What are these two things???
Thread Starter
Junior Member
Joined: Jul 2017
Posts: 33
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From: East Texas
Car: 89 RS LT1 Swap
Engine: LT1 5.7L
Transmission: 4L60E
What are these two things???
WTH are these two things? Are they vacuum related? I'm pretty sure it's emissions related but I'm stumped!
Joined: Sep 2005
Posts: 28,035
Likes: 2,501
Car: Yes
Engine: Usually
Transmission: Sometimes
Axle/Gears: Behind me somewhere
Re: What are these two things???
The one closer to the A/C accumulator is the AIR diverter valve, and is an emissions thing. The one behind the compressor is the heater control valve.
Thread Starter
Junior Member
Joined: Jul 2017
Posts: 33
Likes: 0
From: East Texas
Car: 89 RS LT1 Swap
Engine: LT1 5.7L
Transmission: 4L60E
Re: What are these two things???
Thanks man! Other than the little vacuum line running to the heater control, would either of these cause any vacuum loss issues?
Junior Member
Joined: Jan 2010
Posts: 53
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From: Wichita Falls Texas
Car: 1988 Trans Am GTA
Engine: 305 TPI
Transmission: T-5
Axle/Gears: 3.70
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Joined: Jun 2000
Posts: 5,364
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From: Enschede, Netherlands
Car: 82 TA 87 IZ L98 88 IZ LB9 88 IZ L98
Engine: 5.7TBI 5,7TPI 5.0TPI, 5,7TPI
Transmission: T5, 700R4, T5, 700R4
Axle/Gears: 3.08, 3.27, 3.45, 3.27
Re: What are these two things???
You would have cold air just not as cold as with a heater valve. The blend door regulates cold or hot air coming in. Plenty of cars came without a heater control valve... non ac ones and 82 83 (84?)
Last edited by Twin_Turbo; Sep 19, 2017 at 12:35 AM.
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Joined: May 2001
Posts: 702
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From: Houston TX
Car: 84 Z-28 Camaro, 2022 2500 silverado
Engine: 383
Transmission: T-56
Axle/Gears: richmond 3.73, eaton posi
Re: What are these two things???
All of my cars never had a heater control valve...2 84 z-28''s H engines and a G engine 84 tran am...AC worked great inall of them
Joined: Sep 2005
Posts: 28,035
Likes: 2,501
Car: Yes
Engine: Usually
Transmission: Sometimes
Axle/Gears: Behind me somewhere
Re: What are these two things???
Yup, my 83 as well; but, it worked noticeably better when I put a control head with that vacuum port, and a heater control valve, in it.
"It works great" is not the same thing as "it's as good as it can possibly be".
Which is not to say, you're wrong, in either case; only, that change and improvement, often only come in small increments. But over time and enough of those little increments, there can sometimes be VAST differences. For someone as old as me, who remembers throwing stuff at his lunch as it ran by to slow it down long enough to take a bite off of it before it had a chance to bite back, .... some of these things can be a bit amazing.
"It works great" is not the same thing as "it's as good as it can possibly be".
Which is not to say, you're wrong, in either case; only, that change and improvement, often only come in small increments. But over time and enough of those little increments, there can sometimes be VAST differences. For someone as old as me, who remembers throwing stuff at his lunch as it ran by to slow it down long enough to take a bite off of it before it had a chance to bite back, .... some of these things can be a bit amazing. 
