For 1990-2009 cars

Table 1: | Quick Look-Up Troubleshooting Table
Table 2: | R-134a Temperature/Pressure Parameters

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 |

1. Connect the scan tool.
2. Read the scan tool for diagnostic codes.

Were diagnostic codes found?

--

Go to Step 19

Go to Step 2

2 |

1. Turn the ignition switch to ON.
2. Turn the blower speed from the following positions:

• | OFF to LO

• | MED LO to MED HI

• | HI

• | Then back to OFF

3. Turn the ignition switch to LOCK.

Does the blower motor speed increase at each speed level when blower speed selector switch is turned to HI and then decreases as the switch is moved towards LO?

--

Go to Step 3

Go to Step 20

3 | Inspect for a loose, damaged or missing compressor drive belt. Is the action complete? | -- | Go to Step 4 | --
4 | Inspect the engine coolant fan operation. Is the action complete? | -- | Go to Step 5 | --
5 |

1. Inspect the condenser for restricted air flow.
2. Clean and/or repair as necessary.

Is the action complete?

--

Go to Step 6

--

6 |

1. The ambient air temperature must be at least 16°C (60°F) before continuing to next step.
2. Start the engine.
3. Set the air mode to VENT.
4. Set the blower speed to HI.
5. Set the temperature mode to full COLD.
6. Press the A/C switch to ON.

Does the compressor clutch engage?

--

Go to Step 7

Go to Step 9

7 |

1. Closely monitor the compressor for unusual knocking or loud moaning noises and/or compressor drive belt slipping.
2. Cycle the compressor clutch by pressing the A/C mode switch.
3. Notice if compressor drive belt is slipping.

Is the compressor noise excessive?

--

Go to Step 21

Go to Step 8

8 | Feel the liquid line between the condenser and the receiver/dryer. The line should feel warm to the touch. Does the line feel cold? | -- | Go to Step 22 | Go to Step 12
9 |

1. Turn the ignition switch to LOCK.
2. Connect J 39500-B to the service ports.
3. Inspect the system Lo and Hi pressures. Both pressures should be almost equal to each other.

Are both Lo and Hi pressures the same as or higher than specified value?

345 kPa (50 psi)

Go to Step 23

Go to Step 10

10 | Monitor and compare Lo and Hi pressure readings. Are both Lo and Hi pressures the same as or higher than specified value? | 69345 kPa (1050 psi) | Go to Step 22 | Go to Step 11
11 | Inspect the system for refrigerant leaks. Was the refrigerant leak found? | -- | Go to Step 24 | Go to Step 26
12 | Feel the evaporator inlet pipe (small pipe) and evaporator outlet pipe at bulkhead. The evaporator inlet pipe should feel warm to the touch. Does the inlet evaporator pipe feel colder than the evaporator outlet pipe? | -- | Go to Step 13 | Go to Step 16
13 | Inspect the system for refrigerant leaks. Was the refrigerant leak found? | -- | Go to Step 24 | Go to Step 14
14 | Monitor compressor clutch cycle rate. Was the compressor clutch cycle rate more than 8 cycles per minute? | -- | Go to Step 25 | Go to Step 15
15 |

1. Start the engine.
2. The air mode control knob set to VENT.
3. Set the blower speed selector switch to HI.
4. Set the temperature control knob all the way to COLD.
5. Press the A/C mode switch to ON.
6. Feel the evaporator inlet pipe (small pipe) and evaporator outlet pipe at bulkhead again. The evaporator inlet pipe should feel warm to the touch.

Does inlet evaporator pipe feel colder than the evaporator outlet pipe?

--

Go to Step 25

Go to Step 26

16 |

1. Warm the engine to normal operating temperature.
2. Feel the heater inlet hose at engine coolant control valve. It should feel warm but not as hot as engine coolant.

Does the heater inlet hose feel hot?

--

Go to Step 27

Go to Step 17

17 | Inspect HI pressure. Does the compressor engage within specified values? | 196-3140 kPa (28-455 psi) | Go to Step 18 | Go to Step 28
18 |

1. Run compressor and monitor both clutch operation and HI pressure for five minutes.
2. The compressor should disengage when HI pressure is outside specified values.

Did the compressor stay engaged outside specified values?

