heater control - The 1947 - Present Chevrolet & GMC Truck Message Board Network

hotrodhomi · 10-27-2004, 09:39 AM

My A/c and Heat vent control is stuck or something. The air only blows out from the floor. I looked under the dash and when I slide the selector lever back and forth I can feel the cable move. My question is, do I need to take out the whole vent assembly from under my dash to see if the air directing flap moves or not?

Jonboy · 10-27-2004, 10:21 AM

What year is your truck? I think the vent control is vacuum operated, and the temp is cable operated. If it is vacuum, there is a switch with 7 ports on it ( I think there is 7) that has a tendency to go bad. It will be on the A/C control head.

cochino12 · 10-27-2004, 10:34 AM

try this

hotrodhomi · 10-27-2004, 02:32 PM

As far as I can tell, there's actually 3 doors-

1. On the passenger side wall below the glove box. I imagine it's the door that allows cool(not air-conditioned) air into the cab when the heat control is set on cool.

2. Below the left bottom corner of the glove box. This is door I'm talking about. It diverts hot/air conditioned air between the vents or the defrost/heater. This is the door that had the broken clip.

3. Below the ashtray. This is yet another diverter that sends the air either to the floor or the defrost vents.

Keep in mind that all these doors are hidden by the black air tubing and can't be accessed unless the tubing is removed. I also had to take my glovebox door off.

Using the numbering above, I'll try to explain what I think happens when you switch your heater control around. I'll ignore the cool setting because most of the problems I've read about occur when people are using their heater:

Door #2 normally sits open. This allows the air to travel through to the vents. When you slide your control switch over to defrost, door #2 closes and the air is forced into a different set of plastic tubing that feeds both the defrost and floor vents. If you slide the heater switch to floor, door #3 closes and shuts off the flow to the defrost and diverts it to the floor. Does that make sense?

So basically you've got a couple different doors that work in conjunction with eachother. There's actually another door that controls how much heat gets through to door #2 but I think this post is confusing enough already!!!!

One other thing: my 84 has A/C, and the doors/diverters I'm referring to are vacuum operated. I'm not sure if a truck without A/C is setup the same way.

I hope I'm not explaining this incorrectly. If I am, somebody please step in and straighten me out. Up until yesterday I wasn't sure how everything worked myself.
good stuff. That should help. thanks,
HRH

10-27-2004, 09:39 AM	#1
hotrodhomi Registered User Join Date: Apr 2004 Location: Sacramento Posts: 3,737	heater control My A/c and Heat vent control is stuck or something. The air only blows out from the floor. I looked under the dash and when I slide the selector lever back and forth I can feel the cable move. My question is, do I need to take out the whole vent assembly from under my dash to see if the air directing flap moves or not?

10-27-2004, 10:21 AM	#2
Jonboy Slots go on anything! Join Date: May 2003 Location: Richardson, TX Posts: 5,957	What year is your truck? I think the vent control is vacuum operated, and the temp is cable operated. If it is vacuum, there is a switch with 7 ports on it ( I think there is 7) that has a tendency to go bad. It will be on the A/C control head. __________________ 1974 Jimmy- 5.3/4L80e/NP241

10-27-2004, 10:34 AM	#3
cochino12 It followed me home? Join Date: Mar 2003 Location: Yup Posts: 5,751	try this __________________ Adam That's why they call it a shortcut Kyle, if it was easy it would just be the way. 86 c-10 SWB 85 CCSB 90 GMC K30 Crew SRW 1985 C30 Dually

10-27-2004, 02:32 PM	#4
hotrodhomi Registered User Join Date: Apr 2004 Location: Sacramento Posts: 3,737	As far as I can tell, there's actually 3 doors- 1. On the passenger side wall below the glove box. I imagine it's the door that allows cool(not air-conditioned) air into the cab when the heat control is set on cool. 2. Below the left bottom corner of the glove box. This is door I'm talking about. It diverts hot/air conditioned air between the vents or the defrost/heater. This is the door that had the broken clip. 3. Below the ashtray. This is yet another diverter that sends the air either to the floor or the defrost vents. Keep in mind that all these doors are hidden by the black air tubing and can't be accessed unless the tubing is removed. I also had to take my glovebox door off. Using the numbering above, I'll try to explain what I think happens when you switch your heater control around. I'll ignore the cool setting because most of the problems I've read about occur when people are using their heater: Door #2 normally sits open. This allows the air to travel through to the vents. When you slide your control switch over to defrost, door #2 closes and the air is forced into a different set of plastic tubing that feeds both the defrost and floor vents. If you slide the heater switch to floor, door #3 closes and shuts off the flow to the defrost and diverts it to the floor. Does that make sense? So basically you've got a couple different doors that work in conjunction with eachother. There's actually another door that controls how much heat gets through to door #2 but I think this post is confusing enough already!!!! One other thing: my 84 has A/C, and the doors/diverters I'm referring to are vacuum operated. I'm not sure if a truck without A/C is setup the same way. I hope I'm not explaining this incorrectly. If I am, somebody please step in and straighten me out. Up until yesterday I wasn't sure how everything worked myself. good stuff. That should help. thanks, HRH



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