94 Jeep Grand Cherokee runs hot when the air Conditioner is on good otherwise what would cause this?
The ZJ including '94 did not come with an electric fan. I would
look into your fan clutch being bad, this is attached to the
cooling fan via the water pump.
First, would be to check whether or not the electric fan is
coming on. Set the emergency brake for safety, make sure the Jeep
is in park, hood open, motor running, turn on the AC and see if the
electric fan (located against the inside of the radiator) is
running. If not, that would be your root problem, and answer why it
seems to only happen when the AC is on. If you have a bit of
testing background, unplug the fan itself (the plug is located on
the left side of the shroud), and see if there is 12v from the feed
(not the fan) side. If there is, there's something worng wirth the
fan itself, if not, it's more than likely the relay.