Heat keeps blowing and blowing... - The 1947 - Present Chevrolet & GMC Truck Message Board Network

cwilkie · 05-27-2009, 03:41 PM

I have a question. The heat in my truck continues to blow when I am driving my truck. The fan is off and the heat arm closes off the door but the faster I drive the more heat comes out of the heater box. I thought it was the blower motor so I unplugged the power wire to it but the heat still blow. Could it be the heat resistor switch? I am pretty frustrated since it is starting to get warm out now. Does anyone have any ideas? Thanks.

Chance

UltraBlue71 · 05-27-2009, 04:35 PM

I've had trucks do that too, maybe not as bad as yours, pull the heater hoses and cap off the lines for the summer? Kinda Hokey, but I bet it would work...

6772owner · 05-27-2009, 04:41 PM

I believe that my truck did this when I first got it and my problem was the heater case was full of s**t and the door couldnt properly shut/seal out the air flow from the heater core. The cable might not be shutting the door properly due to adjustment/debris or it came unhooked from the door altogether?? Did this just "happen" or has it always done it? Hope this helps a little... all I know, someone else will chime in too.

69GMCLonghorn · 05-27-2009, 04:50 PM

There are 3 levers:
One for the defroster (not the problem)
2nd is for the amount of air coming in (middle lever). The other end of this one is inside the cab on the bottom of the heater box. Make sure this is fully closed.
3rd is the heat regulator. With mine, the cable keeps coming off the pin on the door. There's a small rubber boot that covers it up on the inside of the firewall (pass. side). Pull that boot out and make sure the cable is connected and that the door shuts.

As stated by 6772owner, there's probably an entire tree's worth of sh** in there. You may need to take a 12 pack and a Saturday afternoon and pull the heater assembly off the firewall and clean it out. You have to drop the inner fender well down to get to a couple bolts.

Oh and if you do this, plan on the truck being in pieces for a week, because you're going to see a thousand other things that you want to clean up, fix, paint, replace in the process.

HAVE FUN!

haulnrat · 05-27-2009, 05:44 PM

Instead of capping off the lines, put in a manual ball valve and close it for the summer.

**CPNE** · 05-27-2009, 08:36 PM

Quote:

Originally Posted by 6772owner

I believe that my truck did this when I first got it and my problem was the heater case was full of s**t and the door couldnt properly shut/seal out the air flow from the heater core. The cable might not be shutting the door properly due to adjustment/debris or it came unhooked from the door altogether?? Did this just "happen" or has it always done it? Hope this helps a little... all I know, someone else will chime in too.

...or the cable needs to be adjusted to close this door. I've seen this a few times

**leddzepp** · 05-27-2009, 09:04 PM

Quote:

Originally Posted by haulnrat

Instead of capping off the lines, put in a manual ball valve and close it for the summer.

Great idea

nicolas72gmc · 05-27-2009, 09:25 PM

x2. I did the ball valve thing on mine and it cools the cab just fine now. The heater and A/C were fighting each other.

gcburdic · 05-27-2009, 09:30 PM

where did you install the ball valve???...top or bottom hose??

nicolas72gmc · 05-27-2009, 10:10 PM

It is the bottom one. It is the 5/8 line that hooks into the front of the intake manifold. Originally it had the vacuum valve installed. Hope this helps.

**70C10Toejam** · 05-27-2009, 10:56 PM

I got a ball valve on both. 3/4 standard on upper, 3/4 PEX on lower. Not needed, but really nice when the heater core goes while at Menards. Shut 'er down and drive home.

6772owner · 05-28-2009, 08:57 AM

Of subject a little, but didnt only A/C trucks have the vacuum valve to shut off the heater core? My bro's 54' F100 has a cable actuated one that I have thought about adapting to mine, what you guys think?

69GMCLonghorn · 05-28-2009, 09:45 AM

Quote:

Originally Posted by 6772owner

Of subject a little, but didnt only A/C trucks have the vacuum valve to shut off the heater core? My bro's 54' F100 has a cable actuated one that I have thought about adapting to mine, what you guys think?

Honestly, these non-A/C heater systems are just not complicated. I would just fix it the way it should be. The ball valves are a good idea, but I wouldn't bother with a cable actuated one.

