When I turn my fan on with either the heat, outside air or the ACrunning it blows fine in the first 3 settings but the highest setting it stops blowing air all together. Not even a little bit of air comes out. I had this same issue with my 2000 GMC Sierra and never looked into it. Is this a common issue with GM and how can I fix it?

 

I'm going to assume you have the manual climate control and not the automatic. Also, please put your vehicle information into your siganture and attach it to any tech help post so we don't have to go looking around for that information.

Here is the diagnostic trouble shooting steps for a high fan inoperative issue:

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