Manual Three Zone Temperature Control

B1012-Defrost Switch Request Input Circuit/Performance

For a complete wiring diagram, refer to.

Theory of Operation

The HVAC A/C Heater Control contains various switches and knobs that are used to change the systems operation. Many of the switches are momentary switches which are normally open or in the Off position and the status changes when the switch button or knob is pushed or turned. An active DTC indicates that the switch is stuck in an On position. A stored DTC indicates that the switch was stuck in a On position for more than 120 seconds but has since returned to its normal state of Off.

• When Monitored: With the ignition on.

• Set Condition: If the Defrost mode switch is stuck in an On position for more than 120 seconds. This DTC has a de-maturing time of two seconds. If the DTCs status changes from active to stored, the DTC will stay in memory for 100 ignition cycles.






Always perform the HVAC Pre-Diagnostic Troubleshooting procedure before proceeding. Refer to => Non-DTC Based
Diagnostics. HVAC Pre-Diagnostic Troubleshooting Procedure

Test Step 1 - INSPECT FOR OBJECT HOLDING SWITCH IN AN ON POSITION

• Inspect the A/C Heater Control for an object or debris holding the Defrost mode switch in an On position.

• Using the scan tool you can read the On/Off status of the control switch.

Is the Defrost mode switch being held in or stuck in an On?

Yes

• Clean or repair the A/C Heater Control as necessary. If you are unable to clean the switch to where the switch can work properly, replace and program the A/C Heater Control.

• Perform the HVAC Verification Test. Refer to => Non-DTC Based Diagnostics. HVAC Verification Test

No

• Go to Test Step 2 => [ Test Step 2 - A/C HEATER CONTROL ]

Test Step 2 - A/C HEATER CONTROL

• Turn the ignition on.

• With the scan tool, erase HVAC DTCs.

• Turn the ignition off for 10 seconds, and then turn the ignition on and wait a minimum of 120 seconds.

• With the scan tool, read HVAC DTCs.

Does the scan tool display this DTC as Active or is the status of the switch reading On?

Yes

• Replace and program the A/C Heater Control.

• Perform the HVAC Verification Test. Refer to => Non-DTC Based Diagnostics. HVAC Verification Test

No

• Test complete.

• Perform the HVAC Verification Test. Refer to => Non-DTC Based Diagnostics. HVAC Verification Test