**leddzepp** · 05-28-2009, 09:51 AM

Quote:

Originally Posted by 6772owner

Of subject a little, but didnt only A/C trucks have the vacuum valve to shut off the heater core? My bro's 54' F100 has a cable actuated one that I have thought about adapting to mine, what you guys think?

You are correct. The vacuum valve shuts off the heater core when the A/C is on. The heater core sits right next to the A/C evaporator core, and this prevents the heater core from heating up and cancelling out the A/C.

6772owner · 05-28-2009, 10:24 AM

Ok thanks guys, I think that my trucks system works just fine now, just didnt know if I could cancel a little more heat transfer bypassing the heater core completely when not needed, I was going to rig the cable for the valve to the hot/cold selector on the control panel so that it worked in unison with the hot/cold selection (ie; slider on hot, coolant flows to core, and slider on cold, no flow) ???

05-27-2009, 03:41 PM	#1
cwilkie Chance Join Date: Sep 2001 Location: Belcourt ,ND, USA Posts: 750	Heat keeps blowing and blowing... I have a question. The heat in my truck continues to blow when I am driving my truck. The fan is off and the heat arm closes off the door but the faster I drive the more heat comes out of the heater box. I thought it was the blower motor so I unplugged the power wire to it but the heat still blow. Could it be the heat resistor switch? I am pretty frustrated since it is starting to get warm out now. Does anyone have any ideas? Thanks. Chance __________________ 1968 Chevrolet Stepside BB 396 w/TH400 1972 Chevrolet 3/4 Ton 4x4 BB 496 w/TH400 Last edited by cwilkie; 05-27-2009 at 03:41 PM.

05-27-2009, 04:35 PM	#2
UltraBlue71 Registered User Join Date: Feb 2009 Location: OKC OK Posts: 489	Re: Heat keeps blowing and blowing... I've had trucks do that too, maybe not as bad as yours, pull the heater hoses and cap off the lines for the summer? Kinda Hokey, but I bet it would work... __________________ "You can put lipstick on a pig, sure it's pretty pig, but it's still just a PIG... 71 LWB

05-27-2009, 04:41 PM	#3
6772owner Gearhead Join Date: Jan 2008 Location: Colorado Posts: 1,193	Re: Heat keeps blowing and blowing... I believe that my truck did this when I first got it and my problem was the heater case was full of s**t and the door couldnt properly shut/seal out the air flow from the heater core. The cable might not be shutting the door properly due to adjustment/debris or it came unhooked from the door altogether?? Did this just "happen" or has it always done it? Hope this helps a little... all I know, someone else will chime in too. __________________ 2002 Saturn SL2, My D/D 2019 Ford Fusion SE, Ecoboost - Wife's D/D 1993 Camaro Z28, A4, CAI, Cat-Back Exhaust Project C10 (my 72' C10 w/96' LT1, 700R4, bagged F&R, 18's (for now), Short/Fleet) -- SOLD! Build Thread: http://67-72chevytrucks.com/vboard/s...d.php?t=313644

05-27-2009, 04:50 PM	#4
69GMCLonghorn Registered User Join Date: Dec 2006 Location: Porter Ranch, CA Posts: 978	Re: Heat keeps blowing and blowing... There are 3 levers: One for the defroster (not the problem) 2nd is for the amount of air coming in (middle lever). The other end of this one is inside the cab on the bottom of the heater box. Make sure this is fully closed. 3rd is the heat regulator. With mine, the cable keeps coming off the pin on the door. There's a small rubber boot that covers it up on the inside of the firewall (pass. side). Pull that boot out and make sure the cable is connected and that the door shuts. As stated by 6772owner, there's probably an entire tree's worth of sh** in there. You may need to take a 12 pack and a Saturday afternoon and pull the heater assembly off the firewall and clean it out. You have to drop the inner fender well down to get to a couple bolts. Oh and if you do this, plan on the truck being in pieces for a week, because you're going to see a thousand other things that you want to clean up, fix, paint, replace in the process. HAVE FUN!

05-27-2009, 05:44 PM	#5
haulnrat Registered User Join Date: Oct 2005 Location: Iowa Posts: 136	Re: Heat keeps blowing and blowing... Instead of capping off the lines, put in a manual ball valve and close it for the summer.

