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 for diagnostics.

Follow the visual inspection procedure below and refer to the Diagnostic Trouble Code Index for electrical faults.

Information about the system and its operation can be found in the relevant section of the service station manual.

Inspection and verification

1. Ensure that the customer's complaint is justified.

2. Visually inspect for obvious mechanical and electrical problems.

Mechanical factors	Electrical factors
Blockage/reduction of flow capacity of intake channels Coolant level Air penetration into the cooling system Electric motors and distribution valves	Fuses and fuses Wiring harnesses and electrical connectors Fan Motor Relay Fan control module Blower fan assembly Automatic temperature control module

The article was copied from the website LRMAN.ru

3. If an obvious cause for the problem you identified or the customer described is found, resolve it before proceeding with further actions. (if possible).

4. Use the approved diagnostic system or scan tool to retrieve all diagnostic trouble codes (DTCs) before referring to the Symptom Chart and DTC Index.

Clear all DTCs after troubleshooting.

Table of signs of malfunction

Sign of malfunction	Possible reasons	Actions
The air intake system is stuck in one position	Sensor malfunction Distribution motor failure	Check for DTCs indicating a faulty sensor. (refer to the DTC Index below.). Perform a self-test of the timing motor. Refer to the relevant section in the workshop manual.
Increased noise from the blower fan	Mechanical failure of the blower fan Dirt getting into the blower fan Solar radiation sensor malfunction	Check for mechanical faults/dirt in the fan motor or mounting components. Check for diagnostic trouble codes (DTCs) indicating a sensor fault.
Inability to control air flow or temperature	Distribution motor malfunction(s) Control module failure	Perform a self-test of the distribution motor. Refer to the corresponding section in the service station manual. Check for DTC codes that indicate a malfunction of the module (refer to the DTC Index below.).
Lack of hot air	Cooling system malfunction Fan lock with viscous coupling Distribution motor malfunction(s) Control module failure	Check the coolant level, the operation of the visco-coupling fan, etc. Perform a self-test of the distribution motor. Refer to the corresponding section in the service station manual. Check for DTC codes that indicate a malfunction of the module (refer to the DTC Index below.).

DTC Index

NOTE: Generic scan tools cannot read the codes listed 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 fault. (the last 2 digits provide additional information readable by a manufacturer approved diagnostic system).

NOTE: For a complete list of climate control system DTCs, refer to the Controls section of the service manual.

DTC codes	Description	Possible reasons	Actions
B1A5911	Sensor power supply 5V	Outside Air Temperature Sensor 5V Power Supply Circuit Short to Ground	According to the electrical manual, check the outside air temperature sensor circuit. Refer to the guided diagnostic routine for this code on the approved diagnostic system.
B1A6312	Right solar radiation sensor	Right Solar Radiation Sensor Signal Circuit: Short to 5V	According to the electrical manual, check the right solar radiation sensor signal circuit. Refer to the guided diagnostic routine for this code on the approved diagnostic system.
B1A6412	Left solar radiation sensor	Left Solar Radiation Sensor Signal Circuit: Short to 5V	According to the electrical manual, check the left solar radiation sensor signal circuit. Refer to the guided diagnostic routine for this code on the approved diagnostic system.
B1B6013	Feedback potentiometer electrical circuit	The air intake system is stuck in one position Feedback Potentiometer Circuit: High Resistance	Check the air temperature mode motor/feedback potentiometer circuits. Refer to the electrical manual.
B1B6711	Air intake servo potentiometer electrical circuit	Evaporative Coolant Recirculation Motor Signal Circuit Short to Ground	Check the air intake motor circuit. Refer to the electrical manual. Refer to the guided diagnostic routine for this code on the approved diagnostic system.
B1B6715	Air intake servo potentiometer electrical circuit	Recirculation Motor Signal Circuit High Resistance Recirculation motor signal circuit: short circuit to battery +	Check the air intake motor circuit. Refer to the electrical manual. Refer to the guided diagnostic routine for this code on the approved diagnostic system.
B1B6801	Air intake system servo motor	Recirculation motor malfunction	Check the air intake motor circuit. Refer to the electrical manual. Refer to the guided diagnostic routine for this code on the approved diagnostic system.
B1B7400	Footwell/Windshield Air Distribution Flap Actuator	Mechanical failure of the actuator Overheating of the actuator Actuator circuit: high resistance Actuator electrical circuit: short circuit Power failure of the actuator	Check for mechanical faults in the footwell/windshield air distribution flap motor (see visual inspection). Refer to the guided diagnostic program for this code on the approved diagnostic system.
B1B7449	Footwell/Windshield Air Distribution Flap Actuator	Internal actuator failure	Check the operation of the footwell/windshield air distribution flap motor. Refer to the guided diagnostic routine for this code on the approved diagnostic system.
B1B7700	Stepper motor for drive of front right mixing flap	Mechanical failure of the actuator Overheating of the actuator Actuator circuit: high resistance Actuator electrical circuit: short circuit Power failure of the actuator	Mechanical faults of the right mixing flap drive motor (see visual inspection). Refer to the guided diagnostic program for this code on the approved diagnostic system.
B1B7749	Stepper motor for drive of front right mixing flap	Internal actuator failure	Refer to the guided diagnostic program for this code on the approved diagnostic system.