Thermo vacuum switch - Pontiac GTO Forum
User Tag List

Reply
 
LinkBack Thread Tools Display Modes
post #1 of 12 (permalink) Old 02-05-2018, 02:30 PM Thread Starter
 
Join Date: Jan 2017
Posts: 166
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 36 Post(s)
Thermo vacuum switch

Hi everyone. My '71 GTO came with factory a/c. When I first bought the car, some pieces were missing and since then, I've been buying parts to put it back together. A missing piece is the thermo vacuum switch that screws into the passenger side intake. I've researched this part and I see it is offered in a 5 port and 3 port variety. I do believe I would need the 5 port. Would that be correct?? I've also checked the schematics in my repair and assembly manuals, but can't seem to locate where this switch gets it's vacuum from. Would anyone know that?? Thank you very much.
Nicholas is offline  
Sponsored Links
Advertisement
 
post #2 of 12 (permalink) Old 02-05-2018, 07:32 PM
 
Join Date: Jan 2015
Location: Injun Territory, 'Merica!
Posts: 1,611
Mentioned: 0 Post(s)
Tagged: 1 Thread(s)
Quoted: 121 Post(s)
For '71 only 455 HO equipped cars used the thermostatic switch with rubber stob & 3 vac lines. D-port cars used the three prong thermostatic switch, which '71 HO cars also used on drivers side water crossover outlet when equipped with factory AC.
Pinion head is offline  
post #3 of 12 (permalink) Old 02-05-2018, 07:38 PM
 
integrity6987's Avatar
 
Join Date: May 2017
Location: NW Ohio
Posts: 151
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 46 Post(s)
Garage
vacuum is essentially any pressure lower than atmospheric pressure. Like when you suck soda from a cup. The source of vacuum is as you stated - the intake manifold. under low engine load a vacuum is created by the open intake valves and downward travel of the pistons on the intake stroke.

DK

<)))>><

"Pray as though everything depended on God. Work as though everything depended on you." - Saint Augustine
integrity6987 is offline  
 
post #4 of 12 (permalink) Old 02-05-2018, 08:22 PM
 
Join Date: Jul 2017
Location: Winona, MN
Posts: 174
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 33 Post(s)
Correct me if I'm wrong. But, the aforementioned switch is actually vacuum operated by the temperature of the water that opens the switch for vacuum. I believe it is mostly for emissions purposes and gets ported to the charcoal canister for one. Therefor, I have to ask if it's even necessary to install if one isn't using a charcoal canister?
tjs72goat is offline  
post #5 of 12 (permalink) Old 02-05-2018, 08:44 PM Thread Starter
 
Join Date: Jan 2017
Posts: 166
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 36 Post(s)
Quote:
Originally Posted by tjs72goat View Post
Correct me if I'm wrong. But, the aforementioned switch is actually vacuum operated by the temperature of the water that opens the switch for vacuum. I believe it is mostly for emissions purposes and gets ported to the charcoal canister for one. Therefor, I have to ask if it's even necessary to install if one isn't using a charcoal canister?
I'm trying to put my factory a/c back together, but I really don't know exactly what it looks like, because it came missing parts. Already, I have a deficit. I've looked in my repair/assembly manuals and can't find a good schematic of mainly electrical and vacuum that pertains to operating the a/c. Also looked on line and can't find anything definitive. I inquired about this thermos vacuum switch, because I thought it was part of the a/c. I just read where it's not. Has more to do with the charcoal filter, which I'm not using, the carb. and distributor. Basically emissions. Nothing mentioned about the a/c. So, that is my mistake. This is something that I won't be needing. I'm guessing that the a/c is basically electrical and the rest of the system, heat and defroster, allows the air via doors into the driver compartment, The doors are operated by vacuum from the dash switch. That's where my problem lies. Where the lines go, their origin, source, etc.?? I'd like to have something to look at, but don't know where to find it. Thank you for the responses.
Nicholas is offline  
post #6 of 12 (permalink) Old 02-05-2018, 09:59 PM
 
Join Date: Jan 2015
Location: Injun Territory, 'Merica!
Posts: 1,611
Mentioned: 0 Post(s)
Tagged: 1 Thread(s)
Quoted: 121 Post(s)
Quote:
Originally Posted by tjs72goat View Post
Correct me if I'm wrong. But, the aforementioned switch is actually vacuum operated by the temperature of the water that opens the switch for vacuum. I believe it is mostly for emissions purposes and gets ported to the charcoal canister for one. Therefor, I have to ask if it's even necessary to install if one isn't using a charcoal canister?
The thermostatic valve you are thinking of is the '72 PURGE valve. Own three '72's, all use that valve. '71's, like mentioned before, only use the 5 port thermostatically controlled Vac style switch on 455 HO cars. Though 5 ports on the switch, only 3 are used. The stob and three hose set-up feeds vacuum to the distributor. This thermostatic vac switch is the same as was used on most (but not all) '68 & 69 Pontiac intakes.

