Defroster problem.. - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**1970cstblazer** · 10-11-2007, 01:24 PM

The defroster in my A/C equipped 1972 Cheyenne Super does not work well at all. On the defrost/deice setting, most of the air comes out of the dash vents. Very little air comes out of the defroster ducts. All of the hoses are in good condition. A cable moves a door right under the HVAC controls when I move the lever to defrost/deice. Any help is appreciated.

Andy4639 · 10-11-2007, 01:42 PM

When you move the cable back and forth does the flapper door inside shut. Those old flapper's were bad about coming undone inside the box. You need to take the heat peice that blows air out the bottom off and watch it while you move the controller to see if it's working. If the flapper doesn't flip up all the way with the air blowing then it's not feeding the air to the defrost hoses like it should.

**1970cstblazer** · 10-11-2007, 01:55 PM

Thanks. I will take a look at that and report back.

**1970cstblazer** · 10-13-2007, 06:47 PM

The defroster door is working properly. I lubed the cable and the door, adjusted it, and it now works better than it did.

However, the airflow at the defroster vents is still lackluster. I am still getting air at the A/C dash vents. Is there another cable that shuts off the air to the vents?

Andy4639 · 10-13-2007, 08:17 PM

The cable that you are moving is for the defrost. Check the one that turns the heat or A/C on and might have to adjust it also.

**1970cstblazer** · 10-14-2007, 07:19 PM

The plastic A/C / Heat blend door was broken around the steel shaft. I repaired the door, adjusted the cable, and the defroster works well now.

10-11-2007, 01:24 PM	#1
1970cstblazer All stock and staying that way Join Date: Jul 2003 Location: Elkland, PA Posts: 1,441	Defroster problem.. The defroster in my A/C equipped 1972 Cheyenne Super does not work well at all. On the defrost/deice setting, most of the air comes out of the dash vents. Very little air comes out of the defroster ducts. All of the hoses are in good condition. A cable moves a door right under the HVAC controls when I move the lever to defrost/deice. Any help is appreciated. __________________ 1970 K/5 Blazer CST 4WD, Bronze, 93k ACT. miles, 350, 4 speed, positraction, 16.5" x 8.25" wheel option, tilt, tach, vacuum, AM/FM, manual throttle...Dad ordered and purchased new 4/70. Currently frame off restoration in progress... 1972 Cheyenne Super 20 2WD, DK Blue/White, 90K ACT. miles, 402, TH400, 4.10 open, tilt, tach, vacuum, A/C, AM/FM, manual throttle.. A mostly original paint never rusted Texas survivor... 2017 Sierra 1500 SLT 4WD, Black, 41k miles, 5.3, 6L80E, 3.42 LS, 20" polished wheels, everything but moonroof and 6.2... 2019 Canyon SLT 4WD, White, 60k miles, 3.6, 8L45, 3.23 LS, 18" wheels

10-11-2007, 01:42 PM	#2
Andy4639 Old member Join Date: Jan 2002 Location: Liberty, & Garden City S.C. , U.S. Posts: 19,936	Re: Defroster problem.. When you move the cable back and forth does the flapper door inside shut. Those old flapper's were bad about coming undone inside the box. You need to take the heat peice that blows air out the bottom off and watch it while you move the controller to see if it's working. If the flapper doesn't flip up all the way with the air blowing then it's not feeding the air to the defrost hoses like it should. __________________ 1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.

10-11-2007, 01:55 PM	#3
1970cstblazer All stock and staying that way Join Date: Jul 2003 Location: Elkland, PA Posts: 1,441	Re: Defroster problem.. Thanks. I will take a look at that and report back. __________________ 1970 K/5 Blazer CST 4WD, Bronze, 93k ACT. miles, 350, 4 speed, positraction, 16.5" x 8.25" wheel option, tilt, tach, vacuum, AM/FM, manual throttle...Dad ordered and purchased new 4/70. Currently frame off restoration in progress... 1972 Cheyenne Super 20 2WD, DK Blue/White, 90K ACT. miles, 402, TH400, 4.10 open, tilt, tach, vacuum, A/C, AM/FM, manual throttle.. A mostly original paint never rusted Texas survivor... 2017 Sierra 1500 SLT 4WD, Black, 41k miles, 5.3, 6L80E, 3.42 LS, 20" polished wheels, everything but moonroof and 6.2... 2019 Canyon SLT 4WD, White, 60k miles, 3.6, 8L45, 3.23 LS, 18" wheels

10-13-2007, 06:47 PM	#4
1970cstblazer All stock and staying that way Join Date: Jul 2003 Location: Elkland, PA Posts: 1,441	Re: Defroster problem.. The defroster door is working properly. I lubed the cable and the door, adjusted it, and it now works better than it did. However, the airflow at the defroster vents is still lackluster. I am still getting air at the A/C dash vents. Is there another cable that shuts off the air to the vents? __________________ 1970 K/5 Blazer CST 4WD, Bronze, 93k ACT. miles, 350, 4 speed, positraction, 16.5" x 8.25" wheel option, tilt, tach, vacuum, AM/FM, manual throttle...Dad ordered and purchased new 4/70. Currently frame off restoration in progress... 1972 Cheyenne Super 20 2WD, DK Blue/White, 90K ACT. miles, 402, TH400, 4.10 open, tilt, tach, vacuum, A/C, AM/FM, manual throttle.. A mostly original paint never rusted Texas survivor... 2017 Sierra 1500 SLT 4WD, Black, 41k miles, 5.3, 6L80E, 3.42 LS, 20" polished wheels, everything but moonroof and 6.2... 2019 Canyon SLT 4WD, White, 60k miles, 3.6, 8L45, 3.23 LS, 18" wheels

10-13-2007, 08:17 PM	#5
Andy4639 Old member Join Date: Jan 2002 Location: Liberty, & Garden City S.C. , U.S. Posts: 19,936	Re: Defroster problem.. The cable that you are moving is for the defrost. Check the one that turns the heat or A/C on and might have to adjust it also. __________________ 1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.

10-14-2007, 07:19 PM	#6
1970cstblazer All stock and staying that way Join Date: Jul 2003 Location: Elkland, PA Posts: 1,441	Re: Defroster problem.. The plastic A/C / Heat blend door was broken around the steel shaft. I repaired the door, adjusted the cable, and the defroster works well now. __________________ 1970 K/5 Blazer CST 4WD, Bronze, 93k ACT. miles, 350, 4 speed, positraction, 16.5" x 8.25" wheel option, tilt, tach, vacuum, AM/FM, manual throttle...Dad ordered and purchased new 4/70. Currently frame off restoration in progress... 1972 Cheyenne Super 20 2WD, DK Blue/White, 90K ACT. miles, 402, TH400, 4.10 open, tilt, tach, vacuum, A/C, AM/FM, manual throttle.. A mostly original paint never rusted Texas survivor... 2017 Sierra 1500 SLT 4WD, Black, 41k miles, 5.3, 6L80E, 3.42 LS, 20" polished wheels, everything but moonroof and 6.2... 2019 Canyon SLT 4WD, White, 60k miles, 3.6, 8L45, 3.23 LS, 18" wheels



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