Diagnose and fix Ford Heater
Here are some tips on fixing a Ford heater problem. The known problems range from no heat to heat on one side, low heat and all variations between.
Where to start diagnosis with Ford heater issues
Always start by checking engine coolant level. Low coolant will result in low heat or no heat. If low, add coolant. Next, check the hoses to the heater core when the engine is hot. Both the incoming and outgoing hoses should be HOT. If one hose is hot and the other cold, you’ve got a clogged heater core, a restriction in the system or air in the system. If both hoses are hot, chances are high you’ve got a BLEND DOOR or BLEND DOOR ACTUATOR ISSUE
Diagnose and fix a blend door actuator
The blend door actuator in a late model Ford Heater is an electric motor with position feedback. It opens and closes the blend door to provide the requested air temperature. The blend door actuator is controlled by the HVAC controller. The controller provides + and – voltage to the blend door motor and reverses the voltage to move the motor in the opposite direction. The controller also supplies a 5-volt reference signal to the blend door actuator variable resistor. As the motor moves, the variable resistor provides a varying voltage reading indicating position.
During a calibration cycle the HVAC controller commands the actuators to open and close until they reach internal stops built into the HVAC case. Once calibrated, the controller knows the variable voltage readings for full open and full close.
Ford heater blend door actuator trouble codes
Before you start replacing parts, you should know that the controller actually stores trouble codes to point you in the right direction. The two most common blend door actuator trouble codes are:
B2266 (Left Side Blend Door Circuit Failure—the controller has provided voltage to the driver’s side actuator but doesn’t see a change in feedback voltage from the variable resistor.
B2267 (Right Side Blend Door Circuit Failure— the controller has provided voltage to the passenger side actuator but doesn’t see a change in feedback voltage from the variable resistor.
How to test Ford heater blend door actuator
The Ford shop manual shows several ways to test the blend door actuator.
Test resistance on the variable resistor at the actuator
Jumper the motor connections at the actuator with fused battery voltage to move the motor.
Test for + and – on each actuator connector coming from the HVAC controller. If you see those voltages when commanding a temperature change that confirms the controller is working properly.
Refer to the shop manual for the different resistance values.
Test the blend door actuator
The Ford Heater temperature control issue comes down to this:
It’s either an HVAC controller issue or,
A problem with the variable resistor inside the blend door actuator, in which case you must replace the actuator or,
A problem with the blend door actuator motor, in which case you must replace the actuator or,
A problem with a binding or stuck blend door.
Best advice for diagnosing and fixing a Ford heater blend door actuator problem
Remove the blend door actuator and try opening and closing
the blend door by hand. If it moves freely, you’ve eliminated the blend door itself as the cause. Using a fused jumper wire, provide power and ground to the actuator using the wiring diagram to see if the motor operates. If the motor doesn’t move, replace the actuator. In most cases, it’s the actuator that’s bad. However, you are risking the cost of the actuator if the problem turns out to be in the HVAC controller. Get a shop manual and test the resistance values and + and – voltages in the wiring harness coming from the HVAC controller.
©, 2017 Rick Muscoplat
You can perform these tests by following the Ford Heater wiring diagram below.
Posted on by Rick Muscoplat
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