I am having this loud buzzing that I believe is coming from a fan next to the heater core on the passenger side of my truck. I believe this is a fan because it is not specific to AC or Heat. If the fan is kept low it may not occur, but if I turn up the fan higher it kicks on and stays on. Once this buzzing occurs I no longer have control over level of the fan, I then have to turn it down, turn off the truck to reset. I'm thinking its some kind of a switch that I'm having trouble with.

 

Possible blower motor resistor?

 

I pulled the blower resistor but I didn't see anything wrong with it no corrosion or anything. Any other ideas? Here is a video of my issue.


http://www.youtube.com/watch?v=ia0JlJyP6lg

 

Still having this issue, no one has had this huh?

 

My 2013 F150 XLT started having the same issue a few days ago. The first few times I could restart the truck and the fan would work ok for a while longer. Now the fan cuts out and the buzzing starts after a few seconds of turning the AC on, just like in your video. The buzzing persists even if I turn off the AC controls, and doesn't stop until I restart the truck.

Any luck fixing yours yet? I just started researching so I'll report back if I find a solution for mine.

 

I don't think the 2013 has a resistor, it has an electronic module.

 

Well I ordered a new motorcraft blower motor control module. Replaced it this evening, and the problem is unchanged. The fan will respond normally to changing the manual fan speed controls and the AC blows cold, but after a few seconds, the fan speed goes way down, does not respond to controls, and the buzzing noise starts. Having my head down there, it kinda sounds as if the blower fan motor is seizing up, and it seems like that is where the vibration is emanating from. So I pulled out the blower fan to inspect it. I did not see anything that looked abnormal. Nothing was loose, no debris, etc. I held the fan outside of its housing, in the footwell under the dash, turned on the AC and let the fan run on high for about a minute... it ran fine and the buzzing did not start up. I put the fan back in, turned everything on, and the buzzing and low fan speed issue started up after a few seconds again.

Anyone have any thoughts for plan B??

 

No idea I just have had my fan below the threshold of where the buzzing comes on. At some point I may bring it in.

 

I did some more work on mine. Checked the blower motor relay and fuse, and switched them with other identical ones to confirm they weren't the problem. I figured the last step before taking it in to the dealer was to replace the blower motor itself. I wasn't convinced that was the issue, so I got a used one for $30. Turns out that was the issue. Fan works great now and I had it running on high for about half and hour just now.

Good luck with yours deific. My issues were identical to what you described, so I hope this helps.

 

So it was the blower motor relay and the fuse that you replaced?

 

No, I replaced the blower motor. The actual fan assembly under the dash.