DTC 09

Circuit Description:

In the C.C.O.T. air conditioning system, a cycling low side pressure switch informs the HVAC programmer (via the CCM) of the direct operating condition of the compressor, (cycling). When the refrigeration system becomes low on freon, the "ON/OFF" frequency of the cycling switch increases. If compressor "ON" time becomes too short, the programmer will trip a flag (flash LED) and shut the compressor "OFF" until system is recharged/repaired and battery reset.

Test Description:

Number(s) below refer to circled number(s) on the diagnostic chart.

Important
^ It is possible that the A/C programmer logic could be lost if the 15 amp Courtesy (CTSY) fuse the 10 amp radio fuse or the negative battery cable are installed with the ignition in the "ON" position. Logic can he restored by clearing system memory.
^ If Code 9 is cleared but compressor still won't engage, it is possible that ECM Codes 66, 67, 68 or 69 are present. If any of these codes are present, refer to Computers and Control Systems for diagnosis.

1. This validates the need for further system testing by removing the negative battery cable and installing after 1 minute to clear a possible false code.
2. Code 09 indicates the A/C system is low on refrigerant 12. Add one pound and leak check system. If no leak is found, proceed to Step 3.
3. This step will charge system as necessary so clutch cycles can be monitored. Excess cycling is usually due to a plugged orifice if system is properly charged. If clutch will not engage, jump the pressure cycling switch to check for an open.

Diagnostic Aid:

If A/C system pressures are in range after referring to HVAC diagnosis and Code 09 is still present, refer to Computers and Control Systems. Testing and Inspection