How do I get the heat to defrost? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

rocking chevy · 11-28-2011, 07:22 PM

My dad has a 1970 c10 and the heat works, but he can't get it to defrost. Does anyone know how to switch it to defrost?

webfoot · 11-28-2011, 07:51 PM

If moving the lever results in no movement of the cable, either the round loop end of the cable has come off either end of the lever, on the control or on the box itself.

On mine the ducting was so shot that barely any air was getting up to the vents on the dash. Replacing the ducts made a marked improvement.

cdowns · 11-28-2011, 08:16 PM

there is a flapper dirvertor inside the box and it is a very common thing the breaks so air cant b routed to the defrosta

eightbanger · 11-28-2011, 08:18 PM

Quote:

Originally Posted by cdowns

there is a flapper dirvertor inside the box and it is a very common thing the breaks so air cant b routed to the defrosta

This on mine.

sjarrett71 · 11-28-2011, 08:35 PM

Are the defrost hoses connected and in one piece? They are bad for ripping and coming loose.

rocking chevy · 11-28-2011, 08:52 PM

where exactly is the flapper door, if the cable is broken we might be able to move it by hand.

hounddogs! · 11-28-2011, 11:25 PM

The arm that's front and center under the dash activates the defrost door. There's a good chance that the cable got stuck, then the lever broke when forced. You should have one hose (shown) that runs across, then up to the driver's side. The pass side goes straight up from the top of the box near where the cable is anchored.

rocking chevy · 11-29-2011, 11:45 AM

Thanks, that will help a lot.

68gmsee · 11-29-2011, 03:11 PM

If the truck is non a/c the defrost is not going to work very well. Newer a/c trucks rely on the moisture removing ability of the evaporater to defrost the windows.

Back in the old days before a/c about the only thing one could do is to wait until the truck warmed up to temp, turn the defroster on and let it idle until the heat dried the inside of the window. In Corpus Christi where I grew up, those old defrosters were almost worthless. We carried a lot of dry rags in the cars.

rocking chevy · 11-29-2011, 07:01 PM

it is a a/c pickup, but it doesn't work.

Southcity · 11-29-2011, 08:38 PM

If everything else already mentioned here checks out don't forget to make sure the fan works too as it makes a big difference in blowing the air out those Dash vents to help defrost.

11-28-2011, 07:22 PM	#1
rocking chevy Registered User Join Date: Apr 2011 Location: Nebraska Posts: 262	How do I get the heat to defrost? My dad has a 1970 c10 and the heat works, but he can't get it to defrost. Does anyone know how to switch it to defrost?

11-28-2011, 07:51 PM	#2
webfoot Registered User Join Date: Nov 2007 Location: Hermiston, OR Posts: 947	Re: How do I get the heat to defrost? If moving the lever results in no movement of the cable, either the round loop end of the cable has come off either end of the lever, on the control or on the box itself. On mine the ducting was so shot that barely any air was getting up to the vents on the dash. Replacing the ducts made a marked improvement. __________________ *Running in place gets you nowhere fast.* -me 1968 GTO 4-spd covnvertible 1970 K-20 4-speed, factory AC.

11-28-2011, 08:16 PM	#3
cdowns Senior Member Join Date: Jan 2003 Location: daytonabeach Posts: 22,956	Re: How do I get the heat to defrost? there is a flapper dirvertor inside the box and it is a very common thing the breaks so air cant b routed to the defrosta __________________ 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

11-28-2011, 08:35 PM	#5
sjarrett71 Registered User Join Date: Dec 2006 Location: Rolla, MO Posts: 2,463	Re: How do I get the heat to defrost? Are the defrost hoses connected and in one piece? They are bad for ripping and coming loose. __________________ -Scott-

11-28-2011, 08:52 PM	#6
rocking chevy Registered User Join Date: Apr 2011 Location: Nebraska Posts: 262	Re: How do I get the heat to defrost? where exactly is the flapper door, if the cable is broken we might be able to move it by hand.

11-28-2011, 11:25 PM	#7
hounddogs! Restoring it $200 at a time... Join Date: Aug 2008 Location: NE Kansas Posts: 886	Re: How do I get the heat to defrost? The arm that's front and center under the dash activates the defrost door. There's a good chance that the cable got stuck, then the lever broke when forced. You should have one hose (shown) that runs across, then up to the driver's side. The pass side goes straight up from the top of the box near where the cable is anchored. Attached Images __________________ Charter member of the 'Put the dimmer switch back on the damn floor where it belongs' Society '68 5.3L-4 speed LWB C20; grandpa bought it for the farm in '71. Now LS 5.3, rather than 327. DD '09 Pilot Weekender '65 Skylark 300-4V-4 speed Wife's '07 Lexus ES350; 117 actuator motors and I can't see the engine. Son's '04 F250 SuperCab 6.0

11-29-2011, 11:45 AM	#8
rocking chevy Registered User Join Date: Apr 2011 Location: Nebraska Posts: 262	Re: How do I get the heat to defrost? Thanks, that will help a lot.

11-29-2011, 03:11 PM	#9
68gmsee Active Member Join Date: Jul 2007 Location: Centrally located between Houston, Austin and Waco. BCS area. Posts: 7,947	Re: How do I get the heat to defrost? If the truck is non a/c the defrost is not going to work very well. Newer a/c trucks rely on the moisture removing ability of the evaporater to defrost the windows. Back in the old days before a/c about the only thing one could do is to wait until the truck warmed up to temp, turn the defroster on and let it idle until the heat dried the inside of the window. In Corpus Christi where I grew up, those old defrosters were almost worthless. We carried a lot of dry rags in the cars.

11-29-2011, 07:01 PM	#10
rocking chevy Registered User Join Date: Apr 2011 Location: Nebraska Posts: 262	Re: How do I get the heat to defrost? it is a a/c pickup, but it doesn't work.

11-29-2011, 08:38 PM	#11
Southcity Registered User Join Date: Aug 2007 Location: Redwood City, CA Posts: 1,177	Re: How do I get the heat to defrost? If everything else already mentioned here checks out don't forget to make sure the fan works too as it makes a big difference in blowing the air out those Dash vents to help defrost. __________________ 66 GMC Suburban Custom 66 Chevy K10 Suburban



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