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

**Already Gone** · 07-28-2015, 11:29 AM

Today is the first day we have got any serious rain this summer. My truck is an original A/C truck with everything working. The slides on the HVAC control move freely from one side to the other and I had it set to defrost to keep my windows from steaming inside but that didn't work. Realizing the 72 has only 2 small ports for defrost to hit that big front window is the steaming normal on the trucks. Even with the fan on high I can blow harder ( and no, I'm not a blow hard ) than the air coming out of the ports.

**LockDoc** · 07-28-2015, 11:43 AM

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Are you sure that the control is actually opening the defrost door? Does the heater & A/C work good? Three possibilities that I can see, The defrost door is not opening, the heater boxes are full of debris or mouse nests, or the heater core is leaking. The leaking heater core will not cause lack of air flow but it will make your windshield steam up....

LockDoc

**Already Gone** · 07-28-2015, 11:48 AM

Heater core is good. It does take along time for the temp gauge to move up but the truck gets warm when up to temp. Is there doors on the heater boxes and is the defroster door visible form the cab. I have to fix this because i want to take this truck on the long haul Power Tour next year or the year after and I'm sure I'll be driving in the rain at some point.

**LockDoc** · 07-28-2015, 12:00 PM

Quote:

Originally Posted by Already Gone

Heater core is good. It does take along time for the temp gauge to move up but the truck gets warm when up to temp. Is there doors on the heater boxes and is the defroster door visible form the cab. I have to fix this because i want to take this truck on the long haul Power Tour next year or the year after and I'm sure I'll be driving in the rain at some point.

I am not that familiar with the A/C stuff but yes there would be a door or flapper to control the air to the defroster ducts and vents. Are you sure that the air ducts haven't come off of the heater outlets or the dash vents? That would be an easy check. (I think)..

LockDoc

PanelDeland · 07-28-2015, 12:04 PM

lo0ckDoc is right, the low hanging fruit is easiest to pick. Mine had the vent hoses rotted out. If the heater blows harder than the defrost, that is a good sign this is the problem. Mine's heat only but AC would do the same thing.

**Already Gone** · 07-28-2015, 12:08 PM

I never thought of the hoses. My last truck they were gooped and duct taped together. I'l start with the hoses. Maybe after 43 years they could be a little rotten.

cdowns · 07-28-2015, 03:02 PM

the flapper valve in the black box on the floor usually craps out causing poor air distribution

tommys72 · 07-28-2015, 04:46 PM

That valve was bad on mine, replaced it and got good defrost again

**Already Gone** · 07-28-2015, 05:17 PM

Thanks Tommy, That is why this site is so great everyone helping each other out. By the way, the P01's I got from you look great on the truck and I've had lots of compliments on them.

**Already Gone** · 08-04-2015, 09:31 PM

Quote:

Originally Posted by cdowns

the flapper valve in the black box on the floor usually craps out causing poor air distribution

Could you send a pic of the where the flapper valve is located because I see nothing that looks like door or valve in the front the heater box.

tommys72 · 08-04-2015, 11:05 PM

Quote:

Originally Posted by Already Gone

Could you send a pic of the where the flapper valve is located because I see nothing that looks like door or valve in the front the heater box.

I'll get a pic tomorrow. And I'm glad you're happy with the covers. I spent a lot of time on those. Tried to get them perfect

Andy4639 · 08-05-2015, 06:48 AM

This is the part that has the flapper inside it.

**Already Gone** · 08-05-2015, 10:15 AM

Thank you Andy.

tommys72 · 08-05-2015, 12:46 PM

There ya go, Andy beat me to it

**Already Gone** · 08-05-2015, 12:51 PM

Now to get it out of the truck. I get intimidated when I have to do stuff on the truck I haven't done before but it always seems too work out as long as I have enough time and take my time, and when its done and I've fixed the problem I always feel good. Working on my trucks over the years and accomplishing things has boosted my self confidence.

