Cooling Insufficient - Air Conditioning (A/C) System. Buick Century 2000

For 1990-2009 cars only

Makes 🢒 Buick 🢒 2000 🢒 Century 🢒 Engine 🢒 Engine Controls - 3.1L (LG8) 🢒 Cooling Insufficient - Air Conditioning (A/C) System

Table 1:	Insufficient Cooling Diagnosis
Table 2:	A/C Performance Table

Test Description

The following test measures the A/C system operating efficiency by comparing:

•	The ambient air temperature at the time of the test

•	The ambient air humidity at the time of the test

•	The pressure at the high-pressure side of the refrigeration system

•	The pressure at the low-pressure side of the refrigeration system

•	The temperature of the air being discharged from the LH and RH center IP outlets into the passenger compartment

The number(s) below refer to the step number(s) on the diagnostic table.

This step determines if there is enough refrigerant in the A/C system to operate it without damage.

This step is to determine if the A/C compressor is operating.

This step measures the performance of the A/C system.

This step is to allow for vehicle variations as well as high ambient temperatures.

Insufficient Cooling Diagnosis

Step

Action

Value(s)

Yes

Did you preform a diagnostic system check?

Go to Step 2

Go to Diagnostic System Check in HVAC Systems - Automatic

Park the vehicle inside or in the shade. The ambient temperature must be at least 16° C (60° F).
Open the windows and the doors in order to ventilate the interior of the vehicle.
If the engine is at operating temperature, allow the engine to cool.
Ensure that the ignition key is in the OFF position.
Remove the LH diagonal brace. Refer to Front Fender Upper Diagonal Brace Replacement in Body Front End.
Remove the cross vehicle brace, if equipped. Refer to Cross Vehicle Brace Replacement in Body Front End.
Connect the J 39500-B .
Record readings of the low and high side STATIC pressures.

The low and high side pressure readings should be almost equal to each other once the system has come to rest.

Are both the low and high side pressures above the specified value ?

345 kPa (50 psi)

Go to Step 3

Go to Leak Testing

Start the engine.
Vent the engine exhaust.
Turn the A/C ON.
Visually inspect under the hood to see if the A/C compressor clutch is engaged.

Does the compressor clutch engage ?

Go to Step 4

Go to Powertrain Control Module Controlled Air Conditioning (A/C) Circuit Diagnosis in Engine Controls - 3.1L or Powertrain Control Module Controlled Air Conditioning (A/C) Circuit Diagnosis in Engine Controls - 3.8L

Turn the engine OFF.

Important: Record the relative humidity and the ambient temperature AT THE TIME OF THE TEST.

Record the ambient temperature at the vehicle.
Record the relative humidity, using one of the following methods:

•	Use a psychrometer

•	Consult the local weather bureau

Open all the vehicle doors and windows.
Set the HVAC control assembly to the following positions:

•	To recirculation (RECIR)

•	The blower control (speed) to the highest position

•	The HVAC control assembly to discharge air through the I/P outlets

•	The temperature control(s) to the coldest position(s)

•	Turn the A/C ON

Open the IP air outlet deflectors
Place a thermometer in the I/P left center air outlet.
Place a thermometer in the I/P right center air outlet.
Place the transaxle in PARK and start the engine and elevate the engine RPM to 2000 and maintain.
Operate the A/C system until the outlet temperature reaches the lowest temperature (approximately 5 minutes).
Record the following information:

•	The IP outlet air temperatures

•	The low-side pressure

•	The high-side pressure

Turn the engine OFF and compare the low and high side pressures and the IP output temperatures to the A/C Performance table below.

Does all the recorded data fall within the specified ranges of the A/C Performance table below?

Go to Step 10

Go to Step 5

If the pressures and temperatures recorded DO NOT fall within the specified ranges:

Start the engine and continue to operate the A/C system for an additional 5 minutes.
Record the pressures and temperatures again.
Turn the engine OFF and compare the low and high side pressures and the output temperatures to the A/C Performance table below.

Does all the recorded data fall within the specified ranges of the A/C Performance table below?

Go to Step 10

Go to Step 6

Compare the recorded pressures to A/C System Pressure-Zone Classification .

Do both the low and high side pressures fall within Zone A on the chart?

Go to Cooling Insufficient - Air Conditioning (A/C) System - Pressure Zone A

Go to Step 7

Do the pressures fall within Zone B?

Go to Cooling Insufficient - Air Conditioning (A/C) System - Pressure Zone B

Go to Step 8

Do the pressures fall within Zone C?

Go to Cooling Insufficient - Air Conditioning (A/C) System - Pressure Zone C

Go to Step 9

Do the pressures fall within Zone D?

Go to Cooling Insufficient - Air Conditioning (A/C) System - Pressure Zone D

Go to Step 10

Operate the system in order to verify the repair.

Did you correct the condition?

Go to Step 11

Go to A Diagnostic System Check in HVAC System - Manual or Diagnostic System Check in HVAC System - Automatic

Disconnect the J 39500-B .
Install the LH diagonal brace. Refer to Front Fender Upper Diagonal Brace Replacement in Body Front End.
Install the cross vehicle brace, if equipped. Refer to Cross Vehicle Brace Replacement in Body Front End.

Is the action complete?

System OK

A/C System Pressure-Zone Classification

A/C Performance Table

Relative Humidity	Ambient Air Temperature		Maximum Low Side Pressure		Engine Speed	Maximum Right Center Air Outlet Temperature		Maximum High Side Pressure
%	°F	°C	PSI	kPa	RPM	°F	°C	PSI	kPa
20	70	21	37	255	2000	46	8	225	1551
	80	27	37	255		47	8	275	1896
	90	32	37	255		53	12	325	2241
	100	38	38	262		54	12	325	2241
30	70	21	37	255	2000	48	9	240	1655
	80	27	37	255		50	10	285	1965
	90	32	39	269		57	14	340	2344
	100	38	43	296		60	16	360	2482
40	70	21	37	255	2000	49	9	260	1793
	80	27	37	255		53	12	305	2103
	90	32	42	290		60	16	355	3137
	100	38	49	338		66	19	395	2724
50	70	21	37	255	2000	51	11	275	1896
	80	27	39	269		56	13	320	2206
	90	32	46	317		63	17	375	2586
	100	38	55	379		72	22	430	2965
60	70	21	37	255	2000	53	12	290	2000
	80	27	42	290		59	15	340	2344
	90	32	49	338		66	19	390	2689
	100	38	60	414		78	26	445	3068
70	70	21	37	255	2000	55	13	305	2103
	80	27	45	310		62	17	355	2448
	90	32	53	365		70	21	405	2792
80	70	21	41	283	2000	56	13	320	2206
	80	27	48	331		65	18	370	2551
	90	32	57	393		73	23	420	2896
90	70	21	45	310	2000	58	14	335	2310
90	80	27	52	359	2000	68	20	385	2655