Blower stuck on defrost


Jan 21, 2006
Hey guys, need a little help. The blower motor won't change from defrost to vent or floor. Any ideas on what is wrong with it would be greatly appreciated.
there is a vacuum switch behind the AC/heat controls.. I got one from highway stars for like 14 bucks.. instantly fixed the problem.. also check the vacuum tee back by the firewall, if that goes, it blows out the swith behind the controls. I had the same problem, only defrost even in AC mode.
One idea to check if the vacuum system checks out.

Once the engine is shut off, the vacuum bleeds down and the HVAC defaults to defrost. On quite a few cars I've discovered the foam seal on the diverter flap has degraded, leaving the sticky glue to effectively glue the door shut. If you are lucky, you might be able to pull out the center vents and pry open the door with a small flat file or dental pick. I ended up inserting a temperature probe in the vent to prevent the door from closing, I haven't gotten the energy to pull the dash apart to do a proper fix.
Is there a hiss under the glovebox? There are two ports through the firewall that can get unplugged- mine did that once. You can follow the vacuum lines from the a/c heat controls to those ports.
Would like to thank you guys for the help. Checked under the hood and found a broken line on the tee under the EGR valve. Replaced that line this evening and fixed the problem. Think I will go to the auto parts store and buy new hoses so I can replace the rest of my old vacuum lines. Thanks again for the help!!!!