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HVAC Control Ignores Dual Temp Setting

I have a 2000 Buick Century Custom.
(I tried to enter this into the vehicle make and model dialog boxes at the beginning of this post but it won’t work for me, although I got make and model into optional tags box .)
It has the automatic HVAC Climate Control. Everything seems to work fine, except I don’t remember the dual control ever working, I haven’t actually tried to use it. But I recently had the refrigerant recharged and in testing operation of the A/C, found that the dual control doesn’t work, it will not modulate the temp in either A/C or heating for the passenger side, keeps the discharge air temp the same as driver’s side. A short while ago, I heard clicking sounds that would make it seem like the door actuator motor for the passenger side is stripped inside. So I’m wondering where would I find this actuator 2 take it apart and confirm it is the problem, or a problem that needs to be dealt with. A youtube video showed how a 2004 GMC Denali only needed to have it’s HVAC control panel reset by turning ignition on, pushing “auto” button on HVAC control panel, turning key off, removing 10 amp “HVAC ECAS” fuse for 1 minute, reinstalling, running engine for 1 to 2 minutes, shutting engine off for between 10 and 30 seconds, restarting and checking control operations. This was said to work for GM vehicles maybe as early as 1999 to vehicles several years later. But I have several HVAC fuses, none saying “ECAS” or labeled in a way where I would think I could reset the HVAC controls by removing fuse, starting and stopping engine and refitting that fuse. Might there be a way I could try this, though, before diving in to remove the actuator if I would be able to get at it as a DIY class only mechanic? And of course, also would someone tell me where the dual control actuator is, and how to get at it, what must be removed?

Sometimes removing the glove box makes access to actuator easier.


Thanks much, Tester, for this good diagram! I’m hoping this air temp actuator (#2) would be the actuator for the passenger side only, which is where my no temp modulation problem is…