Reversed jumper cables on 1999 jeep Cherokee sport. Battery seems to be ok, but no gauges and no start. Will crank, and electric fan comes on with key in on position.

Battery ? connections , Cables

you meant NO CRANK RIGHT? ill pretend yes.
2.5L stick shifted.
no, there is only a clutch pedal switch.

if you use a voltmeter this is easy.
but that is last. not first.
Head lights work , bright,
battery terms clean
does hotwiring the starter solenoid crank the crank shaft fast?
yes, then the starter works and key line is dead.
no, then the starter is bad, (assumes battery good and charged)

1st ,first is jumper cable starts. does that crank engine?
off a running donor car. AAA tow truck style.

with an ohm meter check if the wires going to the relay have power when they should. next use a jumper wire from the pos. battery terminal to the power connector on the fan if the fan starts to run off the jumper then its probably the relay to blame. hope this helps.

you need to have it connected to an OBD2 machine and watch if you are missing the cam sensor showing RPMs
or if your missing crank sensors RPMs,
it could be a wiring problem or computer if your seeing the RPMs from both sensors,and the last thing i would check is hooking up a fuel gauge to the reed valve and watch what fuel pressure you have while cranking,if the cam sensor is the culprit it will turn the fuel off after the cranking.

your battery is dead from cranking it so much. Charge the battery and then it should start

Alternators are known to go bad on jeep cherokees. I would try putting a new one in.

Seems to be a chronic problem with crank position sensors... On yours it is tested between b&c terminals and should have no continuity there. (should show an open circuit if good)

Replace the battery and check the charging system after replacing battery.

Try putting the car in neutral and starting. If its a manual trans it might be the clutch pedal safety switch or it may be something as simple as a loose battery connection.

I HAD the same problem with 95 Cherokee for over a month, Turned out all I needed to do was Clean Battery Terms and Replace the Ground Clamp on Batt Cable.

It is a ground problem.