07-28-2015, 11:29 AM	#1
Already Gone 70+ ( Old Skool Club ) Join Date: Nov 2003 Location: Saskatoon, Saskatchewan ,Canada Posts: 9,105	Defroster Question Today is the first day we have got any serious rain this summer. My truck is an original A/C truck with everything working. The slides on the HVAC control move freely from one side to the other and I had it set to defrost to keep my windows from steaming inside but that didn't work. Realizing the 72 has only 2 small ports for defrost to hit that big front window is the steaming normal on the trucks. Even with the fan on high I can blow harder ( and no, I'm not a blow hard ) than the air coming out of the ports. __________________ 1972 C10 Custom/Deluxe 613 Highlander 406/700R4 1999 White Tahoe LS 4x2 with Z56 Police Package 1992 K1500 GMC Suburban Members I have personally met: MusicMan70 - HeavyD - ChewyChevy67 - StingRay -71SWB4x4 - 67 Burb - DeadheadNM - too much stuff - bc65 - das601 " Circumsatances Do Not Change Responsibility " " The Sky is not the Limit, Your Mind is." Marilyn Monroe .. RIP Charlie Watts 1941 - 2021

07-28-2015, 11:43 AM	#2
LockDoc The Older Generation Join Date: Aug 2006 Location: Montezuma, Iowa Posts: 25,393	Re: Defroster Question - Are you sure that the control is actually opening the defrost door? Does the heater & A/C work good? Three possibilities that I can see, The defrost door is not opening, the heater boxes are full of debris or mouse nests, or the heater core is leaking. The leaking heater core will not cause lack of air flow but it will make your windshield steam up.... LockDoc __________________ Leon Locksmith, Specializing In Antique Trucks, Automobiles, & Motorcycles (My Dually Pickup Project Thread) http://67-72chevytrucks.com/vboard/s...d.php?t=829820 -

07-28-2015, 11:48 AM	#3
Already Gone 70+ ( Old Skool Club ) Join Date: Nov 2003 Location: Saskatoon, Saskatchewan ,Canada Posts: 9,105	Re: Defroster Question Heater core is good. It does take along time for the temp gauge to move up but the truck gets warm when up to temp. Is there doors on the heater boxes and is the defroster door visible form the cab. I have to fix this because i want to take this truck on the long haul Power Tour next year or the year after and I'm sure I'll be driving in the rain at some point. __________________ 1972 C10 Custom/Deluxe 613 Highlander 406/700R4 1999 White Tahoe LS 4x2 with Z56 Police Package 1992 K1500 GMC Suburban Members I have personally met: MusicMan70 - HeavyD - ChewyChevy67 - StingRay -71SWB4x4 - 67 Burb - DeadheadNM - too much stuff - bc65 - das601 " Circumsatances Do Not Change Responsibility " " The Sky is not the Limit, Your Mind is." Marilyn Monroe .. RIP Charlie Watts 1941 - 2021

07-28-2015, 12:04 PM	#5
PanelDeland I am a Referee of life. Join Date: Jun 2000 Location: Greensboro N.C. Posts: 13,993	Re: Defroster Question lo0ckDoc is right, the low hanging fruit is easiest to pick. Mine had the vent hoses rotted out. If the heater blows harder than the defrost, that is a good sign this is the problem. Mine's heat only but AC would do the same thing. __________________ The 47-present Chevrolet and GMC Truck Message Board Network,it's owners,moderators,members,and associates of any type should not be held responsible for my opinion. You can't fix stupid,not even with duct tape. "My appearance is due to the fact that "GOD" does punish you for having too much fun!" Barrett-Jackson has perfected alchemy,they make rust into gold! "You can lead a horse to water but you can't saddle a duck" "Cleverly disguised as a 'Responsible Adult' "Sometimes your Knight in shining armor is just a retard in tinfoil"

07-28-2015, 12:08 PM	#6
Already Gone 70+ ( Old Skool Club ) Join Date: Nov 2003 Location: Saskatoon, Saskatchewan ,Canada Posts: 9,105	Re: Defroster Question I never thought of the hoses. My last truck they were gooped and duct taped together. I'l start with the hoses. Maybe after 43 years they could be a little rotten. __________________ 1972 C10 Custom/Deluxe 613 Highlander 406/700R4 1999 White Tahoe LS 4x2 with Z56 Police Package 1992 K1500 GMC Suburban Members I have personally met: MusicMan70 - HeavyD - ChewyChevy67 - StingRay -71SWB4x4 - 67 Burb - DeadheadNM - too much stuff - bc65 - das601 " Circumsatances Do Not Change Responsibility " " The Sky is not the Limit, Your Mind is." Marilyn Monroe .. RIP Charlie Watts 1941 - 2021