05-27-2009, 09:25 PM	#8
nicolas72gmc Registered User Join Date: Aug 2008 Location: Sunny Arizona Posts: 525	Re: Heat keeps blowing and blowing... x2. I did the ball valve thing on mine and it cools the cab just fine now. The heater and A/C were fighting each other. __________________ Nick "Everyone has a plan, 'till they get punched in the mouth".........Mike Tyson 1968, GMC, SWB, Project 1972, GMC, LWB, Daily Driver, 383, headers, 2.5"/3" exhaust, 200r4, 3.5/5 ECE components. 1972, C/10, LWB, 350 vortec, th350

05-27-2009, 09:30 PM	#9
gcburdic Restoration Virgin! Join Date: Jan 2008 Location: Huntersville, NC Posts: 8,298	Re: Heat keeps blowing and blowing... where did you install the ball valve???...top or bottom hose?? __________________ Geoff with a G 1968 Chevy C10 SWB The Mistress 1972 Custom Deluxe C20 Suburban A Suburban Named Isabella 1966 Ford Mustang Mama's High School Graduation Present

05-27-2009, 10:10 PM	#10
nicolas72gmc Registered User Join Date: Aug 2008 Location: Sunny Arizona Posts: 525	Re: Heat keeps blowing and blowing... It is the bottom one. It is the 5/8 line that hooks into the front of the intake manifold. Originally it had the vacuum valve installed. Hope this helps. __________________ Nick "Everyone has a plan, 'till they get punched in the mouth".........Mike Tyson 1968, GMC, SWB, Project 1972, GMC, LWB, Daily Driver, 383, headers, 2.5"/3" exhaust, 200r4, 3.5/5 ECE components. 1972, C/10, LWB, 350 vortec, th350

05-27-2009, 10:56 PM	#11
70C10Toejam Hellasick Join Date: Jul 2006 Location: Death Moans, IA Posts: 876	Re: Heat keeps blowing and blowing... I got a ball valve on both. 3/4 standard on upper, 3/4 PEX on lower. Not needed, but really nice when the heater core goes while at Menards. Shut 'er down and drive home. __________________ I keep two MAGNUMS in my desk. One's a gun, and I keep it loaded. The other's a bottle and it keeps ME loaded. I'm Tracer Bullet. (Calvin and Hobbes) This life was a test. It was only a test. If this had been an actual life, you would have received instructions on where to go and what to do. RED meat is not bad for you...FUZZY BLUE/GREEN MEAT is bad for you!!!!!!!!!!!!! BUILT FORD TOUGH WITH CHEVY STUFF--sticker at Goodguys

05-28-2009, 08:57 AM	#12
6772owner Gearhead Join Date: Jan 2008 Location: Colorado Posts: 1,193	Re: Heat keeps blowing and blowing... Of subject a little, but didnt only A/C trucks have the vacuum valve to shut off the heater core? My bro's 54' F100 has a cable actuated one that I have thought about adapting to mine, what you guys think? __________________ 2002 Saturn SL2, My D/D 2019 Ford Fusion SE, Ecoboost - Wife's D/D 1993 Camaro Z28, A4, CAI, Cat-Back Exhaust Project C10 (my 72' C10 w/96' LT1, 700R4, bagged F&R, 18's (for now), Short/Fleet) -- SOLD! Build Thread: http://67-72chevytrucks.com/vboard/s...d.php?t=313644

05-28-2009, 10:24 AM	#15
6772owner Gearhead Join Date: Jan 2008 Location: Colorado Posts: 1,193	Re: Heat keeps blowing and blowing... Ok thanks guys, I think that my trucks system works just fine now, just didnt know if I could cancel a little more heat transfer bypassing the heater core completely when not needed, I was going to rig the cable for the valve to the hot/cold selector on the control panel so that it worked in unison with the hot/cold selection (ie; slider on hot, coolant flows to core, and slider on cold, no flow) ??? __________________ 2002 Saturn SL2, My D/D 2019 Ford Fusion SE, Ecoboost - Wife's D/D 1993 Camaro Z28, A4, CAI, Cat-Back Exhaust Project C10 (my 72' C10 w/96' LT1, 700R4, bagged F&R, 18's (for now), Short/Fleet) -- SOLD! Build Thread: http://67-72chevytrucks.com/vboard/s...d.php?t=313644 Last edited by 6772owner; 05-28-2009 at 10:24 AM. Reason: text



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