2. With the engine running, set the air conditioner control to the lowest temperature and turn the fan to the highest speed.
3. Ask an assistant to press the air conditioner power button while you observe the compressor. The clutch should make an audible click and the compressor should begin to rotate. If the compressor does not start, turn off the engine and disconnect the air conditioner pressure sensor. Short the sensor connector terminals with a jumper and try to turn on the air conditioner again (see Figure 14.12). If the compressor now starts working, then the pressure in the system is too high or too low. Have your system tested by a specialist.
Note: On Mazda models from 1993-1995, the A/C pressure sensor is located in the refrigerant line leading to the receiver-drier (not on the receiver itself). This pipe with the sensor is located between the front bumper and the radiator.
4. If the clutch does not engage, check at its connector whether battery voltage is supplied to the clutch when the air conditioner is turned on. If voltage is present at the clutch connector, turn off the ignition and disconnect the compressor electrical connector. Apply positive voltage from the battery directly to the clutch connector contact using a jumper wire. If the clutch still does not engage, it is faulty and must be replaced.
5. If there is no voltage at the clutch connector, check the integrity of the corresponding fuses in the passenger compartment and under the hood. If the fuses are good, remove the A/C relay from the underhood fuse and relay box. Check the relay as indicated in chapter 12.
6. After removing the relay, turn on the ignition and check if battery voltage is supplied to terminals 3 and 5 of the air conditioner relay in the fuse/relay box (figure 15.6). There should be voltage on both contacts. Short-circuit contacts 2 and 3 with a jumper and listen to see if the clutch engages.
7. If the clutch still does not engage, and the relay, fuses and the clutch itself are good, check for an open in the circuit between the relay box and the clutch connector. If the circuit is OK, check the integrity of the circuit between the ECU and the relay box. If this chain is also intact, send it to the control unit for inspection.