Diagnostics and testing of heating and ventilation (Discovery 3)

Review

The heating and ventilation system has a fairly simple design that does not require any specialized methods to perform diagnostics.

Follow the visual inspection procedure below and refer to the Electrical Diagnostic Trouble Code Index.

Information about the system and its operation can be found in the appropriate section of the workshop manual.

Inspection and verification

1. Make sure the customer's complaint is valid.

2. Visually inspect for obvious mechanical and electrical problems.

Mechanical factors	Electrical Factors
Clogged/reduced inlet capacity coolant level Air intrusion into the cooling system Electric motors and distribution dampers	Fuses Wiring harnesses and electrical connectors Fan Motor Relay Fan control module Blower fan assembly Automatic temperature control module

3. If there is an obvious cause for the problem you identified or the customer described, fix it before proceeding with the next steps (if possible).

4. Use an approved diagnostic system or scan tool (tester), to retrieve all DTCs before referring to the Symptom Table DTC Index (DTC).

Clear all DTCs after troubleshooting.

Symptom table

Symptom	Possible reasons	Actions
Air intake system stuck in one position	Sensor failure Distribution motor malfunction	Check for DTCs indicating sensor failure (refer to the DTC Index below). Perform a distribution motor self-test. Refer to the relevant section in the workshop manual.
Increased fan noise	Mechanical failure of the blower fan Dirt in the blower Solar sensor malfunction	Check for mechanical failures/dirt in the electric fan or fasteners. Check for DTCs (DTC), indicating a sensor failure.
Inability to control air flow or temperature	Malfunction (And) distribution motor Control module failure	Perform a distribution motor self-test. Refer to the relevant section in the workshop manual. Check for DTCs indicating module failure (refer to the DTC Index below).
No hot air	Cooling system failure Viscous fan lock Malfunction (And) distribution motor Control module failure	Check coolant level, viscous fan operation, etc. Perform a distribution motor self-test. Refer to the relevant section in the workshop manual. Check for DTCs indicating module failure (refer to the DTC Index below).

DTC index

NOTE: Universal Scan Tools cannot read the listed codes or can only read 5-digit codes. Match the 5 digits from the scan tool with the first 5 digits of the listed 7 digit code to identify the problem (the last 2 digits give additional information read by the diagnostic system approved by the manufacturer).

NOTE: For a complete list of climate control DTCs, see "Elements of the control system" manuals for service stations.

DTCs	Description	Possible reasons	Actions
B1A5911	Sensor power supply 5 V	Ambient air temperature sensor 5 V supply circuit - short circuit to ground	Check the outdoor air temperature sensor circuit according to the electrical manual. Refer to the guided diagnostic program for this code on the approved diagnostic system.
B1A6312	Right solar radiation sensor	Right Solar Sensor Signal Circuit Short to 5V	Check the right solar sensor signal circuit according to the electrical manual. Refer to the guided diagnostic program for this code on the approved diagnostic system.
B1A6412	Left solar sensor	Left Solar Sensor Signal Circuit Short to 5V	Check the left solar radiation sensor signal circuit according to the electrical manual. Refer to the guided diagnostic program for this code on the approved diagnostic system.
B1B6013	Feedback potentiometer circuit	Air intake system stuck in one position Feedback potentiometer circuit high resistance	Check air temperature mode motor/feedback potentiometer circuits. Refer to the electrical manual.
B1B6711	Air intake servo potentiometer circuit	Recirculation Motor Signal Circuit Short to Ground	Check the air intake motor circuit. Refer to the electrical manual. Refer to the guided diagnostic program for this code on the approved diagnostic system.
B1B6715	Air intake servo potentiometer circuit	Recirculation motor signal circuit high resistance Recirculation Motor Signal Circuit Short to Battery	Check the air intake motor circuit. Refer to the electrical manual. Refer to the guided diagnostic program for this code on the approved diagnostic system.
B1B6801	Air intake servo motor	Recirculation motor malfunction	Check the air intake motor circuit. Refer to the electrical manual. Refer to the guided diagnostic program for this code on the approved diagnostic system.
B1B7400	Actuator of the air distribution damper in the legs / on the windshield	Mechanical failure of the actuator Overheating of the actuator Actuator circuit high resistance Actuator circuit short circuit Actuator power failure	Check for mechanical faults in the foot/windshield air distribution damper motor (see visual inspection). Refer to the guided diagnostic program for this code on the approved diagnostic system.
B1B7449	Actuator of the air distribution damper in the legs / on the windshield	Internal malfunction of the actuator	Check the operation of the foot/windshield air distribution damper motor. Refer to the guided diagnostic program for this code on the approved diagnostic system.
B1B7700	Stepper motor drive front right mixing damper	Mechanical failure of the actuator Overheating of the actuator Actuator circuit high resistance Actuator circuit short circuit Actuator power failure	Mechanical malfunctions of the electric motor of the drive of the right mixing damper (see visual inspection). Refer to the guided diagnostic program for this code on the approved diagnostic system.
B1B7749	Stepper motor drive front right mixing damper	Internal malfunction of the actuator	Refer to the guided diagnostic program for this code on the approved diagnostic system.