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On-site automotive ac service

Why my car A/C is stuck in heat mode when the cooling mode is on?


A malfunctioning Temperature Blend Door Actuator Motor could be the cause. When the Winter Season begins, and you try to change the A/C settings on the Air Conditioning Climate Control from Cold air to hot air and you cannot control the air temperature.


What is a blend door actuator?



2 Temperature Blend Door Actuator Motor



The blend door actuator is a small electric motor. As you adjust the temperature up and down, the signals go through the actuator to complete the request, positioning the air door on the right position.

When A/C became a popular option on vehicles in the mid to late 1970s, the systems were simple, except for some high levels vehicles, which were often the test bed of things to come.

The control systems were cable actuated, and eventually, vacuum controls were introduced. Most systems were equipped with a heater control water valve, also cable or vacuum controlled.

Automatic temperature control systems had a range of controls: vacuum, electromechanical, and pure electronic devices. They were complicated for the time and often not reliable.


The air delivery system controls the movement of heated and cooled air into and throughout the passenger compartment. The Hvac housing is the plenum unit located and beneath the instrument panel. It contains the evaporator and heater core, and the blower motor assembly and the blower speed control device.

The plenum houses the air doors and door actuators that direct airflow to the correct ductwork. The doors ay be controlled by cables, vacuum, or electrical actuators. Single zone systems are usually equipped with three doors:


The Blend Door Actuator – the blend door determines the temperature of the air flowing through the passenger compartment. If the A/C is operating, the air is dehumidified and cooled. The more air the blend door directs through the heater core, the warmer the air entering the passenger compartment.


Dual zone systems operate in the same manner as single zone systems. However, most dual zone systems use two blend doors: one for the driver side and the other for the passenger side. This design allows for separate temperature settings on each side for the vehicle.



Actuator motors used in automotive Hvac systems can be one of four designs, depending on vehicle manufacturer, system design, year, and model of the vehicle:

  • Tri-state
  • Bi-directional
  • Three wire
  • Two wire

Tri-state Actuator

Temperature Blend Door Actuator Motor

2 Temperature Blend Door Actuator Motor


A tri-state actuator is a five-wire design. Three of the five wires are used for the feedback circuit. The other wires are for ignition voltage and Hvac control head requests.

0 volts will move the motor one way, 5 volts will drive the motor in the other direction, and when the signal wire reads 2.5 volts, the motor stops rotating.

Bi-directional Actuator Motor

Bi-directional actuators use three wires for circuit feedback. The other two wires are the positive and negative circuits that drive the motor. These circuits are controlled by the Hvac control head and move the motor direction based on the selections made at the control head.

Temperature Blend Door Actuator Motor

2 Temperature Blend Door Actuator Motor
Three Wire Actuator Motors

Three wire actuators have a power, ground, and an input wire from the Hvac control head. These actuators use a preprogrammed logic chip containing all the information to drive the motor in the requested direction. When a position change is requested by the vehicle operator, a circuit in the control head sends voltage to the actuator motor. As the motor moves, a potentiometer in the actuator compares the motor voltage to the output voltage from the control head. When both voltage readings are the same, the actuator motor stops. There is no feedback to the control head with this design.

Two Wire Actuator

Two wire blend door actuator motor

3 Temperature Blend Door Actuator Motor


Two Wire actuators create electrical pulses when the commutator rotates across the brushes of the motor. The Hvac control head, which has pre-programmed logic and actuator endpoint references, counts the electrical pulses as the motor moves the door through its sweep from one end to the other end. The actuator endpoints will change as the door seal wears, so if the endpoint counts become too large, a DTC will be set. If the Hvac system loses power, or if a component is replaced, the endpoints must usually be relearned through a calibration process.


How do I know if my blend door actuator is bad?

Binding Actuators

If an actuator binds inside the Hvac plenum, the control module will attempt to overcome the restriction several times before it shuts down the circuit. You will hear the ticking noise. If the binding clears on the next activation, the control module will perform a calibration and set a history DTC.


