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#1 |
Spanked once
![]() Join Date: Oct 2006
Location: Intheshop, Indiana
Posts: 969
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Factory AC and Heater help
It seems as if I have run into another little snag from my trucks previous life. In April I was going to swap out my engine for my new 383 and decided to re-do every thing up front from the ground up. My first clue that it had been wrecked once was the pass side fender was once white
![]() I have to patch where the fan motor seals , can't see it in the pic but it warped pretty bad and maybe cut in new metal in the corner where the most damage is if there isn't enough air flow. I am assuming both ac and heat recirculate the cab air? |
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#2 |
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Location: Intheshop, Indiana
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Re: Factory AC and Heater help
ttt
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#3 |
Senior Member
Join Date: Jul 2001
Location: Muskegon,MI,USA
Posts: 6,026
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Re: Factory AC and Heater help
My suggestion would be to fix the truck in the damaged areas. Sealing the flapper valve to prevent outside air from coming in is possible but not recommended. Sealing off the passenger side vent door will stop the air recirculation.
Jim
__________________
1971 Shortbox step side 4x4, 350 sbc, 3:07 rear end 1965 Impala SS 400 sbc, Muncie rock crusher 1966 Impala SS 396 bbc, TH 400 1969 El Camino, 350 sbc, TH 350 1971 Snowplow built on a Blazer frame 1972 GMC Short bed, stepside, TH 400, 427 BBC |
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#4 |
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Location: Intheshop, Indiana
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Re: Factory AC and Heater help
Got any reason for why it would not be recommended to seal the ac valve? Also I can't really tell where the fan gets it's supply. I can see the small steal ductwork that feeds but not the supply. Lmc calls the seal an AC shut off ??? Does that mean it has to have fresh air? Don't seem to efficient.
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#5 |
Senior Member
Join Date: Jul 2001
Location: Muskegon,MI,USA
Posts: 6,026
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Re: Factory AC and Heater help
The fan gets its air supply from the cowl area, (outside air) or the right side vent, (inside air). Blocking one or both will effectively stop your fan from blowing air.
The outside air is blocked by the closed flapper valve when the AC is on so that recirculated air is used. The flapper door is open when the heater is on so outside air is used. Here is the vacuum control schematic. Jim
__________________
1971 Shortbox step side 4x4, 350 sbc, 3:07 rear end 1965 Impala SS 400 sbc, Muncie rock crusher 1966 Impala SS 396 bbc, TH 400 1969 El Camino, 350 sbc, TH 350 1971 Snowplow built on a Blazer frame 1972 GMC Short bed, stepside, TH 400, 427 BBC |
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#6 |
Senior Member
![]() Join Date: Dec 2002
Location: Portland, Oregon
Posts: 901
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Re: Factory AC and Heater help
Previous owner of my truck had cut the refrigerant lines to the evaporator and removed the compressor and condenser. I used condenser, compressor, evaporator and hoses from a 1971 Pontiac. ( The parts were interchangeable. ) I also removed the outside air door and diaphragm and plugged the vacuum hose; leaving vacuum to the water valve as required. I also disconnected the recirculated (inside) air vacuum lines and sealed the door in closed position.
This ensured that all air to the heater/ air cond system was outside air. This simplification of the air intake system has worked out very satisfatory. I also mounted a toggle switch which turns compressor on/off; on the under lip of dash just below the air cond./ heater control assembly. This arrangement gives control to the system; heated, air cond or plain outside air thru the outlets; heater, air cond or defrost. Using outside air as a source for the system keeps a supply of fresh air in the cab at all times. If you or any of your passengers are smokers; keeping the cab interior with clean outside air is quite desirable, next to a necessity!........... Jim
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'71 GMC;fleetside;PB/PS/AC/CC/402 Eng./Custom Paint/110,000act miles/3 fuel tanks(52gal). Last edited by GMC Jim; 07-07-2007 at 07:00 AM. |
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#7 |
Senior Member
![]() Join Date: Dec 2002
Location: Portland, Oregon
Posts: 901
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Re: Factory AC and Heater help
I might add that the modifcation described above was done over 10 years ago; with no regrets..The vacuum lines are simplified...Vac source to vac reservoir, to control head vac switch. From the vac switch a line to water valve.
