99-05 Chevrolet/GMC/Cadillac All Full Size Trucks and Utilities A/C Low Pressure Switch Diagnostic Tool - kw manual automatic air condition A/C side pressure PSI inoperative poor performance warm hot

The following diagnosis might be helpful if the vehicle exhibits the symptom described in the PI.

Currently the A/C low pressure switch open/close pressures cannot be accurately determined by measuring pressure at the low side service port on 1999-2005 full size trucks and utilities. The evaporator is between the low side service port and the A/C low pressure switch. Correlating switch pressures measured at the low side service port are difficult to predict because of the multiple variables that impact pressure drop across the evaporator.

Special Tool # GE-47742 allows the technician to monitor the actual pressures at which the switch opens and closes within the suspect vehicle’s refrigerant system. The following steps should be followed to determine if the A/C low pressure switch is opening and closing within the proper ranges(Open 20-25 psig/ Closes 40-46 psig).

1. Disconnect wire harness connector from low pressure switch and remove switch from the accumulator/dryer.
2. Install low pressure switch to threaded port with O-ring on tool GE-47742.
3. Install GE-47742 with low pressure switch attached to the accumulator/dryer.

** IMPORTANT: Removing the seal from the wire harness connector is required. Failure to remove the seal before plugging it into the connector will lead to misdiagnosis. 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 psig until the pressure bleeds off. The time required for the connection induced pressure to bleed off can take 20 minutes or longer.

4. Remove seal from wire harness connector.
5. Connect wire harness connector (less seal) to switch.
6. Connect ACR2000 low side gauge to service port on GE-47742.
7. Use the Tech 2 to determine the low pressure switch status and the ACR2000 to determine low side pressure. Simultaneously monitor the switch status and pressure at which the low pressure switch opens and closes while operating the vehicle under the following conditions:

•	Engine (On)

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A/C (On)

•	Aux Blower (Low)

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1500 RPM

•	Frt Blower (Low)

•	Aux Temp (Full Cold)

•	Inside air/ Re-circ

•	Frt Temperature (Full Cold)

•	No Sun Load (In the Shade)

8. The Tech 2 displays switch status as "Normal" for Closed and "Low Pressure" for Open.
9. A properly operating switch should open between 20-25 psi (138-172 kpa) and close between 40-46 psi (275-317 kpa).

Notice: Remember to replace the connector seal when diagnosis is complete. Failure to replace seal could cause terminal corrosion.

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Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance.

(99-05 Chevrolet Silverado) and (00-05 Chevrolet Tahoe, Suburban, Avalanche) and (99-05 GMC Sierra) and (00-05 GMC Yukon/Denali, Yukon XL/Denali) and (02-05 Cadillac Escalade, EXT, ESV)

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