What does a bad actuator sound like?

If an actuator binds inside the Hvac plenum, the control module will attempt to overcome the restriction several times before it shuts down the circuit. You will hear the ticking noise from the actuator motor.

Where is the heater blend door actuator located?

automotive dashboard

The Blend Actuator Motor is located on the Hvac Box underneath the dashboard. The exact location of the Actuator will depend on the Make, Model and Year of the vehicle serviced.

1 Left temperature actuator screws
2 Temperature blend actuator
3 Left temperature actuator lever
5 Hvac Box

Actuator motor

2015 Cadillac CTS Coupe RWD V8-6.2L SC

How do you test a blend door actuator?

Actuator diagnosis

When diagnosing Hvac actuators, always check the door for binding or restriction, caused by a distorted, worn, or damaged plenum. Check for restrictions that may be caused by a foreign object that is lodged in the door seep, or a broken crank arm on the door assembly.

Do not operate an actuator that is not attached to the door on the plenum. If the door is not attached, the motor can drive past its limits, which usually results in damage to the actuator.

What tools to use for door actuator diagnostics?

Actuator motor operation can be checked with a digital multimeter. Using service information and wiring diagrams for the vehicle, find the correct connector pins for feedback, power, and ground circuits on the actuator. Carefully back probe at the pins, taking care not to pierce the wiring insulation or cause damage to the connector pins. With the meter set on the DC volts scale, move the Hvac selector know and watch for a voltage change as the door position is commanded to change. There should be a voltage change as each position is selected.

  • Digital Multimeter
  • Service Information and Wiring diagrams
  • Scanner

These voltage readings will not give the exact position of the door. However, they will indicate that the door is moving through a complete sweep from one endpoint to the other.

How long does it take to fix a blend door actuator?

The labor time will be different depending on the make, model, and year of the vehicle and if it is a dual zone system or single. The labor will increase because of the time needed to remove all components before we can gain access to the actuator. In some model’s complete removal of the entire dashboard is needed to gain access to the Blend door actuator motor.


2015 Dodge or Ram Truck RAM 1500 Truck 2WD V6-3.0L DSL Turbo

Temperature blend door motor

Left side: 0.5 hours

Right side: 5.2 hours


2013 Ford Focus 2.0L

Temperature blend door motor replacement

Driver side: 0.5 hours

Passenger side: 0.5 hours

ac temperature out of the vents

What temperature should the A/C blow ?

How cold should my AC be at the vent in my car?


The ambient air temperature must be at least 16°C (60°F) .

Do not induce additional air flow across the front of the vehicle during the test.

What temperature should the A/C blow ? 

The A/C system is designed to provide the passenger compartment with low temperature and low humidity air. During periods of high heat and humidity, an A/C system will be more effective in the Recirculation mode (MAX-A/C).

How cold should my AC be at the vent in my car?

A performance test is the best way to determine whether the system is performing up to design standards. This test also provides valuable clues as to the possible cause of trouble with the A/C system.

How do I check the temperature of my car AC?


1-Park the vehicle inside or in the shade.

2-Open the windows in order to ventilate the interior of the vehicle.

3-If the A/C system was operating, allow the A/C system to equalize for about 2 minutes.

Turn OFF the ignition.

4-Install the J-43600 – Acr2000 Air Conditioning Service Center ACR 2000 Air Conditioning Service Center.

5-Record the ambient air temperature and humidity.

6-Record the low and high side STATIC pressure readings.

Are both the low side and high side pressures within the specified value?

More than 16°C (60°F) – 345 kPa (50 psi)

More than 24°C (75°F) – 483 kPa (70 psi)

More than 33°C (90°F) – 690 kPa (100 psi)

How do I check the temperature of my car AC?


Note: Record the relative humidity and the ambient air temperature at the time of the test.

