Heater Control Inside, Air, Outside and Defroster Positions - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Rich72C10 · 11-04-2021, 09:15 AM

So, cool weather is upon us - YAY! So time to release the hot water, I have a manual water cut off valve to insure no hot water gets past that lovely vacuum control valve to the heater core for summer time :-)

But I have a question about how the top control lever works on a 4-season's system. When I go to Heater (middle row) and then Hot (bottom row) the Inside, Air, Outside and Defroster selector (top row) bounces to Air/Outside. If I try to take the lever to the Inside position, the middle/bottom bounce back closer to cold/AC (though not all the way).

So, when in Heater/Hot mode is putting the top row to "Inside" an invalid position?

Otherwise everything on my 4-seasons works. All the doors open/close when the levers are moved to their various positions. My control is a 2-port vacuum controller (not sure why some trucks have 3-port vacuum).

Rich72C10 · 11-04-2021, 09:30 AM

Nothing to see here, just an idiot that should have read his manual in his glove box first before posting.... RTFM Dude!

truckster · 11-04-2021, 12:28 PM

Unfortunately, I don't think you can run the AC compressor with the defrost like modern vehicles do.

Rich72C10 · 11-04-2021, 12:35 PM

I wasn't thinking this as A/C Air but as "Fresh Air" only. But I guess when the top lever is at Air and then all the way to the left it is "A/C" Compressor On?

**dmjlambert** · 11-06-2021, 01:14 AM

When the fan is on and the middle A/C-Heater lever is all the way to the left is when the compressor is powered on. I think that white line above the middle lever knob is where compressor is off, and any more to the left turns it on.

**Palf70Step** · 11-06-2021, 11:31 AM

That is about what I remember, but been a while. The compressors definitely did not work on defrost 87 and older.

11-04-2021, 09:15 AM	#1
Rich72C10 Mr. Cheyenne Join Date: Jun 2020 Location: Kyle, Texas Posts: 1,687	Heater Control Inside, Air, Outside and Defroster Positions So, cool weather is upon us - YAY! So time to release the hot water, I have a manual water cut off valve to insure no hot water gets past that lovely vacuum control valve to the heater core for summer time :-) But I have a question about how the top control lever works on a 4-season's system. When I go to Heater (middle row) and then Hot (bottom row) the Inside, Air, Outside and Defroster selector (top row) bounces to Air/Outside. If I try to take the lever to the Inside position, the middle/bottom bounce back closer to cold/AC (though not all the way). So, when in Heater/Hot mode is putting the top row to "Inside" an invalid position? Otherwise everything on my 4-seasons works. All the doors open/close when the levers are moved to their various positions. My control is a 2-port vacuum controller (not sure why some trucks have 3-port vacuum). Attached Images __________________ Richard *'72 Chevy C10 Cheyenne Super WHT/MED BRONZE/WHT SBC 350 \| TH350 \| LWB \| AC \| Buddy Seats Upgrades:** Tilt \| Front Sway Bar \| Radio \| Sliding Window \| Bed Spare w/Lock Bed Rails \| Full LEDs \| Courtesy Lights \| Tachometer \| Glovebox Lock & Light \| Head Light Relays \| *Upgraded Fully Super Trim

11-04-2021, 09:30 AM	#2
Rich72C10 Mr. Cheyenne Join Date: Jun 2020 Location: Kyle, Texas Posts: 1,687	Re: Heater Control Inside, Air, Outside and Defroster Positions Nothing to see here, just an idiot that should have read his manual in his glove box first before posting.... RTFM Dude! Attached Images __________________ Richard *'72 Chevy C10 Cheyenne Super WHT/MED BRONZE/WHT SBC 350 \| TH350 \| LWB \| AC \| Buddy Seats Upgrades:** Tilt \| Front Sway Bar \| Radio \| Sliding Window \| Bed Spare w/Lock Bed Rails \| Full LEDs \| Courtesy Lights \| Tachometer \| Glovebox Lock & Light \| Head Light Relays \| *Upgraded Fully Super Trim

11-04-2021, 12:28 PM	#3
truckster Registered User Join Date: Jan 2001 Location: Orem, Utah Posts: 7,982	Re: Heater Control Inside, Air, Outside and Defroster Positions Unfortunately, I don't think you can run the AC compressor with the defrost like modern vehicles do. __________________ I have sworn upon the altar of God, eternal hostility against every form of tyranny over the mind of man. - Thomas Jefferson

11-04-2021, 12:35 PM	#4
Rich72C10 Mr. Cheyenne Join Date: Jun 2020 Location: Kyle, Texas Posts: 1,687	Re: Heater Control Inside, Air, Outside and Defroster Positions I wasn't thinking this as A/C Air but as "Fresh Air" only. But I guess when the top lever is at Air and then all the way to the left it is "A/C" Compressor On? __________________ Richard *'72 Chevy C10 Cheyenne Super WHT/MED BRONZE/WHT SBC 350 \| TH350 \| LWB \| AC \| Buddy Seats Upgrades:** Tilt \| Front Sway Bar \| Radio \| Sliding Window \| Bed Spare w/Lock Bed Rails \| Full LEDs \| Courtesy Lights \| Tachometer \| Glovebox Lock & Light \| Head Light Relays \| *Upgraded Fully Super Trim

11-06-2021, 01:14 AM	#5
dmjlambert Senior Member Join Date: Apr 2016 Location: Cypress, TX Posts: 3,885	Re: Heater Control Inside, Air, Outside and Defroster Positions When the fan is on and the middle A/C-Heater lever is all the way to the left is when the compressor is powered on. I think that white line above the middle lever knob is where compressor is off, and any more to the left turns it on. Attached Images

11-06-2021, 11:31 AM	#6
Palf70Step State of Confusion! Join Date: Jul 2002 Location: Gulfport, MS USA Posts: 47,249	Re: Heater Control Inside, Air, Outside and Defroster Positions That is about what I remember, but been a while. The compressors definitely did not work on defrost 87 and older. __________________ Bill 1970 Chevy Custom/10 LWB Fleetside 2010 Toyota Tacoma PreRunner SR5 Double Cab - DD Member of Louisiana Classic Truck Club (LCTC) Bill's Gallery Life isn't tied with a bow, but it's still a gift. Live simply. Love generously. Care deeply. Speak kindly. Leave the rest to God!



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