Air conditioning module A/C does not come on. Bypassed pressure switch, but compressor would still not engage. No voltage at connector on compressor. Refrigerant level was low, but now at specification. Still no power at connector. Checked all fuses and relays. Can it be control module and if so, how do I trouble shoot? Thanks

Check the switch for continuity. It should be signaling the pcm to turn on the compressor. Also check the low pressure switch connector. You might try bypassing the low pressure switch with a paper clip in the connector. If that works, you could just leave it bypassed or replace it. Check the continuity of all three wires to the pcm. They can be seen in the upper half of the diagram below on pins 38, 42, and 64 of the pcm connector.

Pump a jumper in the connector the low pressure compressor cycling switch near the accumulator canister to see if the Compressor engages. See picture of switch below, it is in the low pressure line or the accumulator.

unplug the low pressure switch in the air conditioner line near the dryer with air switched on , jump the connector with a short piece of wire to see if the compressor clutch engages. If it does your pressure switch is bad. If the pressure switch is good then there is a fuse near the compressor somewhere that may be blown. If it blows new fuse your clutch is bad.

You have to insert a can of R134A refrigerant and hose on the low pressure port.
Normally it is the fatter of the two hoses coming from the compre3ssor.It should then kick in with the A/C switch engaged.
If not you may have a bad fuse,switch,compressor,or relay.

The low pressure switch is just a sense input to the PCM - powertrain control module > Grantit , it is needed for the PCM to know the pressure in the system . But the PCM must energize the compressor clutch relay for the compressor to engage . Finding the compressor clutch relay in the under hood fuse / relay box an testing there would be the best place to start . Pull the relay out of the fuse box , look on the bottom ! You should see four set's of number's ,30 & 87 plus 85 & 86 . 30 & 86 should have B+ voltage . Use a multi-meter to test . 85 goes to pin # 1 connector 3 at the PCM . The PCM supply's a ground here to energize the relay if condition's are right . You could jump pin's 30 & 87 an if the compressor clutch coil is good ,the compressor clutch will engage . Video's on youtube showing how to do these test .

There are 2 pressure switches on the refrigerant lines. Pull off a connector and short the wires on the connector. If the clutch engages then the pressure switch is bad.

if the pressure of freon is to low the pressure switch on the receiver will keep it from running(the alum can near the firewall

The pulley on the compressor is always running when your engine is running, but the only time
it compresses the freon is when the clutch engages, if the compressor's pulley was not turning,
it would have already snapped a fan belt or your serpentine belt. voltage runs from your fuse box
thru your air condition switch on your dashboard to a low pressure switch that is located at the
accumulator a long cylinder,close to the firewall under the hood or close to the condensor, front
of the car. the switch detects freon pressure in the accumulator, if there is freon pressure, the switch
will stay closed and allow voltage to go to the compressor clutch to engage it and compress the freon,
if there is no freon pressure the switch will open, and there will be no voltage to air compressor, its a
saftey switch to keep your compressor from getting damaged.its possible that the switch could be bad
it may not have voltage at the switch, or it may be open because there is insufficient freon pressure.
check and make sure there is freon in the system.check for voltage at the low pressure switch if you have freon in your system and voltage at the pressure switch, set your ac on high, pull the molex off
the switch, and jump it out with a jumper wire, if the clutch engages and your car starts to cool, just
replace the switch. if the clutch engages but does not cool, then your ac system has some blockage
in the lines. if the clutch does not engage at all then it would be the compressor clutch. good luck!

This could be a few things. The freon could be low, one of the switches (high or low pressure) could be bad, or you could have a bad compressor clutch. You can test the clutch by checking for battery voltage and ground at the two pin connector with the A/C on if you have both power and ground, then the clutch is bad. You really should start by hooking up pressure gauges to the A/C ports to check the pressures, and these vary depending on ambient temperature and whether the A/C compressor is engaged or not. I am willing to bet that the freon is low though and may be just as simple as recharging the system.
Hope this helps. Good luck!

If the compressor kick's in when you jumper the relay socket there is no problem with the electrical to the compressor an the compressor isn't locked up . You have a control side problem , the PCM - engine computer is suppose to energize the relay if no other problems are present . The proper way to check this would be to hook up a scan tool an check pressure input's to the PCM an is the PCM getting a request from the HVAC control panel to turn on the A/C compressor . AutoZone is wrong as usual , There can be codes without the check engine light being on . o'reilly's is wrong as well DTC P0530 (LU3, LR4, LM7, LQ4 and L18)
The powertrain control module (PCM) or engine control module (ECM) monitors the high side refrigerant pressure via a A/C refrigerant pressure sensor. When the pressure is high the signal voltage is high. When the pressure is low the signal voltage is low. When pressure is too high the PCM will not allow the A/C compressor clutch to engage.

Action Taken When the DTC Sets
The malfunction indicator lamp (MIL) will not illuminate.
Diagnostic Aids
The air conditioning (A/C) compressor clutch will not engage under the following conditions:
• The A/C high side line pressure is over 2957 kPa (429 psi).
• The A/C low side line pressure is under 138-172 kPa (20-25 psi).
• Throttle angle is at 100 percent.
• Engine speed is more than 5500 RPM.
• Engine coolant temperature (ECT) is more than 121°C (250°F).
• Ambient air temperature is less than 5°C (40°F).
• Engine is idling at a low unstable RPM
Compressor clutch engagement cannot be used to determine status of the low pressure switch. The low pressure switch is one of several inputs to the HVAC control module for A/C request authorization. A/C request is one of several inputs to the powertrain control module (PCM) that control A/C compressor clutch engagement.
To accurately determine what pressure the A/C low pressure switch opens and closes at use Kent Moore GE-47742 which will allow the technician to measure the switch point pressure at the switch.
Using a scan tool, monitor the "low pressure switch" status while monitoring the "low side" pressure at the switch to determine the switch points of the low pressure switch.
The low pressure switch "connector seal" must be removed before plugging it into the switch for testing. The "plunger effect" of plugging the connector with seal into the switch induces a pressure on the back side of the switch, this pressure will skew the opening/closing characteristics of the switch 5-10 psi until the pressure bleeds off. The time required for the connection induced pressure to bleed off can take 20 minutes or longer

Do you have the proper diagnostic tools ? Factory scan tool , A/C gauges ? You best bet , take your vehicle to a qualified repair shop !!