My daughter has a 1997 Cherokee Sport 4.0 that is doing some weird stuff. Battery was dead and she had to have it towed, driver told her it was an alternator because it died while she was driving. I pulled the alternator off and had it checked and it was good, so I put it back on and got a new battery. Ran fine for a few days when it happened again. She was pulling it off the interstate and it suddenly it started sputtering, she kept giving it gas until she got it to a parking lot. She said it was running fine and then suddenly the heater blower stopped working and it began misfiring. Once it in the parking lot it would not restart.
I trailered it home and when I jumped it it was idling really high, so I changed the air control module and the spark plugs. It started up and ran fine for a while until I went to turn on the heater and suddenly it started sputtering and died. Weird. Had to charge the battery, started it again and once again it ran fine, heater blower worked and could drive it down the road without any problems. What's the deal?
Seems like it is a wiring issue or maybe a bad blower relay? Not sure why that would cause the whole vehicle to suddenly start running horribly and then die over a bad relay. Posting this to see if anyone has any ideas or have had similar issues. Very perplexed.

 

It sounds like the blower motor is pulling electricity from where it needs to be going during running is why it behaves poorly. Electrical stuff is strange like that to our understanding. The blower motor circuit uses a lot of power and can easily be the cause of this type of thing. It sounds like this problem will totally kill the new battery very soon if it is allowed to continue.. In the meantime disconnect the battery or pull the HVAC fuse whenever it gets parked to protect the new battery.

With the battery being dead after it sits obviously a parasitic drain is occuring. With the symptoms it sounds like it may be with the HVAC system. You should test for a parasitic drain and look for voltage drop. There are a couple of different ways you can test for being able to see.

If you pull the fuse you can place paper clips in the terminals, and then clip the multimeter leads to those paperclips checking for milivolts abnormally on the system when it should have none with the Jeep powered off. You can use a conversion table to convert this reading into current and see how much AMPS the system is actually draining. The idea is just to find and verify where the drain is happening. Then, you are able to confidently hunt through for the source of the parasitic drain. It serves to verify when re-checking things as you go along, and to see if you have the problem fixed at the end. Whenever you unplug certain components.. you go back to the fuse and check to see what is now happening there with it.

The fuse has a connector with wires bundled together on it associated to it. The fuse allows power to go to and from that bundle of wires on the connector. This connector with these wires should be grouped together with a few others like it near to and basically on the fuse panel. With the multimeter showing the drain you unplug those connectors one by one. Doing this can show you which one of them the fuse is associated to when the power drain at the fuse gets eliminated after you disconnect it. After you find out you can start pulling each wire off the connector and reconnecting the plug again to see which exact wire has the fault and is responsible for causing the drain. In this way you will know exactly where to go for finding the fault. You can trace that wire frontwards and backwards to find the location where the fault is specifically happening.

It might be the blower motor switch itself or the resistor is the reason. You can use the fuse panel to find and see what happens. Or, use the multimeter on the battery in different ways to see. Disconnect the resistor and see if the drain stops. Disconnect the blower motor and see if the drain stops.

If you place the multimeter on the battery terminals to see the voltage. It sounds like over the course of several hours I bet you may actually be able to see the drain as it is happening. Run the engine and then let the battery settle over 45 minutes. It should read between 12.5 - 12.7 VOLTS after it settles. With a drain the voltage will continue dropping to 12.2... 12.0... 11.8.... etc. With a big drain like yours on a new battery you will be able to watch it happen going down consistantly point after point all of the way down to dead battery status. Over thirty to forty-five minutes of watching it should be obvious for you to see it. Once you have the suspect component disconnected you will see the battery voltage halt and begin to rise..

You could also inline the multimeter to the battery with the battery cable disconnected to see the AMPS drain happening as a different approach.

After you narrow it down you can try replacing components or tracing the wires to them if that fails to fix it.

I wonder does the blower motor continue to run super slow and barely audible when you have the power turned off to the Jeep?

(edited):
I think I misread. The battery is only dead after running and not when sitting overnight? It acts up when driving with the blower motor on though... It is kind of the same thing in a way. It probably could mean there is voltage drop within the HVAC system either way. The same type of tests as above can be used. With it running you will probably be able to see the voltage draining at the battery all the same. Testing at the fuse to see what type of current is on it there while it is running (with the fuse remaining plugged in.. testing its external contact points). You may have to test each wire individually of the bundled connector to the HVAC fuse with the Jeep on while running the HVAC to see what each of those is doing in order to know exactly where to look though... You could jumper each pin to its terminal and see what happens with the battery voltage.

Or, the alternator as said below. I would definitely re-test the alternator since it is the charging component.

