Truck heater question

Discussion in 'The Lounge' started by hahner724, Jan 9, 2009.

  1. My truck heater blows heat out when it is on defrost, but when i turn the knob to the heater or vent nothing comes out. It is a 2000 GMC Sierra if that helps out. I was just seeing if anybody knows what could cause this and the solution. thanks
  2. BigV

    BigV BigV

    Sounds like the heater control actuator.
    It’s a little motor that moves the door for your heat control from defrost to vent or heat. It’s usually located behind the dash and is a PITA to get to.
    Sounds like it’s stuck in the defrost position. My wife’s Ford stuck in the off position so she had no heat at all.

  3. My 2001 silverado only works on the 4 and 5 spots for the fan.Maybe a gm thing.
  4. freyedknot

    freyedknot useless poster

    if it only come out of the defroster ,but nowhere else then its a vacuum line. on my 2000 gmc safari ,there is a vacuum line that runs from the front of the engine compartment (left front} over to the left rear,usually right over the thermostat . when the hose break or gets a leak(very common, fix ed it every 2 years] the air/heat only comes out the defrost. it usually breaks right around the thermostat ,check there for a broken vacuum line. my mechanic fixed it good with a piece of heavy 5/16 inch hose.
  5. Wanabe check your blower motor resistor. When they go out, they only blow in one or two speeds. They are ususally located by or behind the blower motor. Cost only about 35bucks or so, and they are usually held im by 2 screws.
  6. below the heater fan under the hood look and see if you find a electrical connecter going to a small board mounted in the ductwork. It is a sensor of some sort. I had that problem on a Chevy van (1997) and that's what the problem was. Can't remember the part name, but I do remember it being a $20 part at AutoZone. The problem stemmed from a corroded connection. Had to go to a junk yard to get a new connector. GM garage couldn't even order it. Hope that helps!

    TomC was posting at the same time as me. The resistor he is talking about is the same thing I replaced. Make sure and check for corrosion at that plug or you'll replace it again within a couple of months
  7. thanks for all the replies, i will try them all. it really doe not bother me , but the wife bitches her feet are cold. thanks , i will update when i get it fixed
  8. check for a pen that may have fallen down the defrost vent and jamming up a door/.