Sudden vibration/noise from blower motor (VIDEO)

[AVR2]

So all of a sudden, the blower motor in my 2005 KJ is vibrating and making a really objectionable noise when the blower is on 4 (which it needs to be during the summer). It can also start making the noise when it's on 3 and the Jeep goes over a speed bump or similar.

I've had the motor out, and I can't figure out why it's suddenly doing this. The HVAC housing is solid, there's no looseness or movement at all there. If you grab the base of of the motor when it's installed, there's a small amount of rotational play (see video below), but after removing and replacing it multiple times I can't find any way round that. That *seems* to be the way it's supposed to be.

If you run the blower on 4 when it's removed from the housing, it sounds totally normal, so I don't think it's anything related to the internal mechanicals of the motor itself. It's not anything rattling in the glovebox either, because it makes the same noise with the glovebox removed.

As you can see from the video, if you press upwards on the base of the motor when it's running, the vibration stops. But that's obviously not an option during normal driving.

VIDEO: Blower motor vibration

 

[uss2defiant]

try putting a shim between the motor and the dash which it mounts to.

 

[AVR2]

There's no space for one. I've looked for places where I could attach foam tape, but there are none. Anything you put between the motor and the HVAC housing will prevent it attaching to the housing.

 

[uss2defiant]

Have you tried thin plastic shims?
ie the plastic cover on the box when you buy some things.

 

[CactusJacked]

Did you look at the housing for any shiny or worn spots to see if the fan is rubbing against the opening, or on the back side? Sounds like fan blades riding against plastic.

 

[AVR2]

The blades aren't touching anything. It's just a vibration between the blower and the HVAC housing.

 

[libertybob]

vibration

Some fans have a small balance weight on them that can cause serious vibration if they come off. Don't know about Liberty fans but sudden occurrence suggests this. Once had a Pontiac Fiero that slung the balance weight on the radiator fan and the resulting vibration shook the whole front of the car. A fan blade out of balance causes a lot of vibration. One more thing to check.