Green01XJ

I spent a good amount of time searching the forums but i didn't find anything that really matched my issue and answered my question. Whatever this issue is it isn't making the truck undriveable but it seems funky.

1999 XJ Cherokee Classic 4.0L

When i start the truck up and turn on the headlights and the defroster i can watch the voltage meter and every 5-10 secs the voltage drops from the normal 14 to around 11-11.5 volts. all of the lights dim including the headlights and the truck loses a good chunk of power. It stays down for maybe 3-5 secs and then jumps back up to 14 volts. this occurs while idling and while driving.

I have a video that i am attaching hopefully it works. Thanks in advance for any input



PS. Pay no mind my POS gas gauge as it drops an 8th tank in the 30 sec video. Goes whacky for about 3 starts when im around a half tank

DFlintstone

Besides checking your belt, you might want to check/clean the engine to firewall ground there, braided from the back of the head. If it's not your alt failing its probably wiring/connections/grounds so might as well check'um. Take a look while your at it for anything shorting, signs of burnt or chaffed wires. I'm thinking it's the belt.

Green01XJ

Wanted to bring back this thread with maybe a little update. I have removed and cleaned the firewall ground and the neg cable ground and put hen back in with some dielectric grease. I haven't done anything to be belt because it is not slipping or anything. A couple things to add to this though, in the summer when I turned my ac on what sounded like a constant belt squeal would come on. Soon as I shut the ac off it would stop with zero noise. After listening around for the source of the squeal (hurt my ears lol), I came to the assumption that it was the fan clutch in the ac compressor causing the squeal, not the belt itself. My repair was to be a man and roll the windows down. But now I'm wondering could this be related to my issue.

Also another thing to note was that sunday morning I went out to start my jeep ( ~28 degrees, slush on ground from day before jeep been sitting since the night before) and she wouldn't turn over. Went like this
Key on, all good all electric works, try to crank, everything dies no crank, key on, all good, try to crank, everything dies no crank. Key on, all good, try to crank, cranks right up a (lil weaker than normal but I've heard engines struggle way more). I've come across the electric works won't crank issue plenty of times with other cars boats etc, (enough power for electric but not enough to crank), but what baffles me is how it started the 3rd time. Again, possible relation? Jeep has not done this again yet and I DD it so I've had quite few starts since.

The voltage drop problem is the same. I've narrowed down its ways.

Any heater setting, no problem
Defroster no headlights, little drop
Defroster and headlights, big drop
Defroster headlights and off road lights, significant power loss

Sorry for so much detail you guys must hate me haha but more info is better than less. It's just an really irritating problem that I'd like to track down. Any input u guys have lay it on me it's appreciated, Thanx again

Green01xj

86-Chief

Hey Green. I have a few suggestions to help your jeep.

1. Get a higher output alternator and a better battery. offroad lights (ex. KC HiLites) pull a massive amount of power. the stock electrical system was never built to match the huge power draws of the aftermarket lighting systems on the market today. (a battery with a higher Cold Crank Amp rating could help the bad start in the cold)

2. Your ac clutch is frozen?
OPTION 1: replace the clutch.
OPTION 2: go to an auto parts store and by a belt for a jeep not equipped with ac and just pretend it doesn't have that system until your ready to fix it.
if the AC pump has failed, it can cause the belt to slow or pull, causing the alternator to slow charge rates.

3. The bad start in cold sounds like your starter is going bad. i had a 92 cherokee that did almost the same thing, but it froze up at the store. and it went on doing this randomly for a few days, then just quit on me and never turned again. it really has nothing to do with the temp outside.

4. your voltage drop problem.
it could be related to how much power your pulling from the vehicle system. if you upgrade your electrical system it might help.

beefmobile

did it actually try to crank when you turned the key? did it click like a dead battery?

if it just did absolutely nothing.....might be a neutral safety switch issue, which wouldn't really have anything to do with your weird alternator output. It happens to me all the time, the no start thing.

