Squeaks and rattles inside a car drive me wild, I’ve got to find them. On a trip down the country last year my car developed a clicking noise behind the dashboard…. 50 miles later I was pulling the dashboard out with my bare hands. This is what I found…
Why is my dashboard clicking? The three most common causes of a clicking noise from the dashboard is:
- Heater control module lost calibration
- Faulty blend door stepper motor
In this post you’ll learn about the most common causes of a dash clicking noise, how to diagnose them and how to fix them.
1 Heater Motor Calibration
Your cars heater known as a HVAC (Heating Ventilation Air Conditioning) system is a clever piece of kit. It is way more sophisticated than it looks. The system uses sensors, blend doors and motors to control heating/cooling and airflow. Keeping track of all the motor positions, temperatures, fan speed and dual zone requests is a job only a computer could handle.
The HVAC control module manages it all but in order for it to do it’s job correctly it must receive accurate blend door position readings. Sometimes the positions are miscalculated which causes erratic motor activation. Re-calibrating the system fixes the problem.
A HVAC system consists of various components:
- Heater Matrix – Matrix is the housing that contains all the components of the HVAC system. It’s a large bulky unit that takes up much of the space behind the dashboard.
- Heater core – Resembles a small radiator, located behind the dashboard, hot engine coolant is routed through it.
- Fan – Located behind the dash board and employed to blow air over the heater core where the air is warmed before entering the cabin.
- Temperature sensors – Sensors feed live readings to the control module.
- Blend doors – Doors positioned inside the matrix that open and close to direct air through different zones such as windshield, floor, face etc.
- Stepper motors – Are motors connected to the blend doors that move in very precise increments when commanded. They signal the heater control module with their exact position of the blend doors, known as counts.
- Control module – The module receives inputs from stepper motors and temp sensors and out puts commands to the stepper motors, fan, heater valve, a/c system.
Your blend door positions are tracked by the heater control module, it needs this information to direct air as per the operators requests. As you know when the blend door positions are lost the controller malfunctions.
Common reasons blend door locations are lost include:
- Flat car battery
- Disconnected battery
- Faulty Stepper motor
- Stuck blend door
- Stepper motor removed or disturbed without re-calibrating
How To Calibrate The Heater
Calibrating the HVAC system isn’t difficult but does typically require several time sensitive steps. All manufacturers will have their own sequence, here’s a the relearn also known as a re-calibration procedure for some GM vehicles:
- Turn ignition on.
- Turn Auto button.
- Turn ignition off.
- Remove fuse from the HVAC for 1 minute.
- Turn ignition on – the HVAC system is now in the relearn mode and automatically runs through all the blend door positions. Do not touch the controls for 2 minutes.
- Turn the ignition for 15 seconds only.
- Start the engine, system is now calibrated.
Re-calibration fixes a lot of HVAC issues, if however the problem reoccurs a failing stepper motor is the most likely root cause.
2 Faulty Stepper Motor
A faulty or stuck stepper motor is a likely cause of your clicking sound. I had this exact problem and I’ll share how I fixed it for free in less than ten minutes. What’s a stepper motor? A stepper motor is an electric motor employed to move in very precise increments. Several stepper motors are used in automotive systems.
Your cars heater known as a HVAC (Heating Ventilation Air Conditioning) system uses several and is likely to be the source of your noise.
How To Diagnose Faulty Stepper Motor
As your heater is controlled by a control module (computer) a scan tool is the best place to start. A unique fault code will likely be recorded and you’ll find that code will identify the faulty stepper motor type and location. I understand most won’t have a scan tool, so we’ll attack this problem old school.
We’ll use our ears. When my dashboard started to click I changed the heater settings and noticed the clicking noise change slightly and so I deduced it must be a stuck door or stepper motor. When I couldn’t take the noise any more (50 miles, I’m stubborn), I stopped at a gas station to investigate.
I simply followed the noise, it was loudest behind the passenger side dash so I removed the glove box and their it was. A pen stuck in the blend door.
Remove the pen, problem solved. But the pen had one final sting, I later found it leaked ink all over the door pocket.
You may find an obstruction, a stuck door, disconnected actuator or A faulty motor, all are common.
Moving the blend door controls will activate the stepper motors. Pay attention to the gears and pivots, check they’re not worn.
As your stepper motor is clicking, we can assume the circuit is OK, but the motor itself could be faulty. Try helping the motor by opening the blend door as you operate the control panel.
Some lube may help, try a little WD40 on the gears and pivots. If you find helping the the motor by hand works, replace the stepper motor.
How To Replace The Stepper Motor
Access can be a total pain in the ass, I got lucky with my fault but don’t be surprised to spend some time on your back laying upside down.
Remover the pigtail connector and two small 6, 7 or 8mm bolts (the usual fasteners) a 1/4 ratchet and socket works great as space is tight.
Replacing is the reverse but the system will need to be calibrated. The control module has lost the counts and needs to relearn them.
2 Faulty Relay
Your vehicle is packed with electronic kit and they require a ton of circuits, control modules and relays. There’s so much electronic kit in vehicles today, your vehicle may have 3 or more separate fuse box’s all containing fuses and relays.
It’s not unusual to have a fuse box under the hood and under the dash and another in the trunk. Some vehicles run 2 fuse box’s behind the dash all bristling with relays.
Whats’s a relay? A relay is a small electro-mechanical device that’s employed to control a heavy amped circuit (Load) using a low amp circuit (control). It’s used in lots of circuits, – lights, horn, wipers, starter motor, power seats etc.
Sending power through the control side of the relay magnetizes it and causes a copper armature contact points to close completing the load side circuit and powering up the consumer. The relays emits an audible click as the contact points close and open, this is normal operation.
A faulty relay or dirty contact points may cause the relay to engage and disengage quickly causing a repeating clicking sound.
How To Diagnose A Faulty Relay
Use your ears to locate the offending relay, place your hand on the relay and feel it click. Remove the relay and swap with one of it’s neighbors, you’ll often find many identical relays in the same fuse box. Swapping the relays is a fast and simple way to diagnose. Shaking a faulty relay will often produce a rattle sound. Hot wire the relay and check resistance using a volt meter.
How To Replace A Relay
Replacing is easy, pull out the old make sure the pins are correctly aligned before pushing home the new relay.
AC stopped blowing cold air? Common AC problems include:
- Low refrigerant
- Refrigerant leak
- AC compressor clutch fault
- Drive belt fault
- Fan fault
- Coolant system fault
- Engine fault
- Transmission Fault
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