2003 Honda CRV

Heater problem
2003 Honda CRV 4 cyl All Wheel Drive Automatic 87,000 miles

Regardless of the temerature selected on the control dial, my temperature is either full cold (cold position) or full hot (all other positions). A/C works fine and coolant is obviously circulating. It becomes impossible to comfortably regulate the temperature during the winter. I replaced the Heater Control Valve with no change; the cable from the manual knob moves the cable smoothly.
Eric Powers
December 1, 2009.

Hi Eric Powers,

Try the following to see if you are able to retrieve any trouble codes.


How to Retrieve a Diagnostic Trouble Codes

The Heater Control Panel has a self -diagnosis function. To run the self -diagnosis function, do the following:

1 . Turn the ignition switch OFF.

2 . Turn the fan switch OFF, the temperature control dial on Max Cool and the mode control dial on Vent.

3 . Turn the ignition switch ON (II), then press and hold the recirculation control switch. Within 10 seconds while holding the switch down, press the rear window defogger switch five times. The recirculation indicator blinks two times, then the self -diagnosis will begin. If there is any problem in the system after self -diagnosis is finished, the recirculation indicator will blink the Diagnostic Trouble Code (DTC) 7 through 13. When problems in the evaporator temperature sensor circuit are detected (codes 14 and 15), the A/C indicator will blink the DTC. If no DTC's are found, the indicator will not blink.

Canceling the Self - diagnosis Function

4 . Turn the ignition switch OFF to cancel the self -diagnosis function. After completing repair work, run the self -diagnosis function again to make sure that there are no other malfunctions.

Max Cool Position Function

5 . When the mode control dial is in the MAX A/C position, the heater control panel will automatically select the Recirculation mode and turn the A/C on. The recirculation switch and A/C switch are disabled and cannot be turned off in this mode. If the control panel fails to function as described, replace it.


Dec 5, 2009.
That was a great response and I appreciate it. I ran the diagnostic and no codes surfaced. I'm thinking that perhaps there's a vacuum leak for the control that adjusts the cold air mix through the blower, and that it's stuck shut. The cold air results from a lack of coolant circulating as the temp control also manipulates the heater control valve. It looks like it takes a contortionist to access that area of the system but I'll give it another try.

Eric Powers
Dec 6, 2009.
Your appreciation is received with thanks.

The system does not use any vacumn lines for dontrols. If the heater and AC does not function as desired, the most likely problem would be the air mix motor. They could be intermittently malfunctioning.


1 . Disconnect the 7P connector from the air mix control motor.

NOTE: Incorrectly applying power and ground to the air mix control motor will damage it. Follow the instructions carefully.

2 . Connect battery power to the No. 1 terminal of the air mix control motor, and ground the No. 2 terminal; the air mix control motor should run, and stop at Max Hot. If it doesn't, reverse the connections; the air mix control motor should run, and stop at Max Cool.

3 . If the air mix control motor did not run in step 2, remove it, then check the air mix control linkage and door for smooth movement.

" If the linkage and door move smoothly, replace the air mix control motor.
" If the linkage or door sticks or binds, repair them as needed.
" If the air mix control motor runs smoothly, go to step 4.

Fig. 61: Checking Air Mix Control Linkage & Door

4 . Measure the resistance between the No. 5 and No. 7 terminals. It should be between 4.2 to 7.8 kohm.

5 . Reconnect the air mix control motor 7P connector, then turn the ignition switch ON (II).

6 . Using the backprobe set, measure the voltage between the No. 3 and No. 7 terminals. 6 .

Max Cool-about 1 V
Max Hot- about 4 V

7 . If either the resistance or voltage readings are not as specified, replace the air mix control motor.

To remove the air mix motor, you would have to remove the underdash fuse/relay box.

Dec 7, 2009.