The switch the OP is speaking of was used in both 1970 & 1971. Though they look the same, the '70 version has a different heat range than the 71 version. Either of these thermostatic electrical switches has three spade lugs that come out the top. There is a small jumper harness that plugs into the 3 prong switch & then plugs into the engine harness. On '71 D-port engines with factory AC this switch goes in the tapped hole in the passenger side of the water crossover. The drivers side hole is for the water temp switch, whether idiot light style or rally gauge style. On '71 455 HO cars with factory AC, the three prong switch mounts in the hole in the drivers side of the water crossover. The engine is out of my only '71 keeper with AC, will try & come up with a pic.
Pinion head is offline  
post #7 of 12 (permalink) Old 02-06-2018, 05:12 AM Thread Starter
 
Join Date: Jan 2017
Posts: 166
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 36 Post(s)
A pic would be great. Thank you very much.
Nicholas is offline  
post #8 of 12 (permalink) Old 02-06-2018, 12:10 PM Thread Starter
 
Join Date: Jan 2017
Posts: 166
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 36 Post(s)
Heater control valve

Another quick question. I've been looking at some diagrams and studying schematics in re. to vacuum and electrical involving a/c and heating. I'm starting to figure out some of this but I can't find where the vacuum line from the heater control valve goes to. I'm thinking it goes inside to the heater-a/c switch on the back of one of those ports, but I'm not sure. I know where it ends up alright, but don't know the origin. Would anyone know this?? Thank you.
Nicholas is offline  
post #9 of 12 (permalink) Old 02-06-2018, 04:24 PM
 
Join Date: Jul 2017
Location: Winona, MN
Posts: 174
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 33 Post(s)
Not to hijack this thread, but since PH brought it up. On a 72, does the temp sender go in the crossover too? I asked this somewhere before and someone said in the passenger side head. What is correct?
tjs72goat is offline  
post #10 of 12 (permalink) Old 02-06-2018, 07:16 PM
 
Join Date: Jan 2015
Location: Injun Territory, 'Merica!
Posts: 1,611
Mentioned: 0 Post(s)
Tagged: 1 Thread(s)
Quoted: 121 Post(s)
Quote:
Originally Posted by tjs72goat View Post
Not to hijack this thread, but since PH brought it up. On a 72, does the temp sender go in the crossover too? I asked this somewhere before and someone said in the passenger side head. What is correct?
72 model and later Pontiac V8's took the temp sending unit into the side of the cylinder head. All stock '72 model intakes only has the hole for the Purge valve in the passenger side of the water crossover. The spot on the drivers side was not machined & tapped for a fitting of any kind.
Pinion head is offline  
Sponsored Links
Advertisement
 
Reply

  Pontiac GTO Forum > The 1964-1974 Pontiac Tempest, Lemans & GTO > 1964-1974 Tempest, Lemans & GTO Complete Engine Compartment Discussion

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Pontiac GTO Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in











Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Similar Threads
Thread Thread Starter Forum Replies Last Post
vacuum mode switch on dash a/c heater control ramjet43 1964-1974 Tempest, Lemans & GTO General Discussion 3 06-14-2016 10:58 AM
68 GTO Vacuum Switch Norms68 1964-1974 Tempest, LeMans & GTO Technical and Electrical Wiring 2 02-17-2014 12:58 PM
Changing the thermo diaphragms on a dual snorkel air cleaner mbergin 1964-1974 Tempest, LeMans & GTO Technical and Electrical Wiring 7 03-27-2013 08:22 PM
Vacuum Mode Switch For Heater nicken 1964-1974 Tempest, LeMans & GTO Projects, Barn Finds & Restoration Discussions 4 01-12-2012 09:07 AM
Correct thermostatic vacuum switch? Luiz 1964-1974 Tempest, LeMans & GTO Technical and Electrical Wiring 1 03-15-2008 11:07 PM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome