buzzing noise from heater?

my 1989 GMC k1500 stepside makes a buzzing noice when i run the heater, when i turn it up the noise gets louder, whats causing this and how do i fix it?

my 1989 GMC k1500 stepside makes a buzzing noice when i run the heater, when i turn it up the noise gets louder, whats causing this and how do i fix it?

Could you be more specific? Does the noise get louder when you change the fan speed? Or is it when you adjust the temperature for more heat?

//2000CAYukon

Could be some leaves or like in my case, pine needles get in there and ratchet on the blower cage.
Mine eventually ground away.
Bob B

Yeah my 1994 Gmc Sierra does the exact thing when i turn the heat to a higher speed. I dont hoenstly know what it is and i havn't checked if there were anyting stuck in the cage but i will. Hopfully someone knows what may cause this i though it could just need oiling? But i dunno gotta wait to summer to find out.

I NEED HELP TOO!

I had a 2000 GMC Sierra that had the same problem. It turned out to be a really dirty "cabin filter" was causing the fan to make the noise due to strain. Don't know if your year truck has a "cabin filter" but if it does, change it out and I'll bet the problem gets solved.

I had a leaf get down into the cage and it made a lot of noise. I pulled the blower motor and cleaned out the leaf.

No cabin air filters until 99 NBS.

//2000CAYukon

I have a 2000 GMC sierra 1500 and I have heard that same humming noise while the heat or A/C was on. The noise also got louder when i turned the dial to a higher speed. So I took the blower motor out and found 2 leaves in it. Then I took the leaves out then put it all back together and it works perfectly. I hope this helps somebody because I was very frustrated with it. Thanks