Hi, welcome to the site.hi, great forum, thanks for all the great info. i hope this thread is the answer to my problem and i hope others can give me ideas.
2003 sle envoy. i recently (well last few months ) am only able to have A/C or heat come out of the front vents on the 3rd setting on the nob. A/C and heat works but only blows out strong on 4th and 5th setting and NOW today only on the 5th setting. before i had the battery die and had throttle problems and was able to fix it with a good cleaning of it...thanks to the forum. do you think its the " mode door actuator " that needs to be replaced? i too have had the clicking sound but strange as it might be only time i hear it is during the winter months. thanks for any help and great forum with great info.
The mode doors only control the direction of the air flow (floor/vent/dash), have nothing to do with the fan speed.
It sounds like you are having a problem with the fan speed control module. I think it's called a blower motor resistor assembly. Very common problem, it's a $25.00 fix (if u do it yourself) and located under the dash, behind the glove box. Lots of info on here, and some pictures. Try a quick search, the more recent threads are the ones to view.
You may also have a mode door problem, but the speed thing is the resistor assembly.