Loud brrr/vibration on start (AC related)

[marleysbeard]

Hopefully this is the right spot for this. Basically if the AC is on when I turn the Tahoe off, when I turn it back on I get a brrrrrrrrr sound for about 5 seconds and then it goes away. I will hear it occasionally after that but it doesn't seem as noticeable as that first time. I'll try to include a video that captured the initial noise after start up.

So far all I've done is pull the blower out and make sure it was clean but that didn't resolve the noise.

https://imgur.com/a/l7RcQo6

Side question, do I need the engine air filter "with off road package" on a Z71? Looks identical to the "without off road package" filter in the picture online.

 

[marleysbeard]

Should've mentioned the AC works great, blows hard and cold.

 

[swathdiver]

Hopefully this is the right spot for this. Basically if the AC is on when I turn the Tahoe off, when I turn it back on I get a brrrrrrrrr sound for about 5 seconds and then it goes away. I will hear it occasionally after that but it doesn't seem as noticeable as that first time. I'll try to include a video that captured the initial noise after start up.

So far all I've done is pull the blower out and make sure it was clean but that didn't resolve the noise.

https://imgur.com/a/l7RcQo6

Side question, do I need the engine air filter "with off road package" on a Z71? Looks identical to the "without off road package" filter in the picture online.

The sound may be related to a condition called "slugging". @gooffeyguy

The Z71 air filter may be thicker to be used in dustier conditions. I run them in my truck and of course, they last much longer.

 

[marleysbeard]

The sound may be related to a condition called "slugging". @gooffeyguy

The Z71 air filter may be thicker to be used in dustier conditions. I run them in my truck and of course, they last much longer.

Gotcha, I'll look into slugging and go for the Z71 filter. Thanks

 

[OR VietVet]

Yea, I was gonna suggest comparing filter measurements and should do as @swathdiver suggested.

That noise could be an actuator and initially I thought it could be fan/blower. Did you start up and still hear noise with blower removed? Check to see if the blower wheel was touching anything? But, could also be related to the compressor "slugging". Have you listened under hood while someone else starts engine? Only happens with a/c on? Ever happen with a/c turned off?

 

[swathdiver]

Gotcha, I'll look into slugging and go for the Z71 filter. Thanks

I run the A3085C, that number has been replaced by another now.

 

[marleysbeard]

Yea, I was gonna suggest comparing filter measurements and should do as @swathdiver suggested.

That noise could be an actuator and initially I thought it could be fan/blower. Did you start up and still hear noise with blower removed? Check to see if the blower wheel was touching anything? But, could also be related to the compressor "slugging". Have you listened under hood while someone else starts engine? Only happens with a/c on? Ever happen with a/c turned off?

So went out and messed with it a bit more. It did make the sound with the AC off although it wasn't as noticeable. It also seems to be much louder after its been sitting, as in the video example I shared. Had my wife start it and I was not able to hear it from the engine. I didn't try it with the blower wheel removed, would the wheel move with the AC off? Also I'd think the noise would be constant?

 

[OR VietVet]

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.

 

[corvette744]

Unplug power from blower motor and try that.If still their then you need to determine if its under dash or in engine bay-might have to stick your head under the dash when its happening.

 

[marleysbeard]

Unplug power from blower motor and try that.If still their then you need to determine if its under dash or in engine bay-might have to stick your head under the dash when its happening.

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.