A/C - Inop/Defrost Mode Indicator/False Diagnostics
Bulletin No.:T-93-55
File in Group:
1
Number:
95
Corp.Ref.No.:
231214
Date:
Jan. 1993
SUBJECT:
A/C INOPERABLE/DEFROST MODE INDICATOR/FALSE DIAGNOSTICS
MODELS AFFECTED:
1993 FLEETWOODS (RWD) BUILT PRIOR TO VIN BREAKPOINT PR704043
Some 1993 Fleetwoods (RWD) may experience one or more of the following conditions:
1. A/C may become inoperative due to the compressor clutch not engaging as a result of setting a diagnostic code 9 or 109 (low freon).
2. The defrost symbol located on the air control head display may remain lit when the system has returned to the automatic mode.
3. Five diagnostic codes (23, 25, 26, 41, and 46) will display incorrect information on the A/C control head as referred to in the Service Information Manual.
4. The A/C control assembly can skip "21~ C" when toggling through the temperature range up or down. "21~ C" may be displayed when the vehicle is started under the Fahrenheit setting and subsequently switching over to Celsius.
These conditions may be caused by the following:
1. Under certain during maneuvers the power steering cut off switch can cause a false diagnostic code 9 or 109 to be stored.
2. While in auto mode and at a selected temperature setting of 6O~F or 90~ F if defrost mode is selected and a different temperature setting is selected, the system may revert back to the auto mode.
To correct these conditions perform the appropriate repair as indicated below:
NOTE:
Replace the A/C control assembly for conditions 1 and/or 2. DO NOT replace the A/C control assembly for conditions 3 and/or 4. The Eve correct ECM diagnostic codes are readable by the use of an off-board tool such as CAMS or Tech 1.
Condition 1:
Perform the fault code 9/109 low freon detected A/C performance check as outlined in the attached diagnostic flow chart. Perform repairs if necessary. Replace the A/C control head per Service Information Manual, Section 1C. Use new P/N 16184133.
Condition 2:
If this condition can be forced on a vehicle as outlined by performing Cause 2, replace the A/C control assembly per Service Information Manual, Section 1C. Use new P/N 16184133.
Conditions 3 and 4:
If the A/C control assembly is replaced as outlined in correction 1 or 2, the new assembly (P/N 16184133) will give the vehicle the ability to display all ECM diagnostic codes and 21~C.
Figures 1 and 2
Circuit Description:
In the CCOT air conditioning system, the pressure cycling switch assembly informs the HVAC control assembly of the direct operating condition (cycling) of the compressor assembly. When the refrigeration system becomes low on freon, the on/off frequency of the pressure cycling switch assembly increases, Low freon events can be monitored by displaying parameter "-29". The ECM measures this frequency through circuit 67 and sends this information to the HVAC control assembly via circuit 800. The HVAC control assembly will disable the compressor assembly when a low freon condition is detected. The compressor assembly will remain disabled until DTC 09 or 109 is cleared from the HVAC control assembly memory. The pressure cycling switch assembly status is monitored for a low freon condition only at vehicle speeds above 8 km/h (5 mph). This is to ensure proper air flow through the condenser assembly and engine compartment for an accurate reading.
NOTICE:
Compressor assembly damage may occur if the compressor assembly is operated with low freon, no freon or no refrigerant oil.