Do you have annoying clicking (similar to seeking CD player) sound coming from inside of your Toyota dash, sometimes only happening at set heater temperature setting? It could be “indecisive” heater control servo.
Below is how I fixed the noise in a Toyota Ist (hint: it is was a problem with sliding contacts inside of the servo).
To get to the servo (it sits on top of the heater/AC ducting) you need to remove head unit and heater controls. To get to screws in Ist you need to unclip silver trims (not visible):
The heater control and head unit surround/centre vents is held by couple of screws. After removal of the screws the surround just unclips:
The heater control is connected via one plug and a corrugated hose (which vents to a thermistor in the heater control unit):
The servo is located in depth of the dash board:
The servo is held by 3 screws (it has 4 holes, just to confuse people) and is connected via single plug
It was very hard to unlatch the levers so I removed it with them in place. The was 1 screw and a plastic washer holding the levers in place:
Servo is held together by plastic clips around the perimeter:
The problem is due to wear contact springs lose tension:
Here are the contacts in greater detail:
The fix is to bend contacts up and clean the contact surface from carbon (while trying not to remove too much grease).
To reinstall the servo make sure that the levers sit correctly. Check that the flaps are actuated properly by moving the lever by hand:
After reassembly check maximum temperature (should be 50-60 degrees Celsius):
Check minimum temperature (should be around 8 degrees Celcius, providing that the A/C is working):
Check set temperature on lower end (in this case 22 degrees Celsius):
Check set temperature on higher end (27 degrees Celsius):
Note: temperature settings take a while to stabilize.
Success! No more noises!