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73-87 Chevy _ GMC Trucks => Interior & Equipment => Heating, Ventilation & Air Conditioning (HVAC) => Topic started by: rewardedgamer on September 06, 2013, 01:17:48 pm

Title: what is this?
Post by: rewardedgamer on September 06, 2013, 01:17:48 pm
ok so i was looking over my cab and i found this on the bottom in front of the door where you put your feet and have no idea what it is so if someone could help me that would be awesome... also its only on the passenger side

(http://i.imgur.com/5mE9BKp.jpg)
Title: Re: what is this?
Post by: 81_Chevy on September 06, 2013, 01:25:49 pm
its a vacuum canister hooked up with the A/C. when you flip your switch to A/C that opens up the vent behind it, since that's the intake for the system.
Title: Re: what is this?
Post by: rewardedgamer on September 06, 2013, 01:31:47 pm
ok thanks solved my curiosity
Title: Re: what is this?
Post by: pholliday1 on September 08, 2013, 08:49:39 pm
81 r u sure? I always thought that was just the vent control module( vacuum operated) and there is a return spring that needs to be hooked up can't tell from pict if its connected?
Title: Re: what is this?
Post by: bd on September 08, 2013, 09:37:46 pm
The image is of the recirulation door vacuum actuator.  The recirc door is paired with the plenum door located inside the cowl.  The recirc door is normally closed and the plenum door is normally open allowing the entry of outside air into the cab through the heater/evaporator housing.  When selecting "Max A/C," the plenum door closes and the recirc door opens to recirculate cabin air.

Edit:  door operation
Title: Re: what is this?
Post by: pedigo78 on September 08, 2013, 09:58:43 pm
is there an actual diagram for this system? I would like to see it
Title: Re: what is this?
Post by: bd on September 09, 2013, 09:15:37 am
is there an actual diagram for this system? I would like to see it

Look in the A/C & Heating section of the appropriate year 1973-87(91) GM Pickup Manuals (http://forum.73-87chevytrucks.com/smforum/index.php/topic,25639.msg213706.html#msg213706) in our Technical Pages.
Title: Re: what is this?
Post by: rewardedgamer on September 09, 2013, 02:58:33 pm
The image is of the recirulation door vacuum actuator.  The recirc door is paired with the plenum door located inside the cowl.  The recirc door is normally closed and the plenum door is normally open allowing the entry of outside air into the cab.  When selecting "Max A/C," the plenum door closes and the recirc door opens to recirculate cabin air.

Edit:  door operation
well my air conditioner isnt hooked up and i dont have Freon and that spring isnt hooked up so do i need to hook it up for heat tho?
Title: Re: what is this?
Post by: bd on September 09, 2013, 03:37:22 pm
The image is of the recirulation door vacuum actuator.  The recirc door is paired with the plenum door located inside the cowl.  The recirc door is normally closed and the plenum door is normally open allowing the entry of outside air into the cab.  When selecting "Max A/C," the plenum door closes and the recirc door opens to recirculate cabin air.
well my air conditioner isnt hooked up and i dont have Freon and that spring isnt hooked up so do i need to hook it up for heat tho?

Hook up the spring (or wire it closed) and leave the door in place or you'll have outside air blowing into the cab year round.  Could get mighty cold during the Winter.
Title: Re: what is this?
Post by: rewardedgamer on September 09, 2013, 04:41:48 pm
The image is of the recirulation door vacuum actuator.  The recirc door is paired with the plenum door located inside the cowl.  The recirc door is normally closed and the plenum door is normally open allowing the entry of outside air into the cab.  When selecting "Max A/C," the plenum door closes and the recirc door opens to recirculate cabin air.
well my air conditioner isnt hooked up and i dont have Freon and that spring isnt hooked up so do i need to hook it up for heat tho?

Hook up the spring (or wire it closed) and leave the door in place or you'll have outside air blowing into the cab year round.  Could get mighty cold during the Winter.
well i dont think air comes in the cab now when i have the windows shut and plus i dont feel air coming in the vents when im driving so maybe the guy before me wired it shut
Title: Re: what is this?
Post by: pholliday1 on September 10, 2013, 08:49:14 pm
Thanks for the clarity BD!