A/C compressor will not come on

I followed your instructions to clear the ACM codes but the compressor will still not come on. I am still getting the messages "low refrigerant A/C off" and "Service A/C system". What now?

There are two sensors on the high side (small tubing) and one big one on the low side (one inch + diameter tubing). Which one of the two would it be? One is near the dryer and one is on the drivers side. Can I replace it without loosing the Freon and/or can I jump it out to see if it is bad (I think I may have done that already?) If I understand you correctly, even after I find a problem and fix it I will have to reset all the error codes on the dash. Can I reset them all or just the ACM? I know this is a pain but I have been at this for weeks and as you can see at considerable expense.

The low side (large tube) sensor has a pink and a green wire. The high side sensors are black and grey on the passengers side of the tube and dark blue and black on the drivers side. Let me know which one and if I can jump it out before I replace it. Also can I replace it without loosing the Freon?
Thanks.

I bought the new high pressure sensor from Cadillac but we still have problem. There are two sensors on the high pressure line that runs along the firewall from right to left. Parts dept at Cadillac says there is only one according to their diagram. I don't want to replace the wrong one (assuming that this is indeed the problem) and loose the Freon multiple times. The high pressure line starts at the passengers (right) side of the firewall and travels across to the drivers (left) side of the car and then turns down below the master cylinder and then turns forward toward the condensor and attaches to it. That line looks like 1/2 inch diameter (guess) aluminum tubing. The line coming out of the evaporator (enclosed in the fan box assy) is 3/4 inch diameter (guessing) and gets reduced to 1/2 inch at the coupling that joins it to the high pressure line. There is a sensor on that 3/4 inch line (right before the coupling) that has a black and a grey wire attached to it and when I jump out the relay to engage the compressor that line gets ice cold. It changes to extremely hot right at the coupling point where it is ruduced to the 1/2 iinch line. That 1/2 line gets untouchably hot all the way across the firewall. The second sensor with the blue and black (looks black to me and not green) is located on that 1/2 in line all the way over on the drivers side of the firewall. Which one do I replace? Is the proceedure after replacement to clear the codes on the diagnostic (all of them or just the ACM?) And then recharge the system, or the other way around. Thanks for your patience
Bob Smith

I still have the problem. I have replaced the two temperature sensors and the two low pressure sensors. I have cleared the ACM codes through the onboard diagnostics that you showed me. The system is full and works fine when you jump out the relay in the fuse box under the hood. Both low pressure sensors read 12 volts (+ - ) and both temp. Sensors read varying 4-5 volts. I have even tried jumping out all four of them but the compressor will not engage. The ONLY way it comes on is when I jump out that relay (replaced it three times to be sure it was not the culprit). Do you have any more suggestions? Lastly if I take it to Cadillac will their diagnostics be able to read the problem and would a heat/AC shop have the same equipment or is Cadillac my only option? I am at my twits end now.
Thanks for you time,
Bob Smith

Wow! Thanks for the information on the A/C compressor. It worked and saved us lots of dough!

1997 El Dorado compressor not coming on due to low refrigerant.
So. I cleared all codes then started the car and turned on the A/C. The compressor immediately came on. While it was on I added more refrigerant to it. It took the refrigerant and started blowing very cold air.
So, clearing the codes tricks the computer into thinking the car is not low on refrigerant and the compressor immediately came on as soon as I touch the A/C button.
I hope this will help someone having the same problem.

Followed the reset procedure closely. I couldn't get my A/C running even though I had it filled, jumpered the hi and low psi sensors, etc. I am an HVAC tech and was out of ideas. I kept reading about resetting the PCM and/or ACM plus kept reading that Cadillac fault codes latch and will not allow whatever it monitors to just start working again. ACM fault codes must be reset. Figuring out how to do that s the trick. JACK42 had the right sequence. It worked after messing around for days. I already had the problem fixed and only needed to reset the ACM. Until it is fixed, you won't be able to reset it and stay that way for long. Thanks Jack42!