to go through all the fuses, is to pull the main electrical plug to the cowl from the engine compartment that supplies its electricity.
That only leaves engine components as drain possibilities. If you still have the drain, it may be the starter solenoid. You can replace the entire starter as a unit or just the solenoid if it is a separate component. If it doesn't drain the battery, it could be the key insert or the module it controls, or some other issues as mentioned before.
If the starter does not solve it, and the key insert isn't the problem, as a last resort, the starter relay may be allowing pass through, but they usually are good for a long time.
I know this is an old forum, but I need to comment. I have a 1998 Jeep Grand Cherokee Laredo that I bought for my daughter to use. The battery was brand new when I got the Jeep, but soon after purchasing it I would find if it sat a few days without driving it the battery would be completely dead. I searched online, asked my mechanic friends and didn't hear of anything that made sense to me. Today, I had some time and an empty garage so I again tackled this annoying issue in hopes to get to the bottom of it and finally figured it out :2thumbsup:
I read a lot about the MUX/T TOW fuse that is under the hood as that is where my draw was coming from, about 175 mA. I read that someone had a bad door switch in the back door (hatch) so I tore in to the door and while having the DC amp-meter installed in the 50 amp fuse location, I started unplugging different connections under the plastic cover of the back hatch. After about a minute, I noticed the amp draw dropped to 12 mA, so I started plugging things back together and found the latch switch for the glass window was the culprit. I left the hatch switch unplugged to avoid that problem later. I will crack another beer and maybe I will attempt one of my other many tasks. :cheers2:
I can say the easy way for you is to get a low amp tester. Remove the negative cable of your battery, connect the tester to the negative side of the battery and to the negative cable of vehicle. The light will come on if there is a drain somewhere. If there is, remove fuses 1 at a time. Every time you remove a fuse, check the light. If it goes out then you know at least what circuit is draining your battery. Then you know what and where. You can take it from there.
I have the same problem. I put my amp meter in between the positive lead and the positive terminal of the battery. It should draw 1/4 amp at rest. If it doesn't leave the amp meter inline as is and start pulling fuses.
My case was two fold , the power amp to the radio which is located under the rear seat. That dropped it down 8 amps or so. Still too high. I then began to troubleshoot the rear door switch.
Also I found if I just locked the truck by the key the alarm system would still draw too much current. But by locking the system by the truck key switch, the problem fixed it self. yea . I figured this out after my wife decided to tell me this. I love to bang my head.
You can have your starter relay checked if you do not have a multi-meter. You should also check your voltage regulator. Both items have contact points inside their covers (like the old point systems) and with moisture getting inside can cause these points to rust together which in turn will draw juice from your battery while the engine is off. I have had this happen to me while owning a Chevy, Ford and Chrysler.