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Dodge Repair/2000 dodge caravan heater problem

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QUESTION: heat doesnt work....blower motor works.....but only blows cold air...changed the thermostat, heater core and fuses all good....ran all the air out of the system....running at normal operating temp....controls for  vents seem to work, changes from floor to bilevel to defrost.....i suspect maybe something with the hot/cold selector but have no idea how to go about it"

ANSWER: Hi Rob,
I have the '98 and the '02 manuals which differ in their descriptions of the HVAC control unit and its calibrations and diagnosis. If you could describe the appearance of the control panel of your unit it would help me to know which applies to your '00.
In any case there is a procedure to go through which will self-calibrate the blend door, which is the device which sends air variably across the heater coils or the ac coils depending upon what temp is requeested. That procedure depends upon which year service manual applies to your '00.
So let us start by describing the control unit to me and we'll go from there.
Roland

---------- FOLLOW-UP ----------

QUESTION: blower motor knob all the way to the right with the vent selector knoknob just to the left of it....just to the left of the knobs is the blend lever going across the top which moves from left to right and below the  is a row of buttons that turn on the ac.and higher blower motor setting and the rear defrost....then finally allthe way to the left of thecontrol panel is a vertical row of buttons that control the rear wiper and window wash....i believe it would be the 98 manual as i had a 98 and the controls looked exactly the same

ANSWER: Hi Rob,
Thanks for the description and you are correct that is like the '98,
The engine must be running to do the calibration/cooldown tests.
I would try initiating the self-diagnostic/calibration procedure to see if you can get the unit to go through that process as described in the following procedure which is taken from the shop manual:

DIAGNOSTICS
During the Actuator calibration, diagnostics are performed on the actuators and evaporator temperature Fin Sensor. Once diagnostics are completed the REAR WIPER and INTERMITTENT LED's will flash to indicate either a successful calibration or the appropriate fail code(s) At this time manual testing of the Blend, Mode and Driver (if equipped) potentiometers can be performed. If a failure is detected during Diagnostics a fault will be set in the control. When Ignition is cycled OFF and then ON or Diagnostics is aborted, the REAR WIPER and INTERMITTENT LED's will flash simultaneously showing that a failure has occurred. The control will not indicate the fail code, but only that a failure had occurred during the last diagnostics test. The only way to clear the failure codes is repeat the Calibration Diagnostic and Cooldown test, after all repairs are completed.

COOLDOWN TEST
This test has been designed for performance testing of the A/C system at the manufacturing facility. If the HVAC control module is replaced, the Cooldown test will occur during Calibration test. Cooldown will not occur on Heater Only units. During the Cooldown test the control will monitor the temperature of the Fin Sensor. The A/C system must be able to bring the evaporator temperature down a predetermined minimum amount in less than 2 minutes.

CALIBRATION/COOLDOWN LED DISPLAY CODES
See table for definition of flashing LED's. If no problems are found, the control functions normally.

CALIBRATION/COOLDOWN LED DISPLAY CODES
LED'S PASS/FAIL CORRECTIVE ACTION
NO LED'S FLASHING-NORMAL OPERATION PASSED CALIBRATION, DIAGNOSTICS AND COOLDOWN NONE
REAR WIPER AND INTERMITTENT LED'S FLASH SIMULTANEOUSLY FAILED CALIBRATION DIAGNOSTICS RUN CALIBRATION TEST
A/C AND RECIRC LED'S FLASH SIMULTANEOUSLY FAILED COOLDOWN  RUN COOLDOWN TEST
REAR WIPER AND INTERMITTENT LED'S ARE FLASHING SIMULTANEOUSLY A/C AND RECIRC LED'S ARE FLASHING SIMULTANEOUSLY FAILED CALIBRATION, DIAGNOSTICS AND FAILED COOLDOWN TEST  RUN CALIBRATION TEST

CALIBRATION/DIAGNOSTICS TEST ENTRY
TO INITIATE TESTS:
Set Blower motor ON HIGH
Set Mode position to Panel
Open all A/C outlets
Set Temperature to Cold (Both slide pots if equipped)
Depress WASH and REAR WIPER button simultaneously for 5 Seconds (Until all LED's light)
RESULTS:
All LED's will turn on for 5 Seconds
Calibration Test is running when REAR WIPER and INTERMITTENT are alternately flashing. Cooldown test is running if A/C and RECIRC are alternately flashing.
Acceptable results is REAR WIPER LED is the only LED flashing. Push Rear Wiper to exit.
After all tests have passed, Calibration Diagnostics and Cooldown can be run separately.
COOLDOWN TEST ENTRY
TO INITIATE TESTS:
Set Blower motor ON HIGH
Set Mode position to Panel
Open all A/C outlets
Set Temperature to Cold (Both slide pots if equipped)
Depress WASH and A/C simultaneously for 5 Seconds
NOTE: Prior to start of test, If the evaporator is already cold, the system will fail test. To correct, operate system with A/C OFF and the blower motor ON high for three minutes prior to starting test.

RESULTS:
All LED's will turn on for 5 Seconds
Cooldown Test is running when A/C and RECIRC. are alternately flashing. If A/C and RECIRC. are flashing simultaneously, Cooldown has failed.
CALIBRATION DIAGNOSTICS AND COOLDOWN ABORT
Test can be aborted by doing one of the following:

Depressing Rear Window Defogger, RECIRC and Rear Wiper buttons.
Cycling Ignition OFF and then ON.
Control will automatically abort after 15 minutes from the time Calibration Diagnostics and Cooldown was entered.
The HVAC control module will return to normal operation or may indicate unsuccessful Calibration Diagnostics or Cooldown test by LED's flashing simultaneously
Give it a try and let me know what happens with the lights. There are about 4 pages of analysis of the results which I can xerox copy and postal mail to you if needed.
Please 'rate' my answer (see below).
Thanks,
Roland



---------- FOLLOW-UP ----------

QUESTION: ok i did the calibration test....and it goes thru all the modes .....seems to switch thru the vents letting the air flow thru them all and it did....and to my surprise the first thing the it must test is the air blend door cause for the first 5 seconds of the test hot air came out  .....but when the test was over back to not having heat...almost leads me to believe the air blender slider on the controls is broken and it broke while it was on cold thus not letting me switch it to the heat....what are ur thoughts

Answer
Hi Rob,
After completion of the tests what were the LED's doing or were they all off?
The lever on the slider is basically a variable resistor so you could remove the control panel and see whether it is making electrical contact using an ohmmeter. One end of the resistor is grounded and the 'sweeper' attaches to an internal circuit board connection which you should be able to identify visually. Measure the resistance between the slider and the ground (any shiney metal surface of the body or pin 21 of the HVAC control blue plug). If it is not making a variable resistance as you move the leaver then try a spray can of electrical contact cleaner inside the lever/slider module.
Please rate my answer.
Roland

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Roland Finston

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Get a Free Fast answer to your repair question about a Chrysler/Dodge/Plymouth car, minivan, SUV, or truck. Problems with electronically controlled engines and transmissions as well as body wiring problems are my specialty. This free troubleshoot advice forum helps you diagnose faults, minimize repair costs or do-it-yourself.

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Five decades as a 'do-it-yourselfer' on domestic and imported cars

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Degrees in Physics/bruised knuckles.

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