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…
The three most common causes of clicking noise from the dashboard are:
In this post, you’ll learn about the most common causes of dash-clicking noise and how to diagnose and fix them.
Before we get into the top 3 common causes of dashboard clicking, I’ll point out a couple of common sources of car clicking sounds. The sounds may not originate from the dashboard area but can sometimes sound like they are. Anyhow here they are:
- A clicking noise while you are attempting to start your car is a sign of a flat battery. If you think that sounds like a fair description of your problem, then go ahead and check out this post, “Car won’t start clicking sound.”
- Dash lights flashing together with a clicking sound with the engine is off; if that sounds familiar, then check out this post, “Dash lights flashing when car off.”
If neither of these sounds right, not to worry; we’ll cover dashboard clicking proper next.
1 Heater Motor Calibration
Your car’s heater, known as an 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 its job correctly, it must receive accurate blend door position readings.
Sometimes the positions are miscalculated, which causes erratic motor activation. Recalibrating the system fixes the problem.
An 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 dashboard 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 the exact position of the blend doors, known as counts.
- Control module – The module receives inputs from stepper motors and temp sensors and outputs commands to the stepper motors, fan, heater valve, and a/c system.
The heater control module tracks your blend door positions; it needs this information to direct the air as per the operator’s 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
A flat battery is a very common cause of HVAC calibration issues and a ton of other system calibration issues too.
I wrote a post about all the issues a flat battery or disconnecting a battery can cause, and this post also shares a top tip for side-stepping calibration issues. “Car won’t idle after flat battery.”
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. Some vehicles will require a bidirectional scan tool to calibrate the HVAC system. You can check out the one I recommend here on the Auto electrical repair tools page.
Here’s a relearn or also known as a recalibration procedure for some GM vehicles:
- Turn ignition on.
- Turn Auto button.
- Turn ignition off.
- Remove the 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, the system is now calibrated.
Recalibration 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 car’s heater system uses several stepper motors attached to blend doors and is most likely the source of your dashboard clicking 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 anymore (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 there it was. A pen was 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, a 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 motor by hand works, replace the stepper motor.
You’ll find many of the tools I use here on the “Mechanics tools page”.
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.
Remove the pigtail connector, and two small 6, 7, or 8mm bolts (the usual fasteners), a 1/4 ratchet, and a socket work great as the 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. Check out the scan tool I use here on the Mechanics tools page.
3 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 three or more separate fuse boxes, 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 two fuse box’s behind the dash, all bristling with relays.
What’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, horns, wipers, starter motor, power seats, etc.
Sending power through the control side of the relay magnetizes it and causes copper armature contact points to close, completing the load side circuit and powering up the consumer.
The relays emit an audible click as the contact points close and open; this is a 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 it with one of its neighbors; you’ll often find many identical relays in the same fuse box. Swapping the relay is a fast and simple way to diagnose. Shaking a faulty relay will often produce a rattling sound.
Hotwire the relay and check resistance using a voltmeter or check out this simple plug-and-play relay tester here on the Auto electrical repair tools page.
How To Replace A Relay
Replacing is easy; pull out the old and make sure the pins are correctly aligned before pushing home the new relay.
Having a workshop manual for your vehicle is always a good plan; they only cost a few dollars but will save you a packet. Good manuals cover repair diagrams, wiring diagrams, system operation overview, troubleshooting sections, fastener torque specs, sequences, etc., all mission-critical info.
I wrote a ton of posts about all the most common auto electrical problems and repairs, they are all written with the beginner in mind, and you can check them out right here in the auto electrical blog section.
About the Author
John Cunningham is a Red Seal Qualified automotive motive technician with over twenty-five years of experience in the field. When he’s not writing about car repair, you’ll find him in his happy place – restoring classic cars.
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John Cunningham is an Automotive Technician and writer on Rustyautos.com. He’s been a mechanic for over twenty-five years and has worked for GM, Volvo, Volkswagen, Land Rover, and Jaguar dealerships.
John uses his know-how and experience to write fluff-free articles that help fellow gearheads with all aspects of vehicle ownership, including maintenance, repair, and troubleshooting.