A/C and Heater has low volume of air being pushed through the vents?

2004 CHEVROLET SILVERADO
140,000 MILES • 4.7L • V8 • 2WD • AUTOMATIC
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JR PAYNE
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  • 47 POSTS
My truck has had this issue since i purchased it a few years back. When i turn on the AC and or the Heater the airflow is minimal. I have tried to turn on the recirculation and no help either. In all positions it seems to have a low volume of air being pushed through the vents. Any ideas? Thanks in advance.
Jul 6, 2023 at 1:29 AM
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MATHGEN
  • Experienced Mechanic
  • 128 POSTS
Do you notice the blower fan changing speeds with each increase or decrease in setting? If not, you most likely have a failed blower motor resistor. If the fan speed changes, then there may be a restriction or blockage in the housing or duct work.

We once had a similar issue and the technician finally found plastic grocery bags stuffed in behind the vents.
Jul 6, 2023 at 11:24 PM
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JR PAYNE
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  • 47 POSTS
Interesting. I will check the resistor and report back to you on what i find. Thanks again much appreciated.
Jul 7, 2023 at 4:07 AM
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JR PAYNE
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  • 47 POSTS
I checked the fan speed and you can definately feel the difference in the speeds.
Jul 7, 2023 at 2:51 PM
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MATHGEN
  • Experienced Mechanic
  • 128 POSTS
Thanks for the update. It sounds like you may have a restriction somewhere. Sometimes the fins in the heater core and evaporator coil can get plugged up, especially if the vehicle was run a lot in dusty conditions. You can check airflow with a smoke pencil or incense stick. Run the blower on high, recirculation set to fresh air and hold the smoke near the recirc inlet on the passenger side under the hood. Look to see how fast the smoke is pulled in. Or you could remove the blower motor and inspect for dirt, debris, etc. If you have a borescope, you can snake it through the vents and look for a problem. Let me know what you come up with.
Jul 7, 2023 at 9:39 PM
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