Accepted Answer

XXXXXX,

There is a possibility that the system is only very low or out of refrigerant. Once the system gets so low the compressor will stop working all together. I would have the refigerent checked for a low condition first then go from there. If it turns out that the compressor is indeed bad you can replace it but to finish the job correctly and prevent any cooling problems it is best to have the system put on a vacuum with a machine first. It should be pulled down the 30in of vacuum and left there to see if it holds for at least 30mins. This will help find out if there is any other leaks and remove any moisture that may enter the system from having it opened while the compressor is being changed. Here is a description of system shutdown reasoning and the procedure for replacing the compressor. The system should be evacuated by qualified personal to keep refrigerent from entering the open air. Refigerent under pressure can cause personal injury so take care when servicing.

This system will also set codes to help diagnose exactly where the problem lies down to low refigerent. It will not turn on the check engine light but will store codes. It may be best to have the computer scanned for AC codes first.

 

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A/C COMPRESSOR CLUTCH CONTROLS -1999 Buick LeSabre Cu Page 1 of 1

 

: BONNEVILLE, EIGHTY EIGHT, LESABRE, PARK AVENUE & RIVIERA

Description

When A/C mode is selected, a 12-volt signal is supplied to the A/C
request input terminal of PCM. A/C clutch relay is controlled
through PCM which also monitors A/C refrigerant pressure. If A/C
refrigerant pressure and engine operating conditions are within a
specific calibrated acceptable range, PCM will enable A/C clutch
relay. This is done by providing a ground path for A/C clutch relay
coil through PCM. When A/C clutch relay is enabled, battery voltage
is supplied to compressor clutch coil.

The PCM will enable compressor clutch whenever engine is running and
A/C has been requested, unless:

lThrottle angle is greater than 90 percent.
2
lA/C head pressure, is greater than 414 psi (29.1 kg/cm ) with
A/C refrigerant pressure sensor reading greater than 4.27 volts.
2
lA/C head pressure is less than 34 psi (2.5 kg/cm ) with A/C
refrigerant pressure sensor less than 0.35 volts.
lIgnition voltage is less than 10 volts.
lEngine speed is greater than 4225 RPM for longer than 5 seconds.
lEngine speed is greater than 5280 RPM for any amount of time.
lEngine coolant temperature is greater than 257°F (125°C).
lIntake air temperature is less than 32°F (0°C).

Diagnosis

1.If On-Board Diagnostic (OBD) System Check has not been
performed, see appropriate SELF-DIAGNOSTICS article in ENGINE
PERFORMANCE. If OBD System Check has been performed, go to next
step.
2.Check for any DTCs that may be set. If any DTCs are set, perform
diagnosis for that DTC first. See appropriate SELF-DIAGNOSTICS
article in ENGINE PERFORMANCE. If no DTCs are set, go to
appropriate MANUAL A/C-HEATER SYSTEMS or AUTOMATIC A/C-HEATER
SYSTEMS article for diagnosis and repair.

 

A/C-HEATER SYSTEM - MANUAL -1999 Buick LeSabre Custom Page 1 of 1

 

COMPRESSOR

Removal & Installation

1.Discharge A/C system, using approved refrigerant
recovery/recycling equipment. Remove compressor drive belt.
Raise and support vehicle. From underneath vehicle, remove A/C
compressor splash shield. Disconnect transmission oil cooler
line bracket.
2.Unplug electrical connectors from compressor. Remove bolt
retaining refrigerant lines to compressor. Remove remaining
compressor mounting bolts and compressor.
3.To install, reverse removal procedure. If more than one ounce of
oil was drained from compressor, add same amount of clean
refrigerant oil to new compressor. If less than one ounce was
drained, add two ounces of clean refrigerant oil to new
compressor.
4.Tighten compressor mounting bolt to 74 ft. lbs. (100 N.m).
Tighten compressor mounting nuts 37 ft. lbs. (50 N.m). Tighten
refrigerant line retaining bolt to 22 ft. lbs. (30 N.m).
Evacuate, charge, and leak test A/C system.

 

 

 

 

 

 

 

Shawn

 

Edited by LSx Tech Shawn on 7/12/2008 at 6:34 PM

Expert:	Shawn
Pos. Feedback:	100.0 %
Accepts:
Answered:	7/12/2008

ASE Certified Technician

PA Certified Inspection emissions, ASE Brakes Suspension, Lead diagnostic Tech.20 years exp