07-28-2015, 03:02 PM	#7
cdowns Senior Member Join Date: Jan 2003 Location: daytonabeach Posts: 22,956	Re: Defroster Question the flapper valve in the black box on the floor usually craps out causing poor air distribution __________________ 71c-10 350/2004r/4:11 lowered3/4 longbed/dead by hurricane MEANING OF DEATH::::: SOMEBODY ELSE GETS YOUR STUFF DONT BELIEVE EVERYTHING YOU THINK TAKE MY ADVISE;I DON'T USE IT ANYWAY

07-28-2015, 04:46 PM	#8
tommys72 Registered User Join Date: Jun 2012 Location: springfield mo Posts: 3,075	Re: Defroster Question That valve was bad on mine, replaced it and got good defrost again __________________ United States Marine Corps 2000-2011 Iraq and Afghanistan veteran Just living life now and enjoying it and my wife, daughter and son

07-28-2015, 05:17 PM	#9
Already Gone 70+ ( Old Skool Club ) Join Date: Nov 2003 Location: Saskatoon, Saskatchewan ,Canada Posts: 9,105	Re: Defroster Question Thanks Tommy, That is why this site is so great everyone helping each other out. By the way, the P01's I got from you look great on the truck and I've had lots of compliments on them. __________________ 1972 C10 Custom/Deluxe 613 Highlander 406/700R4 1999 White Tahoe LS 4x2 with Z56 Police Package 1992 K1500 GMC Suburban Members I have personally met: MusicMan70 - HeavyD - ChewyChevy67 - StingRay -71SWB4x4 - 67 Burb - DeadheadNM - too much stuff - bc65 - das601 " Circumsatances Do Not Change Responsibility " " The Sky is not the Limit, Your Mind is." Marilyn Monroe .. RIP Charlie Watts 1941 - 2021

08-05-2015, 06:48 AM	#12
Andy4639 Old member Join Date: Jan 2002 Location: Liberty, & Garden City S.C. , U.S. Posts: 19,936	Re: Defroster Question This is the part that has the flapper inside it. __________________ 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.

08-05-2015, 10:15 AM	#13
Already Gone 70+ ( Old Skool Club ) Join Date: Nov 2003 Location: Saskatoon, Saskatchewan ,Canada Posts: 9,105	Re: Defroster Question Thank you Andy. __________________ 1972 C10 Custom/Deluxe 613 Highlander 406/700R4 1999 White Tahoe LS 4x2 with Z56 Police Package 1992 K1500 GMC Suburban Members I have personally met: MusicMan70 - HeavyD - ChewyChevy67 - StingRay -71SWB4x4 - 67 Burb - DeadheadNM - too much stuff - bc65 - das601 " Circumsatances Do Not Change Responsibility " " The Sky is not the Limit, Your Mind is." Marilyn Monroe .. RIP Charlie Watts 1941 - 2021

08-05-2015, 12:46 PM	#14
tommys72 Registered User Join Date: Jun 2012 Location: springfield mo Posts: 3,075	Re: Defroster Question There ya go, Andy beat me to it __________________ United States Marine Corps 2000-2011 Iraq and Afghanistan veteran Just living life now and enjoying it and my wife, daughter and son

08-05-2015, 12:51 PM	#15
Already Gone 70+ ( Old Skool Club ) Join Date: Nov 2003 Location: Saskatoon, Saskatchewan ,Canada Posts: 9,105	Re: Defroster Question Now to get it out of the truck. I get intimidated when I have to do stuff on the truck I haven't done before but it always seems too work out as long as I have enough time and take my time, and when its done and I've fixed the problem I always feel good. Working on my trucks over the years and accomplishing things has boosted my self confidence. __________________ 1972 C10 Custom/Deluxe 613 Highlander 406/700R4 1999 White Tahoe LS 4x2 with Z56 Police Package 1992 K1500 GMC Suburban Members I have personally met: MusicMan70 - HeavyD - ChewyChevy67 - StingRay -71SWB4x4 - 67 Burb - DeadheadNM - too much stuff - bc65 - das601 " Circumsatances Do Not Change Responsibility " " The Sky is not the Limit, Your Mind is." Marilyn Monroe .. RIP Charlie Watts 1941 - 2021



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