AC problem The ac goes on and off randomly. I replaced the relay, the IOD fuse is ok. Many of the same vehicle does this. The ac low pressure is ok. What next Brian

In a 1994 Chevy K1500, the compressor should receive power when the AC button is turned on, assuming that the system is adequately pressurized and there are no other issues preventing it from engaging. Here are some steps to diagnose the issue:

1. Check Refrigerant Levels: Low refrigerant levels can prevent the AC compressor from engaging. If your system is low on refrigerant, it may need to be recharged. This is typically a job for a qualified technician.
2. Check for Refrigerant Leaks: If your system is low on refrigerant, it's essential to check for leaks. A leak can cause the refrigerant to escape and prevent the compressor from engaging. Look for signs of oil or refrigerant leaks around the AC components.
3. Fuse and Relay Inspection: Ensure that the AC system's fuse and relay are functioning correctly. You can consult your vehicle's owner's manual or a fuse box diagram to locate the relevant fuses and relays. Replace any blown fuses or faulty relays.
4. Check the Pressure Switch: Many vehicles have a high-pressure and low-pressure switch in the AC system. These switches monitor the pressure in the system and can prevent the compressor from engaging if the pressure is too high or too low. Check these switches for proper operation and continuity.
5. Inspect Wiring and Connectors: Examine the wiring and connectors leading to the AC compressor. Look for damaged wires, loose connections, or corrosion. Ensure that there is no damage to the wiring harness.
6. AC Clutch and Compressor: If all the electrical components are working correctly, you may need to inspect the AC clutch and compressor itself. The AC clutch should engage and disengage when the AC is turned on and off. If the clutch isn't engaging, it may be faulty, or there could be an issue with the compressor itself.
7. Refrigerant Pressure Sensors: Some vehicles are equipped with refrigerant pressure sensors that can prevent the compressor from engaging if the pressure is out of the specified range. Check if your vehicle has such sensors and test them if necessary.
8. Professional Diagnosis: If you've checked all of the above and cannot identify the issue, or if you're uncomfortable working on AC systems, it's recommended to consult a qualified automotive technician or AC specialist for a thorough diagnosis and repair.

Remember to prioritize safety when working on your vehicle's AC system, as it involves high-pressure refrigerant and electrical components. If you're not experienced in automotive AC repairs, it's best to seek professional assistance to avoid injury or damage to your vehicle.

Could be several problems. Depending on what vehicle you have you may have high and low pressure switches. If the freon is low, the low pressure will not let the compressor engage. The ac controller could be bad not sending current to the AC clutch. If you have power to the relay, depending on the vehicle, the relay may not be getting a ground signal.

Looks like the low pressure switch gets power from a 10amp ac fuse. Power then goes to the ac relay which is powered on by the ac heat controller on the dash. Power then goes thru the high pressure switch to the compressor. The ac relay is grounded to the body. Do you have power on the lite and dark green wires going into the relay and is it grounded ?

Check the a/c fuse in the under hood fuse block. If the fuse is good swap the a/c relay with one of the other relay that is the same part number in the fuse block. If the compressor still will not turn on than you will need a high end scan tool to look at the a/c data in the PCM.

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

A mechanic would start at the compressor and work back.
Did you jumper the low pressure switch, or the relay, or put power directly to the ac clutch ?
You have a low pressure switch that should be closed and a high pressure switch that should be closed to put power to the compressor clutch. If the freon pressure drops below 20psi the low switch opens, if it goes above 300 psi the high switch opens.

Some possible causes are the system is low on freon, a faulty compressor clutch, faulty low pressure switch, relay, fuse, or control switch.
Do you have power at the fuse and the relay ?

some of these newer ac systems use safety pressure switches on the low and the high pressure lines , ck and see if yours has 2 and ck accordingly,,,goodluck...

I'd bet money it's your Rear Evaporator, located behind the back right tire. Mine just went out, which cost $200 to discover, followed by $811 to replace. My co-worker has the same vehicle, and had the same exact problem six months prior. If you google search for "06 grand caravan evaporator" you'll find similar posts. And it's not a recalled item, as of this writing.

whenever the ac system has been opened it should be hooked up to a vacuum pump designed to evacuate the ac system of any foreign debris and oil etc and after should be able to hold a vacuum to show that there are in fact no leaks then if all is ok at this point you can then charge your ac with the proper freon specified for you car when the pressure reaches satisfactory level the ac compressor will then cycle on you should not bypass the low pressure switch

try removing the plug off the low pressure switch on the accumalator plug a paper clip into the plug and turn ac on if it comes on then your low pressure switch is bad or your low on refigerant.