What controls the air ride compressor on 1994 el dorado to turn on?

yes
if there is one side down then it is not a compressor problem but a ride height control valve
if the compressor was faulty it would be down all round

IAT is: Intake air Temperature sensor.
MAP is: Manifold Absolute Pressure sensor. This one seems more important than the air temp.

They come together as one device.
Try www.Autozone.com for more advise.

Hope this helps.

The problem may be in the controls on the dash, had the same problem in a 2000 El Dorado.

Check the engine bay. I saw a Park Avenue, about same year, with the compressor mounted, if I recall, on the passenger side, but definitely was in the engine bay.
If not there, most likely place would be in the rear wheel well area. Follow the air hose from the struts to the compressor.

Will run with defrost or blend selected on the heat control,to help dry the air,shoudn't run when floor heat is selected.

had same thing happen on my 92 el dorado. problem is at the blower control power relay the 2 plug connectors or the connector for the blower fan. theree is a flow chart to test the voltages going to these connector in the factory shop manual, for a 92 el dorado on page 1C-17 if I remember correctly. if voltages check ok then make sure plugs are securely plugged in. if still does not work, then it's the blower control power relay. good luck!

have the shift lock interlock solenoid checked out

use only a socket or if you have space use a ring spanner.NEVER use open ended spanners on any nut/bolt.except to stop it turning.....

this waring means that the ride control has been unable to maintain the correct ride height, this is caused in almoast all cases by leaking suspension air springs, the last on average about 100,000 miles

your shocks maybe leaking, have a tire shop take a look.