Cycling noise in dash/HVAC panel

[aaaaah]

I did a bunch of googling and either couldn't find the right words to search it or just couldn't find a similar post but...

I have a 91 325i and from within the HVAC panel is a noise that sounds like something cycling/rotating continuously at a slow speed. A bit like a CD ejecting but not that, I've been jokingly describing it as the gears inside the 6 button MFC for the clock.

It happens no matter what I set the HVAC controls to but it does change pitch when I put the system into recirc. Any ideas?


Also, whenever I have the faceplate in my crappy aftermarket stereo a whistling noise comes through the speakers that varies with RPM. My assumption is that the head unit was just wired in poorly.

Any help would be much appreciated.

[ST1G]

Also, whenever I have the faceplate in my crappy aftermarket stereo a whistling noise comes through the speakers that varies with RPM. My assumption is that the head unit was just wired in poorly.

Probably. The head unit is probably picking up signal from a wire that is grounded on accident. I use to get this noise if I let the Aux cable touch the seat rails on accident. Took me a hour to figure it out.

A video of the noise in the HVAC would be helpful.

[aaaaah]

Probably. The head unit is probably picking up signal from a wire that is grounded on accident. I use to get this noise if I let the Aux cable touch the seat rails on accident. Took me a hour to figure it out.

A video of the noise in the HVAC would be helpful.

I'll take a video of the HVAC noise over the next day or so!

[aaaaah]

Ok, I uploaded a video of the noise. The car is off with the ignition set to on, fan is off. The noise doesn't change no matter what you do with any of the controls but does change pitch if you select recirc.

[mikerob97]

There are two small motors attached to the HVAC box behind the dash that move two recirc flaps. I have seen these flaps break in the past and the actuation rods just flop around. It may be that one of these little recirc motors is broken and just spins. If you remove your radio, you may be able to put your fingers on these motors and feel them vibrating / moving. This is a bit of a longshot - but since you mentioned that the noise changes with the recirc switch position, thought it may be a place to look.

Let us know what you find...

[aaaaah]

There are two small motors attached to the HVAC box behind the dash that move two recirc flaps. I have seen these flaps break in the past and the actuation rods just flop around. It may be that one of these little recirc motors is broken and just spins. If you remove your radio, you may be able to put your fingers on these motors and feel them vibrating / moving. This is a bit of a longshot - but since you mentioned that the noise changes with the recirc switch position, thought it may be a place to look.

Let us know what you find...

This actually fits the sound it's making perfectly. I'll be looking at replacing the head unit and getting an analogue clock in the near future so I'll have a look then. At the moment it's more of a nuisance more than anything.

How serviceable are the flaps/assemblies?

[mikerob97]

I have owned two E30s and on both cars, both flaps failed in exactly the same way. The point of attachment of the actuator rods breaks off of the flap. Since I really never use the flaps in the recirc mode, I never attempted a fix. Instead what I do is remove the actuator motors and the rods (since the rods are bouncing around under your dash). Then I remove the HVAC fan cover from under the hood and lock the flaps in the open position - which is the no recirc position. You will here a light snap, as the flap moves to a detente position and stays locked in place - almost like the flap was made to lock in an open position perhaps on non AC cars with out the recirc feature. Now just replace the fan cover - and you are done. You will not have to worry about this again. In NY, your AC should work just fine in the summer months in the non-recir position.

Make sense?