 

Do some alternator testing yourself with a volt meter. I personally have had 2 or 3 altinators tested at parts stores and came back good but where shot. Chances are all you need is a new altinator and all will be good. Your heater draws a lot of power and being your battery keeps going dead id put my money on that. You should also do a parasitic drain test on your battery just to make dure before you purchase any parts

 

Most problems with my 98 have turned out to be pretty basic, loose or bad battery cable, bad ground etc. im currently testing for stalling on my jeep that i thnk is due to weak battery(dont drive it very much). Jeep(Chrysler) products are famous for not idling or running rough if low battery or poor terminal connection to battery. Good Luck!

 

Had the alternator tested at a auto store twice and I have a tester on my battery charger and everything says it is good. I am going to try and change the blower resister and then go from there. The weird thing is it will be running perfectly fine and then suddenly start misfiring and acting like it is going to die. I guess she was running the heater with the blower on and had been driving for a good 20 minutes or more and then it just started doing that before it died completely and wouldn't start. Sounds like a short but, who knows. It obviously happened when I turned on the blower once, and everything went to crap. But it sat for a while and I restarted it and everything was fine again and the blower worked. Weird stuff. Hope to work on it this week but the temperature just dropped to 10 degrees and I really don't feel like freezing my butt off to work on it. Lots of good ideas to check, thanks to everyone that responded.

 

Put a blower resister on today, the old one was really corroded and rusty but still not sure if this was the issue. I started it up, everything worked fine, took it down the road and saw that the voltage gauge was not moving. Got it back home and put my battery charger with the alternator tester and it said the alternator was no good. I turned the Jeep off and it was dead, I had started it at least 4 times before this happened but every time it turned over really slow like wasn't going to start but did. Now it is dead. Going to check the connections to the alternator, may possibly buy a new one but really tired of chasing the possibilities. I had the alternator checked twice at the store and they said it was good both times... very annoying.

 

I know its cold out but have you tried removing all heating related relays and fuses, charging it back up and running it for a couple of days to see if problem goes away?

 

Go to bleepinjeep.com and watch their video on finding a parasitic draw. Most multimeters people buy won't measure amps high enough for checking circuits in a vehicle, but you can measure the voltage at the test ports on the top of the fuses and if you get any reading, it shows there is amperage being drawn in that circuit. It's called the voltage drop method and there are charts online you can calculate with, but any reading at all shows there's a draw.

Hint: if the rear wheelwells are rusted, pull off the cargo area side panels and check the electrical connectors back there. My trailer lighting module shorted out from water getting in and corroding the connectors.

 

What voltage do you see between the two battery posts with the engine running?
Running fine after the battery has been charged and no reading on the dash voltmeter (if I under that correctly) indicates to me that there is a problem with a connection somewhere. Seems that the battery is not charging via the alternator. Cables to battery often corrode internally and develop high resistance. I would consider changing the cables and clean up the related ground connections. Even if there are other problems the battery cables likely are not in the best condition and you will eliminate related issues.

 

This is great advice right here! The video is a really good source of information. It helps to show how simple this actually really is to do too. I think it only sounds complicated or confusing.

Even though I do not agree with everything how it is shown being done in the video. It was just that I preferred a slightly different approach was all.

I had a huge drain on mine. It sounds like mine was somewhat similar to what is happening on yours. I did not really have a good idea on how exactly to find it to get it all figured out at the time. The same videos mentioned here are some of what I researched and watched prior to when I tackled the issue. This was very helpful to me watching this for a similar type of situation as your Jeep seems to be having...

 

For referencing as an example;

My drain was on the rear windshield wiper motor. This was causing my alternator to only just barely charge the battery. After finding the wiper motor drain and disconnecting it, my alternator went right back to charging normal at a full 14.XX VOLTS.

That was not the end of it for mine. Mine actually had two parasitic drains happening on it at the same time. The wiper motor was interfering with the alternator output charging ability. The other drain was not doing anything like that but, the second parasitic drain would totally kill my battery in less than 4 - 5 hours whenever the Jeep was turned off. This second one was located on the little floor courtesy lamp/bulb on the passenger side floor area. By looking at it I could not tell. It did not look like the lamp was remaining on any. It was though.. The cover to it is opaque and this did not let the tiny little bit of light out any at all to see it, which was remaining illuminated when the Jeep was fully shut down. I found the location of the drain by testing wire connector pins and terminals with a jumper (associated to the fuse that was showing a drain), and coordinated doing this with the abnormal current showing on the fuse circuit. After finding the wire having the drain on it. I had to look at the wiring diagram for this color wire, and it told me there were several things located in it. I disconnected those things one by one, until the drain being shown at the fuse suddenly stopped. This was how it got found to be the floor courtesy lamp circuit causing the problem.

If I can find it.. I will link the thread I started on it, as it shows how I found the drains being similar to how the BleepinJeep video shows you.

 

I do not know how to link it. This is the exact title to how I found the voltage drop which was occurring on my Jeep in case you wanted to look it up by using the search function.

Battery drains to 11.6V in 1/2 day 1997 ZJ

 

Just checked out bleepinjeep, Good site, Thanks for sharing