Got off work today, -20, went to turn my heat on, and all I could hear was a really harsh grinding noise coming from what seemed to be near the underneath of my stick shift. First off my heat was only blowing defrost, no matter what setting, but now it's making a terrible noise and I can't even have it on! I kinda need heat since winter just came in, so if you have any tips please help! thanks!

'93 f-150 XL, 4" lift, 33's.

 

Sounds like the blower motor - was it still putting out air? Sometimes the wheel will rattle a bit but still blow air. If it's not working at all, a replacement is fairly cheap, and easy to get to inside the engine bay. (at least that's the case on my 91 - your 93 might be different?)

In order to get the diverter fixed (and send heat wherever you want it), you'll probably need to track down some vacuum lines behind the dash.

 

Seems to me that if air is still comin out, then the motor is still at least partially workin. The grinding sound coming could be something in the motor having broken loose and getting caught within the motor itself. In relation to the stuck diverter, I would check to make sure everything is still hooked up properly. Move the selector around and see if you can hear anything moving with it. Check the connections then go from there.

 

Mine's been rattling since I got the truck 2-3 years ago. Still blows air, and I've had more pressing issues with the truck, so I never swapped it yet. If it ever locks up completely, it'll move to the top of my list!

 

mine stops blowing when i speed up. at a idle or stop it blows fine.

 

Turns out that if it's cold, the heat will only blow if it's cranked, other than that it'll make the noise. There's a T that connects the vaccuum lines to blow the air out the vents, and that had come off one of the lines, which made it only able to blow out the defrost. Thanks for all the help.