98 Yukon heat / AC vent control doesn't work

[ifixedit]

Hi all,

 

Well, now that I've hopefully solved one problem (with my 03), I now need to try figure out what the deal is with my old 98 Yukon. When using the heat / ac and you turn the dial to select floor, dash vents, defrost or whatever it results in very little change and the air is pretty coming out of all of the ducts, kind of like central air! ;-)

 

I read elsewhere that there's a vacuum line I should be looking for that is likely leaking but I can't find one anywhere coming off the engine and going to the firewall, in fact I haven't found a vacuum line of any kind coming off the engine period, leading me to think the previous info I read is incorrect. In the case of the 98's I'm guessing it's perhaps an issue with a motor that does the job of changing which vents the air comes out of, but I'm not sure.

 

Any ideas where I should be looking to find and fix this problem?

[1997SierraSLT]

There is no vacuum line. It's all controlled by a blend door actuator motor located on the left side up under the dash (directly below the left edge of the radio).

 

The linkage & elliptical spring gets gummed up on the actuator linkage mechanism.

[ifixedit]

Thanks! My next step was to take a look under the dash for a motor or some type of linkage that moves, but had no idea where to start looking or what it looks like. Should be able to locate it now and maybe a shot or two of WD-40 will cure it. It does act like it's stuck or barely moving. Should be able to get at it tonight and will let you all know how it turns out.