Loud brrr/vibration on start (AC related)

[swathdiver]

The wheel may move with a/c off if system faults to a vent mode but I do not know for sure.

I recently experienced the same thing, with my a/c off, and I think it is an actuator noise or a small fan related to a cabin air temp sensor. My noise was only around for 3-4 days and was very intermittent and is now gone and did sound just like your sound. It was definitely on the P/S and seemed down low.

Yeah, I just saw the video and listened, sounds like it's in the dash. Would like to see what the actuators are doing with a Tech-2.

 

[marleysbeard]

Yeah, I just saw the video and listened, sounds like it's in the dash. Would like to see what the actuators are doing with a Tech-2.

You think an auto parts store code reader would get a code or would it need to be the Tech-2?

 

[OR VietVet]

Didn't happen as quickly and was shorter in duration but I got the same noise with the blower disconnected. Going to drag the wife back outside to start it for me while I listen underneath the dash and see if I can get a more specific source location.

Appreciate the help. Would love to be able to fix it myself but if I cant track it down I'll take it in. Just want to catch whatever is happening before it gets worse or causes problems elsewhere.

I am gonna watch for sure because I HAD that same noise. remove the glove box for better access.

 

[corvette744]

Didn't happen as quickly and was shorter in duration but I got the same noise with the blower disconnected. Going to drag the wife back outside to start it for me while I listen underneath the dash and see if I can get a more specific source location.

Appreciate the help. Would love to be able to fix it myself but if I cant track it down I'll take it in. Just want to catch whatever is happening before it gets worse or causes problems elsewhere.

You wont have to take it in you can find it.Determine if its under dash and were or if engine bay maybe remove ac belt and start it.If under dash your hand should feel the vibration or shudder noise-Hell maybe a blend door or other door is sticking in the heater box assy.

 

[marleysbeard]

You wont have to take it in you can find it.Determine if its under dash and were or if engine bay maybe remove ac belt and start it.If under dash your hand should feel the vibration or shudder noise-Hell maybe a blend door or other door is sticking in the heater box assy.

It's been a bit difficult to locate because its so inconsistent and brief. Gonna mess around with it some more now that I'm back at home. The wife swears it sounds like a fan. But I know its not the blower and I don't think there is any other fans under or around the dash.

Driving it home just now it was doing it off and on though not as loud/long as the video. I turned off the AC and it went quiet. Odd that it did it without the AC on when I tested it while parked earlier but stops when I turn the AC off while driving.

 

[swathdiver]

You think an auto parts store code reader would get a code or would it need to be the Tech-2?

No, those internal codes are read by a bi-directional scan tool like the Tech-2. As I think of this more, I bet it's an actuator because they self-calibrate every time the vehicle is started (or some schedule like that). So what you may be hearing is are broken gears chattering in one of the actuators; they're plastic. If you put your hand on them when the key is turned on, you can probably deduce which one is making the noise.

The mode actuator is in the driver's footwell behind the center console.

The driver's side temperature actuator is in the passenger's footwell under that plastic cover near the console.

The passenger's actuator is about a foot directly above inside the dash, and the recirc is a few inches to the right and upright.

 

[marleysbeard]

No, those internal codes are read by a bi-directional scan tool like the Tech-2. As I think of this more, I bet it's an actuator because they self-calibrate every time the vehicle is started (or some schedule like that). So what you may be hearing is are broken gears chattering in one of the actuators; they're plastic. If you put your hand on them when the key is turned on, you can probably deduce which one is making the noise.

The mode actuator is in the driver's footwell behind the center console.

The driver's side temperature actuator is in the passenger's footwell under that plastic cover near the console.

The passenger's actuator is about a foot directly above inside the dash, and the recirc is a few inches to the right and upright.

Would there be a noticeable symptom in regards to ac/heat settings? IE it wont switch to floor or defrost or wont switch to heat?

I'm not very experienced this stuff so looking underneath the dash I just see a lot of black plastic and I'm not really sure what I'm looking at.

With my head down by the pedals it sounded to me like it was coming from back behind the center console. When I listened on the other side it was a little less clear but it seemed like it was coming from the center of the passenger footwell, low and all the way back against the wall.

 

[swathdiver]

Would there be a noticeable symptom in regards to ac/heat settings? IE it wont switch to floor or defrost or wont switch to heat?

I'm not very experienced this stuff so looking underneath the dash I just see a lot of black plastic and I'm not really sure what I'm looking at.

With my head down by the pedals it sounded to me like it was coming from back behind the center console. When I listened on the other side it was a little less clear but it seemed like it was coming from the center of the passenger footwell, low and all the way back against the wall.

Not necessarily. This is what the actuators look like and this is where it is:

In the photo immediately above, the driver's side actuator is directly below the passenger's about a foot down if you follow the wiring. Access to it is under that black flexible cover above the passenger's feet.

 

[marleysbeard]

I tested every single climate function today. All of them worked as expected minus one. The 2nd row overhead vents don't blow hot air. They will blow cold AC but when turned to heat they blow neutral, not hot or cold. I don't know that this would explain the noise but maybe I'll get lucky.

 

[gooffeyguy]

Maybe I missed it, but do you have the manual HVAC controls or the automatic? I don't know if both were available in '04 or not. My '01 has manual controls