Need help determining cycling solenoid

Turn up the radio and don't worry about it.

 

There's a video attached to this thread with the sound of a noisy HVAC servo, in case it might be that.

The video is actually attached to the thread (not hosted on a media site) ... can be downloaded, unzipped, and played.

-Chap

 

I used to know an idiot who really thought that way. I guess your commenting tongue in cheek?

So it shouldn’t actuate until a HVAC change was made, or ignition ready?

 

The HVAC dampers are positioned by servos—that is, actuators with built-in position sensor feedback. The ECU knows where it wants the position to be, so if the sensed position is different, it drives the servo toward the desired position.

When the position sensor gets old and electrically noisy, it's as if the ECU is seeing the damper position constantly jumping around. So the ECU keeps constantly driving the actuator trying to get the position back where it should be. So no, it doesn't depend on you making any HVAC change.

-Chap

 

You may actually find some play in the linkage. Fortunately I have bad hearing, so everything works perfect, I don’t even have to turn my radio up, to drown out the knocking engine.

 

TY You already have.

 

I've just added this same note on my original thread:

For future reference, the Gen 3 Prius replaced these actuators having potentiometer-style feedback with a new design using Hall-effect sensors for the feedback. So this should be a very uncommon issue in Gen 3 or later. Gen 1s and 2s are likely to experience it as they age, and as you can see, it's very easy to fix.

The one exception might be if the air-inlet damper is the one that gets noisy. The other two servos (air mix for temperature, and outlet select) are on the easy-to-reach side of the heater case. The air inlet one is much harder to reach on the other side of the case, sandwiched between it and the blower. The dash might really have to come off to reach that one. I never had to do it (had my Gen 1 up to 230,something thousand), but it is built the same as the other two, so somebody keeping a Gen 1 or 2 super long might eventually have to deal with it.

-Chap