  1. Close the vehicle doors and windows.
  2. Open the driver door window 12.7–15.2 cm (5–6 in).
  3. Select the following HVAC control settings:
    • The A/C is ON.
    • The coldest temperature setting
    • The maximum blower speed
    • Recirculation mode
    • The instrument panel (I/P) outlet mode
    • All I/P outlets are OPEN.
  4. Install thermometers in the left and right center panel air outlets .
  5. Apply the parking brake.
  6. Place the transaxle/transmission in one of the following positions:
    • PARK (Automatic)
    • NEUTRAL (Manual)
  7. Start the engine and warm to operating temperature.
  8. Operate the A/C system for 5 minutes.
  9. Inspect A/C components for the following conditions:
    • Abnormal frost areas
    • Unusual noises
  10. Record the following information:
    • The panel outlet air temperatures
    • The low-side pressure
    • The high-side pressure
  11. Compare the low and high side pressures and the panel output temperatures to the A/C Performance Table below.

Does all the data recorded fall within the specified ranges of the A/C Performance Table below?


A/C Performance Table 2016 Chevrolet Camaro 6.2 L
Ambient Temperature Relative Humidity Low Side Service Port Pressure High Side Service Port Pressure Maximum Left Center Discharge Air Temperature
13–18°C (55–64°F) 0–100% 186–289 kPa (27–42 psi) 930–1260 kPa (135–183 psi) 10°C (50°F)
19–24°C (66–75°F) Less than 40% 186–289 kPa (27–42 psi) 909–1212 kPa (132–176 psi) 9°C (48°F)
Greater than 40% 213–323 kPa (31–47 psi) 1019–1329 kPa (148–193 psi) 13°C (55°F)
25–29°C (77–84°F) Less than 35% 220–310 kPa (32–45 psi) 1061–1288 kPa (154–187 psi) 12°C (54°F)
35–50% 241–323 kPa (35–47 psi) 1123–1322 kPa (163–192 psi) 13°C (55°F)
Greater than 50% 254–351 kPa (37–51 psi) 1157–1391 kPa (168–202 psi) 15°C (59°F)
30–35°C (86–95°F) Less than 30% 248–337 kPa (36–49 psi) 1157–1391 kPa (168–202 psi) 14°C (57°F)
30–50% 261–358 kPa (38–52 psi) 1198–1419 kPa (174–206 psi) 15°C (59°F)
Greater than 50% 282–378 kPa (41–55 psi) 1240-1460 kPa (180–212 psi) 18°C (64°F)
36–41°C (97–106°F) Less than 20% 282–365 kPa (41–53 psi) 1288–1508 kPa (187–219 psi) 17°C (63°F)
20–40% 289–378 kPa (42–55 psi) 1302–1522 kPa (189–221 psi) 18°C (64°F)
Greater than 40% 303–392 kPa (44–57 psi) 1329–1529 kPa (193–222 psi) 19°C (66°F)
42–46°C (108–115°F) Less than 20% 316–392 kPa (46–57 psi) 1419–1612 kPa (206–234 psi) 18°C (64°F)
Greater than 20% 323–406 kPa (47–59 psi) 1433–1612 kPa (208–234 psi) 20°C (68°F)
47–49°C (117–120°F) Below 30% 351–427 kPa (51–62 psi) 1529–1701 kPa (222–247 psi) 22°C (72°F)


School bus ac repair

Bus Air Conditioning service & repair.


We provide on-site A/C services for school buses in Miami-Dade County.We help you get your school bus ready for the reopening of the schools.

In-cabin air filter maintenance /replacement

Carrier Units service & repair

Thermo King Units service & repair

New hoses installation

Leaks repair

Air conditioning compressor replacement

Condenser coil replacement

Evaporator coil replacement

Give us a call for a fast & reliable service by one of our ASE certified technicians.

How can i make my car ac colder

How can i make my car ac colder

Radiator cooling fan should be working at 100 %


Two fan system

One fan system







The radiator fan(s) should be on any time the A/C is on.



Road debris affect the heat transfer of heat exchangers in your vehicle and the overall capacity of the air conditioning.

