I searched the forum and did not find a similar problem.

Vent fan on lowest setting, air blowing normally, then a clicking noise starts like someone put a piece of paper in the fan blades. Noise seems to be from passenger side by feet.

Vent fan up next highest setting, clicking noise increases in speed to match the fan.

Turn vent fan off. Wait a minute. Turn back on lowest setting. Blows air normal and quiet for 30 seconds and then the clicking noise starts again. No increase or decrease in fan force when clicking noise happens.

Adult driven car, no children to throw things in the vents to make noise.

Drive home from work today and no clicking noise for 1/2 the trip, then it started.

Is there more than one fan? Seems odd it is an occasional problem, but once it starts, it does not stop unless you turn the fan off.

Very noticeable at low fan speeds, not noticeable at high fan speeds.

Any help is appreciated. Thank you.

 

Sounds like a leaf may have gotten in to the air duct.
I'd take the cabin air filter out ( located on passenger side by feet, coincidentally) and see if you can find it.
I can't recall where the air intake ducting is under the hood, but you may have to remove it and clean it out there

 

I had a similar issue that also involved a strange smell. Turned out we had a mouse that filled / packed the cavity in the fan assembly below the filter with small dog biscuits we had been keeping in the garage. This was on Sweeties (the boss) Hyundai Entourage.

We changed our storage techniques.

 

I do not have a cabin filter in my bare bones model. I will have to find the air intake under the hood and see if I can reach down or stick a vaccum hose down there.

My memory was jogged to my childhood. We had a Blazer that the mice were fond of and packed it full of dog food so I am familiar with the problem. Thanks for the reminder to check out the simple things first before I start replacing fan motors.

I wonder what it is about cabin filters and ductwork for mice that draws their attention.

 

I had a similar problem also involved a strange odor. It turned out we had a mouse that is packed under the hood cavity filter with a small dog biscuits that we had been in the garage. It was a candy Hyundai Entourage.

 

What does this have to do with the OP?

I also had this problem just the other day. I just turned it low to high a couple times and whatever was in there blew out and the noise quit!

 

I have a 2006 Chrysler Pacifica. Recently I turned the heater on and heard a thump. When I turned the air off and on again, something was clearly blocking the blower fan/motor. There was air but I didn't like the noise. I knew it was either a rodent or its nest because my husband had this issue with his truck. As we all know, this vehicle is hard to disassemble but after removing the glove box we saw a tiny bit of fur hanging out of the front blower motor vent directly up/under the right side of the glove box. It was tight but we removed the screws around the blower motor vent and pulled the plastic vent cover down enough to remove the mouse and clean with bleach water and lysol..lol. We cracked the plastic in the process because there was one screw in the very back too difficult to reach. But it won't be an issue. The odor is not too bad and should eventually dissipate. It was very frustrating not being able to find a forum with similar rodent issues explaining where to look and how to remove, etc. FYI, a Chrysler dealership wanted $170.00 for labor only ...ugh. Also we removed the air filter and found acorn shells and debris. And we found the rodents had eaten the plastic part of (under hood) dash cover at the end of each window wiper so they can enter that way too...I placed a small amount of steel wool in those areas (being careful not to block anything but rodents). Not sure (yet) how to prevent from entering into air filter, vent ducts or under vehicle in general. I hope this is helpful.