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10-29-2011, 08:48 PM | #1 |
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Join Date: Sep 2010
Location: Kingston, PA
Posts: 394
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Heat issues
I have a few problems with my heat that I need to get straightened out. 1 I dont have any fan speed except high. 2 I cant use my defroster, and its snowing. 3 I ripped out one of the flaps int the main duct because I had to get it apart to change the core.
I know the fan speed is becuase of a resistor or something being bad, but I thought it was in the main duct and I didnt see it in there when I had it apart. Is that flap I ripped out the one that controls where the ait goes? It barely moved before so I didnt think it was that important and I needed to get it done. Im also missing the duct that goes to the vent on the far side of the dash on the drivers side if that matters. I have heat comeing from the vents on the dash and from the bottom, just not the top where I need it most.
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87 GMC Sierra 2500 4x4 350/TH350/NP203 Flow Tech long tube headers, throttle body spacer, Edelbrock Performer cam, true dual Flowmaster 40s, 6 inch Superlift suspension lift 2000 silverado extended cab stepside 5.3l. Stock for now |
10-29-2011, 08:54 PM | #2 |
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Location: Kingston, PA
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Re: Heat issues
Oh, and theres another flap that has a threaded metal rod on it that isnt hooked up to anything. What is that for and where should it go?
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87 GMC Sierra 2500 4x4 350/TH350/NP203 Flow Tech long tube headers, throttle body spacer, Edelbrock Performer cam, true dual Flowmaster 40s, 6 inch Superlift suspension lift 2000 silverado extended cab stepside 5.3l. Stock for now |
10-30-2011, 08:16 AM | #3 |
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Location: league city
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Re: Heat issues
you need to have vaccum to the ac controll head and this switches it from heat to de frost and such if you have vaccum then i would have to say you might need a new air box there are a few flaps in there if you find you need one i got a line on a good parts truck good luck
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10-30-2011, 12:22 PM | #4 |
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Re: Heat issues
There is at least one I know for a fact I need, the one I ripped out. The other ones all move but the one with the threaded rod isnt hooked up to anything and I cant find anywhere for it to go. Do you know what it should hook up to? If I get time today I will check the controls to make sure nothing came off, It doesnt sound like its trying to move anything when I change it from heat to defrost like it used to. Thanks
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87 GMC Sierra 2500 4x4 350/TH350/NP203 Flow Tech long tube headers, throttle body spacer, Edelbrock Performer cam, true dual Flowmaster 40s, 6 inch Superlift suspension lift 2000 silverado extended cab stepside 5.3l. Stock for now |
10-30-2011, 12:31 PM | #5 |
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Re: Heat issues
does it go to the floor on heater and vents on ac just not defrost
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10-30-2011, 12:42 PM | #6 |
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Location: Kingston, PA
Posts: 394
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Re: Heat issues
I took out all of the ac stuff so I didnt try that yet. I played with the switch a little with the heat, vent, and defrost but it always comes out of the front dash vents and the floor but not the defrost. Another thing I just realized, I just changed the motor in the truck and was having a hard time figuring out the vacuum lines. Where does the vacuum line for the heater hook up under the hood?
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87 GMC Sierra 2500 4x4 350/TH350/NP203 Flow Tech long tube headers, throttle body spacer, Edelbrock Performer cam, true dual Flowmaster 40s, 6 inch Superlift suspension lift 2000 silverado extended cab stepside 5.3l. Stock for now |
10-30-2011, 12:45 PM | #7 |
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Re: Heat issues
look for a big round black ball looking thing on the fire wall it needs to have a vaccum line to it and from there it goes into the cab of the truck to the ac controll panel and that is where the switching starts it goes from the controll pannel to different pods on the air box and that is where it changes from floor to vent to defrost hope this helps
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10-30-2011, 12:50 PM | #8 |
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Location: Kingston, PA
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Re: Heat issues
I know what you are talking about and im pretty sure theres nothing going to it and never was. I will take a look at it in a little bit. Where should the vacuum line that goes to it come from?
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87 GMC Sierra 2500 4x4 350/TH350/NP203 Flow Tech long tube headers, throttle body spacer, Edelbrock Performer cam, true dual Flowmaster 40s, 6 inch Superlift suspension lift 2000 silverado extended cab stepside 5.3l. Stock for now |
10-30-2011, 12:55 PM | #9 |
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Re: Heat issues
mine comes from a t behind the carb on the intake in front of the distributor
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10-30-2011, 03:06 PM | #10 |
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Location: Kingston, PA
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Re: Heat issues
The T used to be hooked up, but the ball wasnt and still isnt. I will check the T soon, im pretty sure I left it disconnected because I thought it was part of the old cruise control that I dont have anymore.
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87 GMC Sierra 2500 4x4 350/TH350/NP203 Flow Tech long tube headers, throttle body spacer, Edelbrock Performer cam, true dual Flowmaster 40s, 6 inch Superlift suspension lift 2000 silverado extended cab stepside 5.3l. Stock for now |
10-31-2011, 08:15 AM | #11 |
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Location: Kingston, PA
Posts: 394
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Re: Heat issues
I hooked up the T and now the defrost works some. I have the line from the back of the throttle body going to the T, and then the T goes to one of the sensors and the other part of it goes into the firewall. I dont have the ball hooked up but I have some defrost so im happy for now. There is still heat coming from the dash and floor with the defrost on.
Anyone know what the flap is for that has the threaded metal rod on it and where it hooks up to? thanks for the help so far.
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87 GMC Sierra 2500 4x4 350/TH350/NP203 Flow Tech long tube headers, throttle body spacer, Edelbrock Performer cam, true dual Flowmaster 40s, 6 inch Superlift suspension lift 2000 silverado extended cab stepside 5.3l. Stock for now |
10-31-2011, 10:25 AM | #12 |
78K & 79C Jimmys
Join Date: Nov 2009
Location: Ottawa Ont CANADA
Posts: 7,901
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Re: Heat issues
pics of my 88 may help
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John 1978 GMCJimmy4X4-350/203 1979 GMCJimmy4X2-305/350 |
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