Clean all the road debris outside the car

(on the windshield)

(on the condenser coil)

Clean all the debris inside the car

In cabin air conditioning filter

Evaporator core

Screen air inlet



-Check Drive Belt tension

An excessively loose drive belt will negatively impact the air conditioning compressor capacity.



Check refrigerant charge with gauges (You need special hvac equipment and EPA certifications)

Check refrigerant charge by sensing A/C lines temperature (Do it yourself)


-Open the hood to get access to the engine compartment (Be aware of all moving parts and hot components)

-Start the engine up.

-Set the A/C Climate control for Maximum blower speed position.

-Set the A/C Climate control for Maximum cold temperature position.

-Let the A/C system run for 5 -10 minutes.

-On the engine compartment identify the A/C lines.

-The Liquid line should be warm to cool even in a hot day

. (A liquid line cold or hot indicates a problem)

-The Suction Line should be cold

. Heavy frost or excessive moisture condensation on the Suction Line indicates a problem.

. Ambient temperature or too hot Suction Line indicates a problem.

-There should be a Temperature difference (TD) between the Liquid Line and the Suction Line (Check temperature before the Metering Device)

If the temperature of both lines is the same, it indicates a problem in the A/C system:

1-Compressor not pumping.

2-Compressor not turning on.

3-Low on refrigerant.





A/C compressor

A/C operation, normal noises.

Normal noises include the sounds of A/C compressor clutch engagement, the blower motor, moving blend air and mode doors, and pressure equalization after vehicle is shut down.

Noises that could indicate the need for a/c compressor service or replacement include:

  1. Growling noise with compressor disengaged
  2. Whistling noise
  3. Grinding noise
  4. Squealing noise
  5. Rattling noise
  6. Growling noise with compressor engaged
  7. Banging noise
  8. Knocking noise

Why is my AC making a weird noise?

Banging noise: If liquid refrigerant enters the compressor, a thumping, banging noise will result.

Knocking noise: Heavy knocking compressor noises come from refrigerant system blockage, incorrect pressures, or internal damage.

Growling noise with compressor disengaged: A worn compressor pulley bearing or clutch bearing will cause a growling noise.

Growling noise with the compressor engaged: A/C compressor internal bearings damage.

Squealing noise: A loose, dry, or worn A/C compressor belt will cause squealing noise. This noise will be worse during acceleration.

Worn or dry blower motor bearings may cause a squealing noise when the blower motor is running

Rattling noise: A loose or worn clutch hub or loose compressor mountings bolt will also cause rattling noise from the compressor.

Knocking noises: This type of noise from the compressor usually indicates internal damage, especially on piston-type compressors. Always check the compressor mounting and brackets before condemning the compressor for noise.

A loose mounting can cause knocking noises from the compressor area that may be mistaken for internal compressor noise.

Grinding noise: When car accessories pulley bearings are failing, they can make this kind of noise.

Diagnosing a bad or failing Ambient Temperature Sensor.

  1. The air conditioning AUTO MODE wont work
  2. Inconsistent cooling or not cooling at all.
  3. A/C compressor inoperative
  4. Incorrect reading on temperature gauge. Usually a default negative temperature.


The most common variable resistor is a thermistor.Thermistors change resistance based on temperature changes. There are two different styles of thermistor: NTC (Negative Temperature Coefficient) and PTC (Positive Temperature Coefficient).The difference is in how they react to temperature changes.

As temperature rise:

-PTC thermistor-resistance increases

-NTC Thermistor-resistance decreases

The NTC thermistor is more common than the PTC thermistor.

Here are some examples of thermistor in automotive circuits:

  • Engine temperature sensor
  • Evaporator temperature sensor
  • Ambient temperature sensors-In-car and outside sensors
  • A/C High Side Refrigerant Temperature Sensors
  • A/C Low Side Refrigerant Temperature Sensors
  • Sun Load Sensors (Not all sun load sensors are thermistor some are photoresistors.A photoresistor measures the amount of light hitting it .As the light intensity increases , sensor resistance decreases. Thats the why a photo resistor works so well as a sun load sensor. Some manufacturers use a photodiode. A photodiode works in a manner similar to the photoresistor.
What does the ambient temperature sensor do?