I don't really think this sounds like a bad starter unless you can actually hear something moving down there like the starter spinning or grinding. On the other hand, i went wheeling (in the YJ) one time and got out of the woods and stopped at a gas station, tried to start it back up and nothing. I had all my electrical components were up such as lights, wipers, radio, etc, but when i turned the key, nothing happened. Turned out that the wire going to my started has come undone at the fitting, but i doubt this is your problem since it started on the third try. My guess is still the NSS.

Green01XJ

Nss crossed my if it happens again that will be one of the first things I check. The motor did not try to crank at all just that "click" . And not that clickclickclickclickclick that u get with a dead battery, just a big "click", dead silence. I don't see anything being wrong with the starter because I just put a brand new one in last June when that died. I just really wanted to know if that was a relation to this voltage thing I'll deal with that another time if not. Thanks for the input

Btw, how many main grounds are there on the motor? I got the firewall- engine and the neg terminal is that all of them?

86-Chief

not sure how many grounds are on the 4 L i have the 2.5 and i can find 3 major grounds. your power draw might be a short to ground from something like a turn signal relay or something being that it is intervals.

rrich

You have the classic signs of a slipping belt.

Tighten it. If it's old replace it.

DO NOT USE ANY "STUFF" ON IT - IT WILL JUST MAKE IT SLIP MORE!

DFlintstone

***********Key on, all good all electric works, try to crank, everything dies**********

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Text-Book bad battery connection. Shiny lead, all 4 surfaces is what you want. Not saying your belt or alternator is cool, but right now those connections should be cleaned.

Mine idles over 14V with the high-beams and blower on high. 13 something is OK. You might try cranking the wheel doing that, work the PS pump. If that lowers the voltage much the belt is slipping.

86-Chief

thats what i said at first but he said its not squealing or squeaking?

86-Chief

its just weird that it loses voltage in certain intervals. i agree with the terminal connection too check the terminals and make sure everything is tight. but here is a way to test your alternator!

1)start truck with no accessories on
2)disconnect positive battery cable

one of two things will happen within a few seconds

a) truck will run like normal = good alternator output
b) truck shuts off / sputters / idle slows = take the alternator to auto zone for a test

Green01XJ

Hey Green. I have a few suggestions to help your jeep.

1. Get a higher output alternator and a better battery. offroad lights (ex. KC HiLites) pull a massive amount of power. the stock electrical system was never built to match the huge power draws of the aftermarket lighting systems on the market today. (a battery with a higher Cold Crank Amp rating could help the bad start in the cold)
This thing occurs even with the kcs off, even when there disconnected from the battery

if the AC pump has failed, it can cause the belt to slow or pull, causing the alternator to slow charge rates.

Is the ac pump affecting the belt even when the ac is off? How bout when the defrosters on?

3. The bad start in cold sounds like your starter is going bad. i had a 92 cherokee that did almost the same thing, but it froze up at the store. and it went on doing this randomly for a few days, then just quit on me and never turned again. it really has nothing to do with the temp outside.
Starter was just replaced in June, I know what thats like when one dies with the sllow painful cranks (finally died on me at 5am at the boat ramp for a bass tournament waiting to launch my boat )

Sorry about ignoring ur post in my last one, my phone didnt show your message only beefmobile when i responded

Green01XJ

***********Key on, all good all electric works, try to crank, everything dies**********

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Text-Book bad battery connection. Shiny lead, all 4 surfaces is what you want. Not saying your belt or alternator is cool, but right now those connections should be cleaned.

my contacts are so shiny they hurt my eyes lol, I also cannot tight i cannot turn them on the terminal like so many cars ive seen. Ive always been a fanatic about lil stupid stuff like that, gives me something to do when im bored

Green01XJ

This was my thought ^. i only get a squeal when the ac is on and personally it sounds like its coming form the actual pump

Green01XJ

I did this test, started the jeep, let it idle, pulled the + cable, ran like a champ, even got in and revved her up a lil bit, no problem, voltage still reading 14V. So i guess my alternator is good?

Thanks again guys for all the responses