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Heating, Ventilation and Air Conditioning: Overview GMC Savana G2500

Automatic HVAC System 2 illustrations

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. 1: This step determines if the A/C system has at least the minimum refrigerant charge required to operate the system without damage.
  2. 2: This step measures the performance of the A/C system.
  3. 3: This step is to allow for vehicle variations as well as high ambient temperatures.
StepActionValuesYesNo
IMPORTANT: The ambient air temperature must be at least 16°C (60°F). Do not induce additional air flow across the front of the vehicle during the test. If you were sent here from a DTC diagnostic table, clear the DTC upon completion of this test.
1Park the vehicle inside or in the shade. Open the windows in order to ventilate the interior of the vehicle. If the A/C system was operating, allow the A/C system to equalize for about 2 minutes. Turn OFF the ignition. Install the J 43600 ACR 2000 Refrigerant Station. See Special Tools and Equipment . Record the ambient air temperature displayed on the J 43600 . See Special Tools and Equipment . Record the low and high side STATIC pressure readings. Are both the low side and high side pressures within the specified value?More than 16°C (60°F) - 345 kPa (50 psi) More than 24°C (75°F) - 483 kPa (70 psi) More than 33°C (90°F) - 690 kPa (100 psi)Go to Step 2Go to Leak Testing
2IMPORTANT: Record the relative humidity and the ambient air temperature at the time of the test. Close the vehicle doors and windows. Open the drivers door window 12.7-15.2 cm (5-6 inches). Select the following HVAC control settings: The A/C is ON The coldest temperature setting The maximum blower speed Recirculation mode The I/P panel outlet mode All I/P panel outlets are OPEN The passenger side of a Dual Zone HVAC control module is turned OFF The coldest temperature setting on the auxiliary HVAC control assembly The maximum blower speed selected on the auxiliary blower controls Install the temperature probes of the J 43600 in the left and right center panel air outlets. See Special Tools and Equipment . Apply the parking brake. Place the transaxle/transmission in one of the following positions: PARK (Automatic) NEUTRAL (Manual) Start the engine. Operate the A/C system for 5 minutes. Inspect A/C components for the following conditions: Abnormal frost areas Unusual noises IMPORTANT: Press the RESET button, before using the print function of the J 43600 . See Special Tools and Equipment . Print the following information: The panel outlet air temperatures The low-side pressure The high-side pressure Compare the low and high side pressures and the panel output temperatures to the table below. Does all the data recorded fall within the specified ranges of the table below?Go to Step 8Go to Step 3
3If the pressures and temperatures recorded do not fall within the specified ranges: Continue to operate the A/C system for an additional 5 minutes. RESET the J 43600 and record the pressures and temperatures again. See Special Tools and Equipment . Compare the low and high side pressures and the panel output temperature to the table below. Does all the data recorded fall within the specified ranges of the table below?Go to Step 8Go to Step 4
4Do the high and low side pressures fall within the specified ranges, but the panel outlet temperatures do not?Go to Air Conditioning (A/C) Diagnostics - Pressure Zone AGo to Step 5
5Is the low side pressure greater than the specified range, but the high side pressure within or less than the specified range?Go to Air Conditioning (A/C) Diagnostics - Pressure Zone BGo to Step 6
6Are the low and high side pressures both greater than the specified ranges?Go to Air Conditioning (A/C) Diagnostics - Pressure Zone CGo to Step 7
7Is the high side pressure greater than the specified range, but the low side pressure is within or less than the specified range?Go to Air Conditioning (A/C) Diagnostics - Pressure Zone DGo to Step 8
8Operate the system in order to verify the test results. Did you find the same results?System OKGo to Symptoms - HVAC Systems - Manual in HVAC Systems - Manual
IMPORTANT
The ambient air temperature must be at least 16°C (60°F). Do not induce additional air flow across the front of the vehicle during the test. If you were sent here from a DTC diagnostic table, clear the DTC upon completion of this test.
IMPORTANT
Record the relative humidity and the ambient air temperature at the time of the test.
IMPORTANT
Press the RESET button, before using the print function of the J 43600 . See Special Tools and Equipment .

