1986 Grand Am heater problem

Hey everybody, I'm having a problem with my Grand Am I'm hoping someone can help me with. It has the 3.0L V6. For some reason, the heater on this car won't work, when I turn the control nob to HTR it stops blowing air out of the vents. The A/C works fine though. Also, my cruise control doesn't work, someone told me that the heater problem and the cruise control problem might be linked. They said something about vacuum lines. Can anybody give me some advice on my problem? Thanks.

The heater not working could be due to a vaccuum line. First are you actually getting heat, just not from the lower "heater" vents? are you hearing a hissing noise come from the dash as you switch to the htr position? If you are hearing any type of hissing noise one of the vacuum lines probably came disconnected from the HVAC unit in the dash. If you are not getting any heat as well I would check into your heater core as well as your thermostat.... As for the cruise control, it's either the control switch has gone bad or the sensor on the trans, ( i believe it's a rubber diaphram) that has worn out, so it won't engage. Hope this helps some

I'm not getting any heat. Air only blows out of the vents by the floor too. Nothing comes out of the vents in the dash. I'm gonna try replacing the thermostat since it's cheap and I'm pretty sure this thermostat is about 10 years old. When I switch to the heater setting I just hear the usual vacuum sounds, not really any hissing. Air comes out of the proper vents on all the settings except for the heater setting. I also pulled out the HVAC unit, and made sure all the hoses were connected and in good shape. It just almost seems like there's a flap in there somewhere that closes off the airflow to the vents in the dash right when I switch to the heater.

Your thermostat probably is the cause for the no heat situation. You can definetly tell if the tempature gauge doesn't go up much, such as it sits around the 150 mark or less. You may still have a vaccuum leak causing the air not to go through the upper vents. I had a similar problem where i only could get upper vents and it was a disconnected vacuum hose. There is a possiblility that the vents maybe clogged, theres this foam stuff in the dash/vents the falls apart and gets stuck in the vents. so that could be a problem as well.... let me know how it goes.

oh yeah btw the thermostat on the 3.0 is in a little bit of an awkward spot.

Yeah, I already pulled out the old thermostat. The bolt closest to the radiator is really hard to get at, but other than that, it was pretty easy. The temperature guage is actually broken, so I'm not sure what temperature the car is running at. Is it hard to get to those air vents to see if there's a clog or if a flap isn't opening? On the A/C the air comes out strong out of all the vents like it should.. It's just the heater that has the problem.