196-3140 kPa (28-455 psi)

Go to Step 28

Go to Step 29

19 | Refer to Blower Motor Inoperative at Any Speed . Is the action complete? | -- | Go to Step 2 | --
20 | Refer to Blower Motor Inoperative at Any Speed . Is the action complete? | -- | Go to Step 3 | --
21 | Refer to Noise Diagnosis and determine the cause of excessive compressor noise. Is the action complete? | -- | Go to Step 8 | --
22 | Repair restriction in the HI side of the refrigerant system. Visually check for a line/pipe frosty spot to locate restriction. Is the action complete? | -- | Go to Step 12 | --
23 | Correct and/or repair code setting criteria. Is the action complete? | -- | Go to Step 7 | --
24 | Repair the refrigerant leak. Is the action complete? | -- | Go to Step 29 | --
25 |

1. Discharge the system.

Refer to Refrigerant Recovery and Recharging .

2. Inspect for plugged expansion valve or HI side restriction.

Is the action complete?

--

Go to Step 29

--

26 | Evacuate and recharge the system. Refer to Refrigerant Recovery and Recharging . Is the action complete? | -- | Go to Step 29 | --
27 | Inspect the Heater Water Valve for a leaking or constantly-open. Is the action complete? | -- |  | --
28 | Replace the A/C dual pressure switch. Is the action complete? | -- | Go to Step 17 | --
29 | Perform the A/C performance test. Is the action complete? | -- | System OK | --

#### Quick Look-Up Troubleshooting Table

Set controls to: NORMAL mode, HI blower, Lowest °C (°F) setting, Window open
Pressures as compared to a normal operating system
A/C NOT COLD | HI-SIDE PSI | LOW-SIDE PSI | RELATED SYMPTOMS
--- | --- | --- | ---
Undercharge | Low | Low | Compressor Grumbling Heard Inside of Vehicle
TXV Failure or Stuck Closed | Low | Low | Low-side Gauge Fluctuation
Low Side Restriction | Low | Normal to Low | Hose Kinked or Restricted
Engine Cooling Fan(s) Inoperative | High | High | Confirm Operation of Fan and Direction of Rotation
Overcharged | High | High | Compressor Cutting Out Due to High Pressure
Air in System | High | High | Compressor Cutting Out; Evaporator Freeze Up Possible
Restricted Airflow Across Condenser | High | High | Visually Inspect
TXV Stuck Open | High | High | Rapid Pressure Equalization on Shutdown; Slugging Noise Heard from Evaporator on Startup
Clutch/Relay/Electrical Failure | Low | High | Compressor Clutch Does Not Engage/High and Low-Side Pressures are Equal
Internal Compressor Failure | Low | High | No Change ON vs. OFF; High and Low-Side Pressures are equal
High-Side Restriction | Normal to High | Normal to Low | Feel High Side Hose/Piping for Abrupt Drop in Temperature

#### R-134a Temperature/Pressure Parameters

°C | °F | kPa | PSI | °C | °F | kPa | PSI
--- | --- | --- | --- | --- | --- | --- | ---
-9 | 16 |  | 106 | 15 | 38 | 100 |  | 857 | 124
-8 | 18 | 115 | 17 | 39 | 102 | 887 | 129
-7 | 20 | 124 | 18 | 40 | 104 | 917 | 133
-6 | 22 | EVAP. RANGE | 134 | 19 | 41 | 106 | 948 | 137
-4 | 24 | 144 | 21 | 42 | 108 | 980 | 142
-3 | 26 | 155 | 22 | 43 | 110 | COND. RANGE | 1012 | 147
-2 | 28 | 166 | 24 | 44 | 112 | 1045 | 152
-1 | 30 | 177 | 26 | 46 | 114 | 1079 | 157
0 | 32 | 188 | 27 | 47 | 116 | 1114 | 162
1 | 34 | 200 | 29 | 48 | 118 | 1149 | 167
2 | 36 | 212 | 31 | 49 | 120 | 1185 | 172
3 | 38 | 225 | 33 | 50 | 122 | 1222 | 177
4 | 40 | 238 | 35 | 51 | 124 | 1260 | 183
7 | 45 | 272 | 40 | 52 | 126 | 1298 | 188
10 | 50 | 310 | 45 | 53 | 128 | 1337 | 194
13 | 55 |  | 350 | 51 | 54 | 130 | 1377 | 200
16 | 60 | 392 | 57 | 57 | 135 | 1481 | 215
18 | 65 | 438 | 64 | 60 | 140 | 1590 | 231
21 | 70 | 487 | 71 | 63 | 145 | 1704 | 247
24 | 75 | 540 | 78 | 66 | 150 | 1823 | 264
27 | 80 | 609 | 88 | 68 | 155 | 1948 | 283
30 | 85 | 655 | 95 | 71 | 160 | 2079 | 301
32 | 90 | 718 | 104 | 74 | 165 | 2215 | 321
35 | 95 | 786 | 114 | 77 | 170 |  | 2358 | 342