Clicking Noise From Heater

[Warstud]

I"m getting a clicking noise when I shut the heater off or turn the defrost on. It doesn't click when the heater is in other positions though. It's a 2007 Trailblazer.

 

[expat]

A dried leaf in the fan blades?

 

[Chris142]

Blend door motor

 

[The_German]

Try and dig up the wiring diagrams of any system that is causing the clicking maybe you have a short on the return path to ground somewhere (check each G location and clean as necessary) and check any relay.

Activate the relay (wiring diagram for the coil and contact is on the relay itself) and check the ohms and look up the spec I think the coil may not have enough windings left to hold the gate if you aren't seeing at least 70-80 ohms coil and almost no resistance on the contact side that feeds the load.

Anyway clicking may be a bad relay especially if we are talking about the rear def circuit I don't remember if that is a relay or a maxi fuse. I'd guess relay as the rear def must pull a few amps as a consumer.

If the wiring diagram doesn't have any relays I'll have to think about it more.

 

[cb_13]

Probably a door actuator motor. You will need to determine if the noise is occurring from the recirculation doors opening and closing, change in temperature or change in direction of airflow. Some vehicles will have two separate doors to control air flow.