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Jim, ASE Certified Technician
Category: Chrysler
Satisfied Customers: 1317
Experience:  ASE Certified A6,A8,L1 and California Licensed Smog Technician
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1994 chrysler concord: reaches normal operating temperature..heater

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my 1994 chrysler concord with a 3.3 engine reaches normal operating temperature but no heat comes out of heater. Temperature control calling for max heat. What could be wrong here. New thermostat, coolant system flush including the heater core and still no heat from heater

Jim :

The blend door accuator might be stuck in the cold position, you will want to do the following test.

Jim :
Connect a voltmeter to the Red/White wire at the actuator on the bottom of the HVAC housing.

With the key off, remove the IOD fuse, it is fuse 19 in the inside fuse box. It can be identified by the fact that it sticks out farther than the others in the bottom row.

Reinstall the fuse and start the vehicle, monitoring the voltage on the Red/White wire. It should cycle from below 1 volt to over 4 volts.

If it doesn't turn the key off, remove the fuse again. Connect the voltmeter between the Dark Blue/Red wire and the Brown/White wire. Reinstall the fuse and start the vehicle. The voltage should cycle from + 8-10 volts to - 8-10 volts.

If this works but there was no change on the Red/White wire, replace the actuator.
Customer: replied 6 years ago.

Jim, I can hear the blower air changing sounds when I move the heater temp from cold to hot so I think the blend door actuator is working. Is there a control valve controlling the coolant flow through the heater core? Ken


Try the following test.


The Automatic Temperature Control (ATC) system can be diagnosed two ways. The scan tool (DRB) can be used, or the vehicle's own control head display may be used.

The control head can only be placed into the diagnostic mode while the engine is running and the vehicle is not moving. Set the control to a 75°F. setting (so there is no confusion with 23-36 Diagnostic Trouble Codes).


To place the system into it's diagnostic mode, press and hold the floor, mix and defrost buttons (at the same time). The ATC head display will begin to blink. When the control head display begins to blink release the floor, mix and defrost buttons. Once the control head enters diagnostic mode, the display on the control head will continue to blink. This occurs until it completes its tests and calibrations. Then it will display any diagnostic trouble codes that are present in the Body Control Module (BCM) . If there are no diagnostic trouble codes the system will return to its normal operation as indicated by temperature display.



Diagnostic trouble codes related to the ATC system will appear on the display in numerical form. The diagnostic trouble codes are stored in the BCM and diagnostic trouble code numbers can range between 23 and 36. The control head can only show one diagnostic trouble code at a time. Under certain circumstances more than one diagnostic trouble code could be in the memory To scroll through any additional diagnostic trouble codes, press the panel button.

Customer: replied 6 years ago.
You never answered the question if there was a variable control valve which controls how much fluid flows through the heater core. Are you saying that the coolant flows through the heater core full throttle as soon as the water pump turns and the air temp from the heater is dependant on doors to the fresh air supply? Ken
This vehicle doesn't show a heater control valve. Run the test and see if you have any codes and let me know.
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