ford a/c help needed?

Time out! Before you start dumping freon in, or pulling any out, let's make sure something obvious isn't being over looked. You mentioned you have 70PSI of static pressure on the low side, which I assume you also had 70 on the high side since the compressor will not engage. If this is correct, then you should have sufficient pressure to close and engage the low pressure switch if it is functioning properly.

Since this is a 1996 this tells me the car is equipped with OBD 2 diagnostics, and more than likely the ac compressor is controlled through the PCM. Before you go and start jumping things you need to check a couple things first.

Start the car and let it run a few minutes with the a/c switch on. Unplug the clutch cycling switch (low pressure switch) and check to see if you have 12 volts to the Tan and light green wire. If you don't, then your problem is long before the clutch cycling switch. You didn't mention if you had electronic climate control. If you do, then that is a whole other problem itself.

But let's assume you do have the 12 volts to the clutch cycling switch. Do not jump it at this point. Plug it back in and then go to your high pressure cut out switch which is a 4 wire connector. Check for 12 volts at the red and yellow wire. If you have 12 volts there, plug that switch back in and check for a signal from the pink and light blue wire. Yes this means you are going to have to pierce the wire to check it, because the swtich needs to be plugged in to check it with the engine running and the a/c on. If you have a 12 volt signal coming from there, your final check is the Constant Control Relay Module.

The CCRM is on the passenger side of the vehicle near the radiator support. It has a 24 pin connector on it. Access is kind of tight, but you are looking for a 12 volt signal coming into it on the pink and light blue wire. Yes you will have to pierce the wire to check it with the engine running. If you have the power there then your final check is the black and yellow wire coming out of the CCRM. Is power coming out. If not then you have a failed CCRM.

Back to the beginning. You noticed I said at the beginning if you didn't have 12 volts coming to the low pressure switch to begin with, and you have electronic climate control, you may have a failed sensor inside the car. I can't begin to explain the diagnostic steps there.

But the checks I gave you for the outside of the car can be completed in about a half hour.

Vacuum the system (rent a pump) and bring the system down to -20 and let set for 20 min and see if its still at -20 if not find the leak, also the pump will remove all the air and moisture in the system, charge the system with oil first, at -20 of mercury on the guages it will pull the charge into the system, then put about 3 cans of 134a in, no need to start the car until the vacuum in the system won't pull any more in, then get a small piece of wire and unplug the the plug on the dryer (canister on firewall) and make a jumper with your wire from one side of the plug to the other, turn your A/C on to MAX and fan to high and start your car and add freon until it comes out cold, do not overfill, but make sure its COLD, and stop the car remove jumper, and plug it back in, and your good to go.

Take the low pressure sensor wire and unplug it.Now with the ac turned on in the car, go back to that plug and jump it. The ac compresssor should come on now When it's jumped,Try to add the freon.If that works after the first can plug the plug back into the sensor.