Help With Heater circuit

[gbfan100]

I have a 98 Blazer, and just recently started having problems with the Heater circuit. When I turn the selector to floor heat, the heat comes out the defrost. When I set it to defrost, i get that as well. Seems like all selections work, but the floor. Now when i drive to work my feet freeze. Not to mention it was 3 degrees out this week.

So Far I have removed lots of dash componets to ensure all the vaccum lines are connected and are functioning. I checked the one behind the glove box, and also 2 of them under the dash, by the gas pedal. They all seem to work and when I manually move them, I still do not get any air out of the lower vents (Floor)



Any ideas?

[Vermont7]

I have a 1998 Blazer that just started with this same problem 2 days ago. I need help as well!

[jmartin7]

Ditto!...turn the selector to floor, and air comes from the defrost...and not very hot. Changed the T-stat, and flushed the heater core to rule out those issues with the heating part of the problem, but not sure where to start looking for the floor/defrost problem. Please help...it's -2 degrees today, and more cold in the forecast.

Thanks in advance.

[76greg]

I have a 2001 Blazer with exact problem. All heater selections work except heat from floor. When heat from floor is selected I get defrost. I have tried all selections at all blower speeds. My feet are freezing now! Anyone have this fixed at a dealer?
I have a $100 deductable extended warranty and do not want to pay $100 to get this fixed. This is the only problem I have.
Thanks in advance! Greg

P.S. I saw a few other posts with similar problems of floor heat and defroster heat.

[jmartin7]

Got this link from Brokebyford at another forum (turn signal problems).

http://www.coolprofits.com/articles/...acuum_line.htm

Please post replies with success/failures, and/or followup advice. Thanks in advance.

[jmartin7]

Here's what happened this weekend on the 97 Blazer. This is Father-in-law's vehicle, and only get a chance on weekends to work on it...so I have all week to plan for next Saturday.

Read a bunch about accessing vacuum lines through glove box...not so on this vehicle. A few relays are accessible, but not vacuum lines. Partially disassembled dash, partially removed control panel for heat/cold selection, AC/floor/defrost/etc, selection, and fan speed selection...colored tubing bundle from back of AC/floor/defrost/etc. selector appeared to be in good shape...no cracked connectors or tubings, and nothing loose or disconnected. Reached in and moved tubing bundle to try to look for kinks/crimps in the tubings, and didn't see anything unusual.

Next partially disassembled lower part of air distribution ductwork, and reached in and manually moved the large damper accessible under the dash from driver's side. This damper moves up and down on its hinge point, and is rectangular shaped. Started engine to establish vacuum, selected floor, turned the blower on, and had so much air blowing at the floor I couldn't believe it. Reassembled everything, and now have plenty of air at the floor.

What did I fix? Not sure. Could've been a kinked/crimped tubing on the selector switch, or the damper I manually manipulated was stuck and I freed it up...or a combination of both.

Now I have air to the floor, but still not very hot...that's next. To recap previous work, changed T-stat and flushed heater core, with little change. Ideas are welcome.

Thanks in advance.

[gbfan100]

Originally Posted by gbfan100

I have a 98 Blazer, and just recently started having problems with the Heater circuit. When I turn the selector to floor heat, the heat comes out the defrost. When I set it to defrost, i get that as well. Seems like all selections work, but the floor. Now when i drive to work my feet freeze. Not to mention it was 3 degrees out this week.

So Far I have removed lots of dash componets to ensure all the vaccum lines are connected and are functioning. I checked the one behind the glove box, and also 2 of them under the dash, by the gas pedal. They all seem to work and when I manually move them, I still do not get any air out of the lower vents (Floor)



Any ideas?

I know this is old, but I have a work around.. It sounds stupid, but if you jam a wire into the heat duct right above the gad pedal, it will hold the flap open and you will get heat.. It seems there is a control valve in there and for some reason it no longer opens on its own.

[chewygoo1]

I had the identical problems on my 1995 S10 Blazer that you guys are experiencing. I endured this problem for sometime, until it got repaired unexpectedly. I took my truck in for some unrelated repairs and the mechanics took it upon themselves to fix the "duct" issue. It turned out to be a bad check valve somewhere in the vaccum lines that control the flaps in the duct work. They must have know exactly where to look, because I only got charged for the $5.00 check valve. The bad part is I didn't bother to ask where that check valve was. If you all want, I can pass by the shop in the next coupe of days.