Problem with air circulation system

Hello,

I have a 2003 Silverado truck. I am having an ongoing problem with the air circulation system, and have had my truck to 3 shops so far. Any help in diagnosing and resolving this problem will be greatly appreciated.

At any setting or temperature, after running for about 20 minutes, the fan (?) will start to make a significant noise. Its a rumbling noise which comes from the passenger side of the dashboard. When it makes the noise, no air comes from the vents.

Its not a clicking noise, but sounds like something is stuck in or is blocking the system. I turn off the fan, wait 10-15 minutes, turn it on again, it runs fine. A short time later, the noise returns and air is blocked again.

The last shop (Chevy dealer) "dropped" the fan, and could see nothing wrong. What should I ask shops to check?

Thank you!

It sounds like the blower motor is toast. Did the shop run it for 20mins? Or just pull it and look around? Usually when blower motors start going bad they will squeal somewhat. The internal bearings are dried out thus the noise. Once it is dry, it will overheat the motor and seize. Then after it cools down, starts working again. Until eventually it burns up the motor.

The shop has claims to have previously run the system for an extended period of time. This last time, they said they just pulled the fan and looked at it. this noise does not sound like what I would normally associate with bad bearings. Its definitely not a squeal. Its a rumbling or roaring noise. Would failing bearings make that kind of noise?

The shop has claims to have previously run the system for an extended period of time. This last time, they said they just pulled the fan and looked at it. this noise does not sound like what I would normally associate with bad bearings. Its definitely not a squeal. Its a rumbling or roaring noise. Would failing bearings make that kind of noise?

the fan making noise , then no air is a bad fan motor. buy a new motor and replace the air filters if your vehicle has them. I think your vehicle does have air filters in the air box next to the blower motor. the dealership at times are not up to speed on these things like electrical motors. this motor has no bearings just a bushing. the motor windings when this old crack ,then the motor has internal shorts that cause the motor to heat up the it makes noise and then binds. I just love it when members say they could not find any thing ... well bring it in when it screws up. have the service manager look at it when it craps out. when you go to the dealership what they may say is purchasing a new vehicle will fix your issues. or they will charge you so much that you may think they were correct . any non dealership, auto servicing repair shop especially , an ac shop will fix this cheaper and with no nonsense.