Heater/AC switch only blows through defrost

Hi,

This is my first post. I just bought a '97 Astro van and a month after the switch that controls whether the fan blows through the vent/floor/defrost stopped working. Regardless of the setting it is on, it always blows through the defrost vent.

Winters coming on so I figure I better get it fixed. Any help diagnosing the problem and possible solutions is appreciated.

Chad.

hi, check the vac source line from the engine to the vacuum check valve. this line runs along the front of the engine right by the thermostat housing, it is a plastic line and usually breaks right by the thermostat housing due to the heat. the heat causes the line to get brittle and break. Just replace line with a piece of vacuum hose, this should get your hvac system back up and switching modes again.
good luck

I have this same problem with my 2001 Astro AWD....I found the broken vacuum line, however, I'm having trouble getting the "doghouse " off, any suggestions or is there an easy way to remove?

Thanks

I just removed doghouse on my 99. theres two nuts and two bolts on the bottom of house that need to come off. there is a strip of carpet that covers them up. it's velcroed so it is easy to remove. they are 9/16" then pop off the two decorative caps on the sides and remove the two star pattern bolts. then pull off the center console. then there are two 5/8" bolts way in the back of house securing it to the firewall. you'll need a really long extension on your ratchet. then doghouse should pull right off. you'll have to twist and maneuver the dog house to get it past the seats to get it out of the way.

I am an owner of a 1998 Chevy Astro with rear heat and rear air. My problem was only cold air out of the rear heat and only the defrost vents worked in the front only. I will try to be as detailed as possible. Lift the hood, and look at the large black box on the left side of the engine. Just behind the AC reservoir, there is a vacuum line attached to the large black box, that looks like a Tee fitting with three connections. One went to the float switch, the other goes straight down to the vacuum ball located on the frame of the vehicle (underneath). The last is a thin vacuum line that looks like an electrical wire. Pull on all three lines one at a time. If one pulls all the way up to you, that is the broken one. The thin wire was broken in half on my Astro. The fix was to remove the air filter tube (the three inch flex tube that goes to the air filter box). Once removed, look for a flexible black tubing about a 1/2 inch round that should look empty because your line is broken. Pull the tubing to reveal the other half of the hose and reconnect with tubing that will fit over the thin blak wire. Not sure what size, but what I did notice is that this was probably the same problem that GM fixed before when the vehicle was under warranty because my line looked repaired but was broken in a different spot. Before I reinstalled the air box tubing, I did wrap the entire line with aluminum foil. I am not a professional, but I tried this and it worked for me. Good luck. This feels like the scene in Independence Day when they figured out how to bring down the spaceships in the sky. Good luck.

i looked the place you guys told me and found the vac line broke this forum is cool thx alot to you guys

hi, check the vac source line from the engine to the vacuum check valve. this line runs along the front of the engine right by the thermostat housing, it is a plastic line and usually breaks right by the thermostat housing due to the heat. the heat causes the line to get brittle and break. Just replace line with a piece of vacuum hose, this should get your hvac system back up and switching modes again.
good luck
I was having this same problem. knew it was a vacuum line, but where to look? It was right where you said it was. I used a new piece of hose about a foot long with an inside diameter that would slip over original hose. Slipped it on and rerouted it away from the thermostat area and it worked . Didn't even have to take off the engine cover. Extra lenght of new hose seams to seal the vacuum very good.... Should work until I get into the engine compartment again and can fix it right.........Thanks!!!!

I have a 2002 astor cargo van.The air conditioner/heater switch blows air a little bit more each time i ratchet it up.The problem is it does not come out fast enough.Is this the blower motor?If so,where is it located.Is it easy to replace?i