It prevents the compressor from engaging when ambient temperatures get too low. The oil that resides inside of a compressor can get very cold during the winter months. If the compressors clutch is energized while the oil is cold and thick, improper compressor-lubrication would result.

Where the ambient temperature sensor is usually mounted?


Mounted to the radiator support, in front of the condenser where it can sense outside temperatures without being affected by engine heat.

How does ambient temp sensor work?

A lot of air conditioning systems are supposed to run when you turn the defroster on, to help remove moisture from the air. But when outside temperatures are very low refrigerant oils wont flow and lubricate the system properly.

The ambient temperature sensor prevents the compressor from running when its too cold for the system to work safely. These switches open when the temperature drops below a preset temperature,usually below 32 F

A/C system check up in Miami-Dade County

How do you diagnose an air conditioner

Air Flow

Car ac blower motor replacement service & cost
No air flow

  1. Inspect blower motor
  2. Inspect blower motor resistor
  3. Inspect fuse
  4. Inspect A/C climate control
  5. Inspect connectors
  6. Inspect harness
  7. Inspect hvac box for


No cooling

Automotive ac system.Head control set.Hvac electrical and electronic

  1. Inspect A/C switch
  2. Check refrigerant level
  3. Inspect clutch relay
  4. Inspect PCM/BCM/ECM
  5. Inspect A/C pressure switch
  6. Inspect compressor clutch coil
  7. Inspect compressor clutch
  8. Inspect compressor clutch air gap
  9. Inspect condenser
  10. Inspect condenser fan
  11. Inspect radiator fan
  12. Inspect evaporator temperature control devices
  13. Inspect temperature sensors control devices
  14. Inspect climate control
  15. Inspect in cabin temperature sensors
  16. Inspect sun load sensors
  17. Inspect power steering pressure sensor

Bad Smell

Leaking evaporator core on site replacement.
2000 Toyota 4runner sr5 on site evaporator replacement.

  1. Check cabin air filter
  2. Check evaporator core
  3. Check hvac box drain tube
  4. Check re-circulation air door /actuator
  5. Check hvac box seals


Clicking noiseA/C compressor relay

  1. Check A/C clutch
  2. Inspect A/C clutch relay
  3. Inspect cycling switch
  4. Inspect refrigerant level
  5. Inspect evaporator temperature sensor

Worn serpentine belts & car ac compressor output.
Serpentine belt type of damage and the negative impact they have on the air conditioning system.

  1. Check drive belt
  2. Check belt tensioner
  3. Check compressor for seizing

A/C compressor

  1. Check compressor
  2. Check compressor clutch
Other helpful tips

Replace the receiver driver with every A/C service.
Replace cabin air filter annually
Ensure that service valve caps are in place at every A/C service.

Does engine coolant affect ac performance?

High coolant temperature affects A/C performance.

The engine cooling system has an indirect influence on the performance of the A/C system. High under hood temperatures can be the cause of poor A/C output. 

Always verify correct operation of:

  • Engine coolant level and condition
  • Low coolant will cause high under hood temperatures
  • Does the cooling system need flushing?
  • Has the vehicle followed the manufacturers service intervals for flushing?
  • Does it have the correct coolant in it?

  • Thermostat
  • Has the thermostat ever been replaced?
  • Is it stuck, not closing or opening all the way?

  • Radiator
  • Is the radiator plugged internally or externally?
  • Are there any signs of leaks?

  • Water pump
  • Is the mechanical pump circulating the coolant properly?
  • Are electric pumps working properly?
  • Should it be replaced when servicing the timing belt?
  • Belts,tensioners,and pulleys
  • Check for proper belt tension and verify the belt is not slipping
  • Check tensioner alignment

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