If that FS18 drags the 4.6 down when cycling you are pushing your luck. Grab the clutch plate on the compressor & turn it by hand. If it is gritty or notchy you have some parts to replace. Running it with 60f vents at idle means it is really low on charge. Driving it like that keeps it from retu...

Brielly: Go to https://www.eautorepair.net/Marketing/Default.asp And spend the 20 bucks for a one month subscription. You will get access to the FSM data and full wiring diagrams. The sensor calibration points. The fan logic path. And any temperature / pressure reference data that Jeep provided for ...

Your mechanical fan clutch is shot. The mechanical fan is the most powerful air mover under the hood. The electric fan is an add-on to help in extreme conditions and with the A/C. Again, Jeep has changed the aux electric fan operating parameters several times over the years. Some are supposed to com...

Does this vehicle have a mechanical fan and an electric fan, or only an electric fan?

Jeep has changed the fan configuration too many times to count.

What is the ambient temperature for those pressures?

Was this at idle or 1800 rpm?

Which engine in this truck?

System is either full of air, or your condenser is not doing the job.

How way it evacuated?

Any other repairs? Why was it recharged?

What is the ambient temperature?

Are those pressures at idle or 1800 rpm?

You are undercharged.

Charge 100% of the R12 charge.

The poor vacuum does not help. Not so much moisture, but remaining non-condensable gasses will raise head pressure.

If a 100% charge still leaves the evaporator warm in one place, you may have a defective evaporator.

90 psi on the low side port sounds like a stuck (or badly misadjusted) POA valve.

Here is a video of testing the POA:

https://www.youtube.com/watch?time_continue=68&v=PhWW7hD9-Yw&feature=emb_logo

Do it right, do it once.

Or do it over & over.

When the compressor fails, the shards will block a few passages in the condenser. Then the performance with the new compressor will be poor...