Heater control question? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

iufan71 · 06-29-2003, 04:52 PM

Took a little ride with the wifey today out around the town. The whole time,as has been since i have had the truck i could feel good heat coming out of the vents. The fan switch(the vertical switch) was all the way down,as well as both horizontal sliders were all the way to the left. Is this maybe an electrical problem with the control unit or a cable problem on the back of the unit? Just wanting some opinions before i try figuring out what my problem is. Thanks

77 Shortbed · 06-29-2003, 11:22 PM

I don't think it is electrical. It could be that the cable which opens or closes the door to the heater core is not closing all the way or the seal is shot allowing air past the door. There is a cable clamp on top of the ductwork behind the glovebox where the door can be adjusted.

But heat coming from the vents when the selection control is on off sounds like a vacumn problem. (I am assuming here that the truck originally came with A/C and the vents you are talking about are dash vents.)

Vacumn is used to move a door in the same ductwork that directs the air flow to the floor, defrost or vents. Once you have the glovebox out to check the heat cable start the truck and switch the selector from off to A/C, to vent, to heat, to defrost and watch the lever attached to the vacumn operated diaphram on top of the duct to see if it is moving. If it is not, you have a vacumn problem.

Start under the hood on the passenger side. There should be a vacuum canister or ball there, one side is connected to manifold vacuum and the other side is to the A/C master control panel. Check the hoses and plastic vacuum lines to and from the ball for cracks/breaks etc.

iufan71 · 06-30-2003, 12:41 AM

I see your in Central Indiana,where about? West side of Indianapolis here. And thanks for the info,definately going to check it out tommorrow. Been hoping to fix my a/c and get it all working as well. I know for sure one of the a/c hoses on the driver side more than likely has a hole in it,since it has duct tape all over it.

77 Shortbed · 06-30-2003, 01:03 AM

Southwest of Kokomo. Oh yeah, love my a/c. Just replaced everything except for the compressor last year.

apstguy · 07-01-2003, 03:31 PM

A little heat coming from the floor vent when everything is off is normal. Otherwise, you'll sufficate!

iufan71 · 07-01-2003, 05:09 PM

Moving the top horizontal switch with the iginition off,i hear something moving like a flapper behind the ashtray,but nothing behind the glovebox like shortbed77 was talking about

77 Shortbed · 07-01-2003, 08:10 PM

You're in the right area, just to the right of the ashtray and the left side of the glovebox. Does air come out of the floor, vent, and defroster when you change the upper selector to those positions?

iufan71 · 07-06-2003, 07:08 PM

Could you please post or give me a link to the cannister type thing you are refferring to under the hood on the passenger side?

iufan71 · 07-06-2003, 09:18 PM

Since when did GM use clear zip ties? I cut the zip tie,and amazingly my constant heat problem maybe gone.

iufan71 · 07-06-2003, 09:21 PM

Found the canister under the hood that shortbed77 was refferring to,and all vacuum is working fine into and out of there. Thanks for the help everyone

06-29-2003, 04:52 PM	#1
iufan71 Registered User Join Date: Apr 2003 Location: Indianapolis,IN Posts: 138	Heater control question? Took a little ride with the wifey today out around the town. The whole time,as has been since i have had the truck i could feel good heat coming out of the vents. The fan switch(the vertical switch) was all the way down,as well as both horizontal sliders were all the way to the left. Is this maybe an electrical problem with the control unit or a cable problem on the back of the unit? Just wanting some opinions before i try figuring out what my problem is. Thanks

06-30-2003, 12:41 AM	#3
iufan71 Registered User Join Date: Apr 2003 Location: Indianapolis,IN Posts: 138	77 Shortbed I see your in Central Indiana,where about? West side of Indianapolis here. And thanks for the info,definately going to check it out tommorrow. Been hoping to fix my a/c and get it all working as well. I know for sure one of the a/c hoses on the driver side more than likely has a hole in it,since it has duct tape all over it.

07-01-2003, 03:31 PM	#5
apstguy LED King Join Date: Jan 2003 Location: Sacramento, CA Posts: 2,087	A little heat coming from the floor vent when everything is off is normal. Otherwise, you'll sufficate! __________________ Tyler 1985 C10 305 w/ Bowtie OD TH700R4 3.42 LSD 202,000 miles 2006 Ford Focus ZX3 5-speed Stick 2016 Chevy Spark EV Gone: 2002.5 VW GTI 24v VR6 Gone: 2008 VW R32

07-01-2003, 05:09 PM	#6
iufan71 Registered User Join Date: Apr 2003 Location: Indianapolis,IN Posts: 138	Heater question Moving the top horizontal switch with the iginition off,i hear something moving like a flapper behind the ashtray,but nothing behind the glovebox like shortbed77 was talking about

07-06-2003, 07:08 PM	#8
iufan71 Registered User Join Date: Apr 2003 Location: Indianapolis,IN Posts: 138	77 Shortbed Could you please post or give me a link to the cannister type thing you are refferring to under the hood on the passenger side?

06-29-2003, 11:22 PM	#2
77 Shortbed Registered User Join Date: May 2003 Location: Central Indiana Posts: 16	I don't think it is electrical. It could be that the cable which opens or closes the door to the heater core is not closing all the way or the seal is shot allowing air past the door. There is a cable clamp on top of the ductwork behind the glovebox where the door can be adjusted. But heat coming from the vents when the selection control is on off sounds like a vacumn problem. (I am assuming here that the truck originally came with A/C and the vents you are talking about are dash vents.) Vacumn is used to move a door in the same ductwork that directs the air flow to the floor, defrost or vents. Once you have the glovebox out to check the heat cable start the truck and switch the selector from off to A/C, to vent, to heat, to defrost and watch the lever attached to the vacumn operated diaphram on top of the duct to see if it is moving. If it is not, you have a vacumn problem. Start under the hood on the passenger side. There should be a vacuum canister or ball there, one side is connected to manifold vacuum and the other side is to the A/C master control panel. Check the hoses and plastic vacuum lines to and from the ball for cracks/breaks etc.

06-30-2003, 01:03 AM	#4
77 Shortbed Registered User Join Date: May 2003 Location: Central Indiana Posts: 16	Southwest of Kokomo. Oh yeah, love my a/c. Just replaced everything except for the compressor last year.

07-01-2003, 08:10 PM	#7
77 Shortbed Registered User Join Date: May 2003 Location: Central Indiana Posts: 16	You're in the right area, just to the right of the ashtray and the left side of the glovebox. Does air come out of the floor, vent, and defroster when you change the upper selector to those positions?

07-06-2003, 09:18 PM	#9
iufan71 Registered User Join Date: Apr 2003 Location: Indianapolis,IN Posts: 138	Heating Problem maybe solved Since when did GM use clear zip ties? I cut the zip tie,and amazingly my constant heat problem maybe gone. Attached Images

07-06-2003, 09:21 PM	#10
iufan71 Registered User Join Date: Apr 2003 Location: Indianapolis,IN Posts: 138	Canister question Found the canister under the hood that shortbed77 was refferring to,and all vacuum is working fine into and out of there. Thanks for the help everyone



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