Automatic Temp Control

031 B1251 IN-CAR TEMPERATURE SENSOR OPEN GO to Pinpoint Test B
PINPOINT TEST B: IN-CAR TEMPERATURE SENSOR INOPERATIVE B1 CHECK SENSOR RESISTANCE

NOTE: An open sensor will cause warm air discharge at 18°F (65° C) setting. A shorted sensor will cause cool discharge air at 29°F (85°C) setting.

• Disconnect the A/C ambient air temperature sensor.
• Using an ohmmeter, measure the resistance across the sensor terminals and compare the readings with the following sensor resistance table:
  
  Approximate Temperature Sensor Resistance Acceptance Range 10-20°C (50-68°F) 37K-58K ohms 20-30°C (68-86°F) 24K- 37K ohms 30-40°C (86-104°F) 16K-24K ohms

Are resistance values within the specified limits?
Yes No GO to B2 . REPLACE A/C ambient air temperature sensor and bracket. RESTORE vehicle. RETEST system. B2 CHECK ASPIRATOR INSTALLATION

• Gain access to automatic temperature control sensor.
• Check for proper installation of automatic temperature control sensor hose and elbow.

Is aspirator installed properly and hose connected?
Yes No GO to B3 . SERVICE automatic temperature control sensor hose and elbow as necessary. RESTORE vehicle. RETEST system. B3 CHECK CIRCUIT 470 (PK/BK) AT AUTOMATIC TEMPERATURE CONTROL SENSOR

• Turn ignition switch to the RUN position.
• Turn EATC module to NORM A/C position.
• Disconnect automatic temperature control sensor.
• Using a voltmeter, check Circuit 470 (PK/BK) for voltage at sensor connector.

Is voltage 5 volts?
Yes No GO to B5 . GO to B4 . B4 CHECK CIRCUIT 470 (PK/BK) FOR OPEN

• Disconnect connector C227 at EATC module.
• Using an ohmmeter, check Circuit 470 (PK/BK) between EATC module and automatic temperature control sensor for open.

Is there 5 ohms or less?
Yes No SERVICE Circuit 470 (PK/BK) for open. RETEST system. GO to B5 . B5 TEST CIRCUIT 470 (PK/BK) FOR SHORT

• Using an ohmmeter connected to a good ground, connect other lead to EATC module connector Pin C227 , Circuit 470 (PK/BK).

Is resistance less than 10,000 ohms?
Yes No SERVICE Circuit 470 (PK/BK) for short. RESTORE vehicle. RETEST system. GO to B6 . B6 TEST CIRCUIT 790 (W/O) FOR OPEN

• Using an ohmmeter, connect one lead to EATC module connector Pin C227 , Circuit 790 (W/O) and other lead to automatic temperature control sensor Circuit 790 (W/O).

Is resistance 5 ohms or less?
Yes No GO to B7 . SERVICE Circuit 790 (W/O). B7 TEST CIRCUIT 790 (W/O) FOR SHORT

• Using an ohmmeter connected to a good ground, connect other lead to EATC module connector Pin C227 , Circuit 790 (W/O).

Is resistance less than 10,000 ohms?
Yes No SERVICE Circuit 790 (W/O) for short. RESTORE vehicle. RETEST system. REPLACE EATC module. RESTORE vehicle. RETEST system.

Do you hear any clicking sounds coming from behind the instrument panel ? Electrically controlled actuators move temp . blend doors and they wear out .Plastic gears etc..
Electronic Automatic Temperature Control System
The electronic automatic temperature control (EATC) system operation is determined by the settings on the EATC module. The EATC system automatically maintains a selected temperature for vehicle interior comfort, including capabilities to maintain separate temperature settings for the driver and front passenger. The electronic temperature control capabilities are achieved by splitting the air distribution system internally and utilizing 2 individually operated temperature blend doors. The EATC system is composed of the EATC module, automatic temperature control (ATC) solenoid and manifold, blower motor speed control, 4 vacuum control motors, 2 temperature blend door actuators, in-car temperature sensor, ambient air temperature sensor and solar amplifier (sunload sensor) to control the various functions. Do you know about DTC'S - diagnostic trouble codes ?

