Mk1 Focus HVAC noisy after installing cabin filter

[tommygunn]

The US-market first-gen Focus didn't come with a cabin air filter from the factory, but the provisions for the filter are still there, the empty box where the filter sits.

Anyway, after installing the filter, now the heat/AC is noisy on the higher fan speeds. Kind of like a groaning noise, somewhat like the engine at higher rpm. The fan noise is proportionate to the fan speed; that is, no noise when it's off or on 1, slight noise on speed 2, and very loud at 3 and 4 (there are four fan speeds for the climate control, marked 0-4, 0 obviously meaning off)

The heat still gets hot and the AC still gets cold. There is no other problem with the HVAC system except the noise at the higher fan settings.

 

[CHARLIEBRONSON21]

Cavitation maybe?

 

[The_Jeff]

The fan blades are pulling the motor shaft against its end bushing/ bearing harder than before.

 

[CT8]

Originally Posted By: eljefino
The fan blades are pulling the motor shaft against its end bushing/ bearing harder than before.
Back pressure?

 

[charbaby]

Uninstall!

 

[jmb3675]

I had one in my focus for a while over the summer. It made the fan almost silent. Unfortunately it also reduced the speed of the air by about half. I couldn't even get the back seat cool so I took it out.

My fan made a groaning noise on high before the bearings failed. That was about a month before I tried the filter though.