Heater Core Sensor Replacement (80/03/96/US)

Publication date: 1996-12-06
Reference number: 80/03/96/US

HEATER CORE SENSOR REPLACEMENT

TECHNICAL SERVICE BULLETIN

Reference Number(s): 80/03/96/US, Date of Issue: December 6, 1996

LAND ROVER:	Range Rover 4.0/4.6
AFFECTED VEHICLES:	LP Up to TA344173

DETAIL

There has been a reliability concern identified with the heater core sensor. A faulty heater core sensor may cause abnormal air distribution or temperature control.

Proper diagnosis of the heater core sensor is to be carried out as per the Operation Pride HVAC specification document. The sensor may have faulty soldering which will cause an open circuit or inaccurate temperature measurement.

The sensor supplier has remedied the issue and parts stock contains only reliable sensors.

The diagnostic steps and repair procedures detailed below were developed as an element of the Land Rover Way Operation PRIDE. This TIB provides a library location for PRIDE information within the Land Rover North America technical literature system.

ACTION REQUIRED

Replacement of faulty heater core sensor

PARTS INFORMATION

STC 3256 Heater Core Sensor

PROCEDURE

Perform TestBook troubleshooting to determine if DTC 49 or DTC 50 is present.

NOTE: If there is a fault in the heater core sensor circuit that causes hot air from the vents, selecting LO/LO will result in cold air. Diagnose the fault as detailed below:

(DTC 49) Check for continuity between C221 pin 2 and C246B pin 2 (signal).
(DTC 49) Check for short to +12V between C221 pin 2 and C246B pin 2 (signal).
(DTC 50) Check for short to ground between C221 pin 2 and C246B pin 2 (signal).

If trouble codes or symptoms indicate heater core sensor fault, follow the instructions for removal and replacement.

REMOVAL

Open glove box. Remove 5 screws securing glove box liner to fascia. See Fig 1 .

Fig 1: Lowering Glove Box Liner
Lower glove box liner. Release 2 clips to disengage glove box release cable latch from location.
Locate heater core sensor on inlet pipe of heater core.
Disconnect heater core sensor from pipe and disconnect heater core sensor multiplug. See Fig 2 .

Fig 2: Disconnecting Heater Core Sensor & Heater Core Sensor Multiplug

Fig 3: Test Procedure 3: Solar Sensor & Temperature Sensor Circuits
Check for continuity between C221 pin 1 and C246B pin 10 (reference ground).

Check sensor resistance at ambient temperature.

SENSOR RESISTANCE

Temperature	Heater Core Resistance (kohm)
-20°C (-4°F)	271.2
-10°C (14°F)	158.0
0°C (32°F)	95.0
10°C (50°F)	58.7
20°C (68°F)	37.3
30°C (86°F)	24.3
40°C (104°F)	16.1

If the problem is intermittent, check the build date number stamped on the top of sensor. The last two digits should be 46, 56, 66, or higher (46 corresponding to 4/96). If sensor has a build date prior to 4/96, it may be faulty.
If any of the above tests and inspections indicate a faulty sensor, replace the sensor with STC 3256.

REPLACEMENT

Refit sensor to heater core inlet tube.
Reconnect heater core sensor multiplug to vehicle harness.
Refit glove box release cable latch.
Refit glove box liner to fascia and secure with 5 screws.

WARRANTY

Normal warranty policy and procedures apply.

WARRANTY CLAIMS INFORMATION

SRO	Description	Time
82.20.94	Heater core sensor renew	0.35 hr.