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2009 Blazer a/c stuck on defrost

debbiecampionedebbiecampione Posts: 2
edited March 2014 in Chevrolet
Hi, my problem is that my switch to change from a/c, heat, def., when I use the blower it always come out of defrost and the floor. How do I fix this, where do I start?


  • jlflemmonsjlflemmons Posts: 2,242
    First thing to check is the vacuum lines coming from the intake manifold, to the A/C controls, to the vaccum resivoir. Lots easier than it sounds!

    The hose comes from the intake manifold (top of the engine) on the drivers side toward the rear and goes across the power brake booster. The booster is a large (~12" in diameter) round metal object mounted in the engine compartment right in front of the driver. The hose goes to a "T", with one side going on to the resevoir in the drivers front fender, and the other side going to a vacuum line down below. Both are easy to get to, and will probably be dried out and cracked. This is very common, the vacuum lines are available at any auto parts store, and shouldn't cost more than a couple of bucks. Takes about 10-15 minutes to fix.
  • :confuse: My IAT Sensor is causing my check engine light to come on. Does anyone know where this is located?
  • Hi there my problem is when i try to use the heater and try to chage it to defrost or front only or for the floor does not change it only stay in dashboard mode only .Is a 2002 LS Blazer .I check the hoses and there are new .Also while on heat mode the ac compressor turns on and off
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