Question about 1996 Chevrolet Tahoe
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.
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 !!
Posted on Apr 11, 2017
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Posted on Jan 02, 2017
Most likely a loss of refrigerant ( freon ) in the system. The A/C compressor uses a low pressure switch as a SAFETY to insure it wont turn on without freon in the system. Hope this helps.
Posted on May 18, 2009
SOURCE: a/c blows hot air at idle
u have a trinary type switch on the high side somewhere on the high side,,,it may have 2 or more wires going to it and it is mounted on the high side line/or compressor,this is ur problem
Posted on Jul 09, 2009
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