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Ticking Sound From A/c System

jbeall

By jbeall
in Ask A GM Technician

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jbeall Enthusiast

jbeall

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Hi All,

 

Recently we had some work done at a dealership to address this ticking sounds we've been hearing—they found a code in the HVAC system of the vehicle, B3770. Found bulletin on this code—ticket stated 'tightened pins in connector per bulletin and cleared codes, recalibrated, and tested ok.'

 

However, after a few hours the sound returned (not as loud as before), and within a few days, it was back to the same ticking sound as before.

 

They thought it was a actuator that was acting improperly, and they replaced the actuator in question. The ticket for this repair states is was the "RH AIR TEMP ACTUATOR."

 

But, still no success. It went away for a few hours and then was back.

 

 

 

Here are the steps to reproduce:

 

 

  1. We have only heard the ticking sound when it's hot outside the vehicle (80+), so wait until it's at least 80 degrees.
  2. Turn the vehicle on, and press the “Auto” button of the A/C controls. This will make sure that the A/C is on, and it is in “Auto”.
  3. The fan should come on, and turn up to high. After several minutes, the vehicle cabin should have cooled down, and the fan will turn down to a lower speed setting. It is in this speed setting that we hear the ticking.
  4. The ticking will stop if you press the vent control button, which is the button immediately below the “Auto” button. You need to press it firmly and it will change from delivering the air only out of the dashboard vents, and deliver air out of both the dashboard and the foot vents. When this change happens, the ticking stops.

They think that perhaps more than one actuator is ticking, and so they are going to try replacing another actuator--the one they have in mind is above and to the right of the gas pedal.

 

Are they on the right track? Do you have suggestions on what else we should be checking?

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