The electronic automatic temperature control (EATC) system must be diagnosed by first retrieving any DTCs, if present.

• An on-demand (hard fault) DTC indicates that the fault is currently present. An on-demand DTC suggests a wiring fault, disconnected connector or component failure.
• A continuous (intermittent) DTC alone (corresponding on-demand DTC is not present) indicates that the fault is an intermittent condition and may not be currently present. A continuous only DTC suggests a poor wiring connection, loose pin or terminal or intermittent component failure.

On-demand (hard fault) or continuous (intermittent fault) DTCs can be retrieved using a diagnostic tool. If using a diagnostic tool, refer to the diagnostic tool operating manual.
On-demand DTCs can also be retrieved by carrying out the Electronic Automatic Temperature Control Module On-Demand Self Test. To retrieve and/or clear continuous DTCs carry out the Electronic Automatic Temperature Control Module - Retrieve Continuous DTCs procedure. Always carry out the Electronic Automatic Temperature Control Module On-Demand Self Test before retrieving continuous DTCs.
If no DTCs are present, GO to Symptom Chart for the appropriate diagnostic action.

DTC EATC DTC Displayed Notes Description Action to Take B2266 2266 N/A LH Blend Door Failure or Short Go To Pinpoint Test A . B2267 2267 EATC Only RH Blend Door Failure or Short Go To Pinpoint Test A .

• The dual temperature control is inoperative/does not operate correctly - Dual Zone EATC

• Temperature blend door/actuator broken/binding
• EATC module

• CHECK the temperature blend doors/actuators for a binding or broken condition. If no condition is found, INSTALL a new EATC module. REFER to Section 412-01 . TEST the system for normal

No. The engine temp sensor affects engine idle speed, and timing. There is an in car temp sensor that controls the position of the blend door and the fan speed if the system has automatic temperature control.It also cycles the AC compressor clutch and the radiator cooling fans.

First check your coolant level. If the coolant system is full, then it is probably the passage doors inside the heater/AC case not operating properly. A door or its actuator has a malfunction. Most actuators are vacuum controls, although some are electric motor operated. Turn Heater on and set temp. control on high-this should cause the actuators to respond by opening some inner doors. So when you turn the blower on, air is forced across the heater core (the little coolant filled "radiator" in the case), and warm air comes out the vents. Watch or listen for the actuators to respond when you use the heater controls. There may be several actuators on the heater case, situated all around, but they are on the outside of the case, right near the inner door they operate.

sounds like you have a temp door motor problem on the drivers side. the motors seize/stick and have to be replaced.

If you have an automatic climate system where you can set temp the the compressor will run at some of the middle settings. The system blends cold and warm air to obtain the desired temp setting. If it does not have automatic control you have another issue.

The blower and temperature controls are independent if you have the manual system but they are integrated in the control head for the automatic version. The automatic version does not include a set of resistors. Do you know which system you have? If you have manual controls, I recommend you test the resistor with an ohmmeter. It's possible that your blend door actuator and resistor have failed independently. However, if you have the automatic system, your theory is as good as any. By the way, your wiring diagrams are available on autozone.com--they include both manual and automatic system schematics.

Is this an automatic temp. control or manual heater control? if it's automatic control,it can be an expensive circuit board which has gone bad. don-ohio

Hello: Check the temperature door. Make sure it is in the heat position. The temp door should be on the passenger side under the dash, remove the cover and with key on move the temp control from heat to cool. If the temp control is manual there will be a cable that is connected to the arm that moves the door. If the system is automatic there will be a electric actuator that moves the door.

What year is the vehicle ? The A/C button on the control panel is a direct input to the PCM /ECM - engine computer . The PCM/ECM energizes the compressor clutch relay to engage the compressor .