Hi, I own a 93 Cherokee 4.0 5 speed.
I don't know electrical issues outside of the ignition, though I did just order the headlight wiring harness upgrade
My voltmeter is always in the red on the right (Overcharge?) whenever the engine is running, but just to the left of the center hash mark of the gage when the key is in the on position and the engine off.
I don't know if this is related, I'm assuming it is, but if I'm driving with my headlights on and use the fog lights (stock ones) or cruise control, the headlights flash on and off. The other day, they started flashing on and off without me using them at all though.
Anybody have any ideas what it could be?

 

Have your alternator and battery tested.

The voltage regulator is built into the PCM, so there's no upgrade/replacement for it other than replacing the PCM.

 

Suggest you clean up your terminal connections first...battery posts, ALL the ground connections. Make sure everything is SHINY clean! Search this forum to find where they all are (I do not know for the '93)

 

Before doing ANYTHING, grab your DMM and verify the gage reading (the OEM IP volmeter is a notorious liar. The earlier it is, the more it lies...)

Then, while you've got your DMM out, find my writeup on testing primary electrical and go through it.

I used to have to repair those test benches they used at Autozone et al, and I can tell you one thing for sure - they're not worth a damn. They'll tell you alternator voltage output, but at less than 500mA draw. That's not even enough to run a good flashlight.

The important stat is current, while maintaining >13.0VDC.

If your alternator is overcharging, that could be either due to a wiring fault (the PCM senses low system voltage and ramps up regulator output to compensate. Grab wiring diagrams and check) or a failed/failing alternator (rather unlikely, since alternator voltage usually drops as it fails,) or, rather rarely, a failed/failing regulator circuit in the PCM (which requires replacement of the whole module. If I have to have a regular built into something, I'd rather have it built into the alternator - easier to replace, and cheaper. The saving grace of the ChryCo plan is that, apparently, their regulators very rarely want replacing.)

The ChryCo regulator, as I recall, uses PWM to control alternator output (Pulse Width Modulation,) which means that the only satisfactory way to check regulator output will be with an oscilloscope...

 

Yep, get the meter out. It's probably your gauge.

 

Would that explain the headlights flashing on and off when I use the fogs or cruise though? (I'm an electrical idiot, by the way)

 

Separate issue. The headlamp switch, speed control, dip/full beam switch, &c &c all run through the steering column loom, perhaps you've a pin or two in one of those "harmonica" plugs getting loose.

As far as the fog lamps? That switch is on the panel, not the column, right? Usually, it's the other way around - the fog lamps are wired to come on with the headlamps on dip beam, and cut off on full beam (which makes sense - if you run full beams in fog, you deserve to crash from white-out. Hell, I turn my headlamps OFF in fog, and drive on my 35W amber fog lamps. Can see better & farther that way...)