03/2004 MCS

I've got an intermittent HVAC-related noise I've been trying to figure out. It sounds like a dry, failing bearing.

The attached recording was made sitting still with the engine off. In the middle of the recording I momentarily turned the blower off, then back on.

It's hard to locate exactly where it comes from but seems to be from the center console or passenger side. As I said it is intermittent. When it does it, it is usually worse under braking/deceleration. It only happens with the HVAC blower running. It will do it with the engine running or off. It is independent of road speed. It is independent of blower speed. When it is making the noise, the pitch never changes. If I had automatic climate control, I would think it would be the aspirator motor for the temp sensor. However I do not have automatic climate control, I have manual climate control.

This is my DD so before I start taking everything apart I'd like to have the replacement part on hand. I have been through the HVAC exploded diagrams at RealOEM and cannot find anything that would be a candidate for what I'm experiencing. Anyone ever run into this before? What was it?

Thanks!

 

Before you go and pull the hvac unit try to blow air with a compressor into the vents or perhaps use a vacuüm machine to suck. IThe whirring noise could also be a small leaf or debris rubbing again the fan.

You do not want to pull the hvac just for fun because it is a lot of work. I did a small write up about it as I needed to replace the evaporator.

 

Just thought about this now: open up the cabin airfilter compartment and stick a vacuüm cleaner in there. That's going to be way more effective then using the vents as the motor is practically next to the cabin airfilter.

 

Thanks! It's not the main blower because the sound doesn't change as the blower speed changes. However, cleaning in there is probably not a bad idea!

That said, looking at your photos I can't see any other candidates for the source

 

What is this?

 

A plug for the hvac loom. Basically the hvac loom can be separated from the main loom.

 

Oh ok thanks. I was hoping it was some kind of little motor!

 

On the climate control ac there are little motors (I think they are called acruators?) but the manual ac everything except for the blower motor is mechanical. The temperature **** controls a flap using sticks and the blow direction controls a bowden cable. Pretty neat.

 

Right that's what's confusing me. I've seen the back side of the control panel years ago when I put in a stereo head unit and I didn't recall any motors on it, nor could I think of why it it might have one. A source of the sound that would make the most sense to me given that it never changes pitch would be an aspirator motor that draws air over a temperature sensor for automatic climate control. But I don't have auto control! If it is indeed the main blower then I'm baffled by how the speed of the blower can change without the pitch of the noise changing!