I noticed a weird issue happening the last couple of days. When I start my 1996 Cherokee Sport, the alternator won't charge for up to 60 seconds after it start regardless of the RPM's. After this time it charges fine and does so until it shuts off. This only seems to happen when the vehicle has been sitting for a few hours as I can't get it to recreate the issue when it is warm. We had a major cold front move in during this time so that may have triggered something. The charging delays are also random, sometimes 5, 15 seconds and the longest was 60 seconds.

Tomorrow I'm going to check connections and voltage at the battery but wanted to run it across others to see if I should check the PCM/voltage regulator or something else.

 

I've seen this off and on on my 89 for last few years, most often in cold damp weather and winter stormy weather.
Your year volt control is in the ECM, my year it's in the alternator. so that is not common and I would say not the issue.
When you see this are you in a damp condition? perhaps mornings, some dew?
I see the situation most often when a very damp condition, or winter with a howling wind filling the engine bay (and my seat, bad door seal fit) with snow.
When starting in these conditions, there will be some belt slippage till the belt and pullies dry off, also some damp can be inside the alternator workings.
The good thing is you see the volts recover.
To find more info on the root cause you may need to experiment with a voltmeter at the battery, set it up just before you start and look at your readings quickly. Are you seeing volts on the meter, but not on your dash? So could it be the dash meter is slow to react? I've checked and had 31 1/2 volts at the battery terminals and at the same time having a low dash gauge indication. My suspicions are both on the in dash gauge and at cold starts, dampness on the belt. Through the summer, the symptom goes away.

 

Hey peep. 31.5 volts?
My battery shows 11.8v at rest, & 14.8 at idle

 

Tried it with a volt meter today at the battery. Constant 12v or maybe 11.9v with the engine running and issue ongoing. I ran it for a few min and the issue didn't go away. The dash gauge was showing between 11.5 and 12v the whole time.

EDIT: Took it for a 10-15min drive, it isn't charging at all now and the gauge is going down the more the battery is used so does this sound like an alternator or the voltage regulator module?

 

Sorry, 13.5V, (not 31.5)
Your rig is starting so the battery would seem reliable.
I'd have the alterntor as 1st suspicion prior to regulator.
Check Alt connections for good contact and tight.
Disconnect the battery positive lead from battery post, with the voltmeter you should see 12+Volts available on the wire from the alternator. If not, the alt is not functioning.
Some parts shops can do an Alt test under load, youl have to take it in.

 

Update, I replaced the alternator and it seemed to be the issue. I took it to the local Autozone and had them test it. It tested good and I insisted I wanted to buy new one since it was out and took a bit of effort to get this far. After debating with the sales counter person on "replacing a part that tested just fine" I went home, installed it and got the expected charge rates.

Funny thing is this is the second item I had AZ test that passed and ended up being bad afterall. Buyer beware with free testing.

 

That's great news and a good cautionary on the testing results. Glad to hear your up and running. For starters and alts here I go to Fergus Starter and Alternator, smack in the middle of the Fergus industrial park in the thriving metropolis of Fergus. Even for small town we do have the amenities, lol. They run alts thru a test machine that applies varied rpm and can put an electrical load on. The rebuild is only slightly less than new but I know the bearings are top notch and they stand behind the product warranty. So something to consider if you have a local rebuilder handy for that sort of compoent.
Here today had the 02WJ in for taillights, the battery was on it's last bark and failed right in the garage. With the snow and wind wailing away outside, can't figure where my luck came from, must be my birthday or something, oh ya it is! Tested the tail off the bat and even after a recharge. Fails on tester under load. Anyway picked up an new battery and a fresh terminal connectors to boot. Starts strong. As a note, prior to the replacement with the weak battery in, I recharged and did get two restarts. At the starts the engine caught (love the 4.0) and rpm was very low (only couple hundred) and engine was weak for about 1st 10 seconds, then the alt power came into play and the engine rpm and volt gauge came up to normal levels. So on the initial start prior to the alternator spinning up, the battery just barely powered the engine function. Just something to keep in mind for future. Checking the WJ maintenance record, l last tested that battery in June and the underload result was moderate, about 75% of rated. So it was inevitable.
Let us know if anything untoward reoccurs on your rig, else, happy trails!