Air Conditioning (A/C) System Performance Test

Ambient Air TemperatureRelative HumidityService Port PressureMaximum Left Center Discharge Air Temperature
Low SideHigh Side
13-18°C (55-65°F)0-100%175-194 kPa (25-28 psi)630-1170 kPa (91-170 psi)7°C (45°F)
19-24°C (66-75°F)Below 40%175-204 kPa (25-27 psi)620-1130 kPa (90-164 psi)7°C (45°F)
Above 40%175-240 kPa (25-35 psi)820-1320 kPa (119-192 psi)10°C (50°F)
25-29°C (76-85°F)Below 35%175-238 kPa (25-35 psi)930-1300 kPa (135-189 psi)10°C (50°F)
35-60%175-249 kPa (25-36 psi)1120-1350 kPa (148-196 psi)11°C (52°F)
Above 60%175-271 kPa (25-39 psi)1100-1450 kPa (160-210 psi)13°C (56°F)
30-35°C (86-95°F)Below 30%184-282 kPa (27-41 psi)1160-1530 kPa (168-222 psi)14°C (57°F)
30-50%194-292 kPa (28-42 psi)1210-1560 kPa (176-226 psi)15°C (59°F)
Above 50%209-307 kPa (30-45 psi)1270-1600 kPa (184-232 psi)17°C (63°F)
36-41°C (96-105°F)Below 20%232-326 kPa (34-47 psi)1430-1790 kPa (208-260 psi)17°C (63°F)
20-40%237-332 kPa (34-48 psi)1440-1770 kPa (209-257 psi)18°C (64°F)
Above 40%247-338 kPa (36-49 psi)1460-1760 kPa (212-255 psi)19°C (66°F)
42-46°C (106-115°F)Below 20%383-367 kPa (41-53 psi)1710-2010 kPa (248-292 psi)20°C (68°F)
Above 20%286-369 kPa (42-54 psi)1710-1960 kPa (248-285 psi)21°C (70°F)
47-49°C (116-120°F)Below 30%327-392 kPa (48-57 psi)1930-2110 kPa (280-306 psi)23°C (73°F)

A/C Performance Table - Front Only

Scheme 3

Scheme 3
Ambient TemperatureRelative HumidityLow Side Service Port PressureHigh Side Service Port PressureMaximum Left Center Discharge Air TemperatureMaximum Left Side Rear Discharge Air Temperature
13-18°C (55-65°F)0-100%175-204 kPa (25-30 psi)360-870 kPa (52-126 psi)12°C (53°F)7°C (45°F)
19-24°C (66-75°F)Less than 40%175-235 kPa (25-34 psi)490-1010 kPa (71-147 psi)12°C (53°F)10°C (50°F)
Greater than 40%175-263 kPa (25-42 psi)620-1120 kPa (90-163 psi)14°C (57°F)12°C (54°F)
25-29°C (76-85°F)Less than 35%177-290 kPa (26-42 psi)870-1270 kPa (126-184 psi)16°C (61°F)14°C (57°F)
35-60%191-295 kPa (28-43 psi)920-1290 kPa (134-187 psi)16°C (61°F)15°C (59°F)
Greater than 60%202-304 kPa (29-44 psi)960-1330 kPa (139-193 psi)17°C (63°F)16°C (61°F)
30-35°C (86-95°F)Less than 30%244-362 kPa (35-53 psi)1160-1590 kPa (168-231 psi)22°C (72°F)19°C (66°F)
30-50%249-358 kPa (36-52 psi)1180-1590 kPa (171-231 psi)21°C (70°F)20°C (68°F)
Greater than 50%255-353 kPa (37-51 psi)1210-1580 kPa (176-229 psi)20°C (68°F)22°C (72°F)
36-41°C (96-105°F)Less than 20%325-441 kPa (47-62 psi)1520-1940 kPa (221-282 psi)28°C (82°F)25°C (77°F)
20-40%323-428 kPa (46-60 psi)1510-1900 kPa (219-276 psi)26°C (79°F)25°C (77°F)
Greater than 40%320-415 kPa (59-73 psi)1510-1860 kPa (219-270 psi)25°C (77°F)26°C (79°F)
42-46°C (106-115°F)Less than 20%407-506 kPa (59-70 psi)1880-2230 kPa (273-324 psi)33°C (91°F)29°C (84°F)
Greater than 20%401-485 kPa (58-70 psi)1860-2160 kPa (270-314 psi)30°C (86°F)30°C (86°F)
47-49°C (116-120°F)Less than 30%466-532 kPa (68-77 psi)2150-2360 kPa (312-343 psi)34°C (93°F)32°C (90°F)

A/C Performance Table - With Rear A/C

Scheme 4

Scheme 4