__________________
'71 GMC;fleetside;PB/PS/AC/CC/402 Eng./Custom Paint/110,000act miles/3 fuel tanks(52gal). |
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#8 | |
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Location: Intheshop, Indiana
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Re: Factory AC and Heater help
Quote:
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#9 |
Senior Member
![]() Join Date: Dec 2002
Location: Portland, Oregon
Posts: 901
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Re: Factory AC and Heater help
Richard H.---I disagree that blocking one or both will stop the fan from blowing air.... As I stated, my system uses outside air exclusively with no restriction.... Either inside air OR outside air can be used quite satisfactorily. As long as either outside air or inside air is used, the fan will operate normally.... Jim
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'71 GMC;fleetside;PB/PS/AC/CC/402 Eng./Custom Paint/110,000act miles/3 fuel tanks(52gal). |
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#10 |
Spanked once
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Location: Intheshop, Indiana
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Re: Factory AC and Heater help
GMC Jim ,sorry for not posting back yesterday You are both saying the same thing about the vents and I am going to hook it all up stock. Then I will find away to disable the outside air for my self and if there is a next owner he can have it his way. I will also come up with a way to run the ac pump while in defrost mode.
Thanks for your help RH |
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#11 |
Senior Member
![]() Join Date: Dec 2002
Location: Portland, Oregon
Posts: 901
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Re: Factory AC and Heater help
Rich, would be simple to disable the outside air door operation. As I recall the door is open except when vacuum is applied. If you would want the door to remain open; all your would have to do is to remove the vacuum line at the door and plug the hose. And if you want to control the compressor just mount a switch that is fed with 12 volts from the fuse panel and the other end of the wire to the compressor that controls the compressor clutch. You could then remove and tape the existing wire. This will then give you control of refrigerated air at any postion of the heater/air dash contols. Good luck to you on this, as you can see that the operation of the system is dependent upon how you select the vacuum to the design functions........Jim
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'71 GMC;fleetside;PB/PS/AC/CC/402 Eng./Custom Paint/110,000act miles/3 fuel tanks(52gal). Last edited by GMC Jim; 07-09-2007 at 09:15 PM. |
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#12 |
Registered User
Join Date: Jun 2007
Location: Kaufman TX
Posts: 160
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Re: Factory AC and Heater help
Someone messup the heater contols on my truck, I had to tyrap the heater control valve closed so the heater would not work. Where can i find a diagram on the heating and a/c system for a 70 swb.
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#13 |
Old member
Join Date: Jan 2002
Location: Liberty, & Garden City S.C. , U.S.
Posts: 19,936
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Re: Factory AC and Heater help
The A/C only works when the factory switch on the back side of the floor vent is activated by the cable pushing the switch in. This is where I hooked my fan motor wiring into also to turn the fan on when the compressor is activated. The fan is hooked to a relay but feed from here. Just remove the factory switch and add the toggle to the dash. I have been considering doing this but haven't gotten it done yet.
__________________
1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 ![]() Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs. |
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#14 |
Senior Member
![]() Join Date: Dec 2002
Location: Portland, Oregon
Posts: 901
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Re: Factory AC and Heater help
Andy, my previous msg states the advantage with the versitality and convenience of simply controling the A/C compressor with a switch. I mounted the switch on the dash lip just below the existing fan speed switch. The relay controls only the high speed fan; lower speeds are controlled by the resistor pack mounted in the top side of the plenum in the air distribution duct in the cab. 3 wires plug into this resistor pack; a 14 gauge yellow wire, a 14 gauge dark blue wire and a 16 gauge light blue wire. Hope this helps clarify the modification I have previously outlined.
Rickey, the GM "Truck Chassis Service Manual", contains the wiring diagram for the air conditioning system. If you don't have this manual, send me your address and I will mail you a copy of this diagram.......... Jim
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'71 GMC;fleetside;PB/PS/AC/CC/402 Eng./Custom Paint/110,000act miles/3 fuel tanks(52gal). Last edited by GMC Jim; 08-09-2007 at 03:12 AM. |
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#15 |
Old member
Join Date: Jan 2002
Location: Liberty, & Garden City S.C. , U.S.
Posts: 19,936
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Re: Factory AC and Heater help
GMC JIM, I have the shop manuals. I'm talking about the little push button switch on the back of the black box on the floor. The cable that runs from the dash right behind the duct work. If this switch isn't ingaged then the compressor will not run.
__________________
1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 ![]() Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs. |
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