Thermostat Housing Switch - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**71CHEVYSHORTBED402** · 01-26-2023, 07:10 PM

Just curious if anyone still has the complete assembly, and if you do props, does it work

. I may never assemble one, but I'm wondering, what do the lines route to? Thanks.

Looks like this, perhaps

ray_mcavoy · 01-26-2023, 07:48 PM

I believe that's off a newer engine ... probably mid/late 70's or 80's ... not original for 67-72.

Those thermal vacuum switches (TVS) were used to control a variety of things ... like EGR valves and other emissions equipment.

**kwmech** · 01-26-2023, 07:57 PM

Quote:

Originally Posted by ray_mcavoy

I believe that's off a newer engine ... probably mid/late 70's or 80's ... not original for 67-72.

Those thermal vacuum switches (TVS) were used to control a variety of things ... like EGR valves and other emissions equipment.

Sometimes even the vacuum advance on the dist.

**71CHEVYSHORTBED402** · 01-26-2023, 09:17 PM

Quote:

Originally Posted by ray_mcavoy

I believe that's off a newer engine ... probably mid/late 70's or 80's ... not original for 67-72.

Those thermal vacuum switches (TVS) were used to control a variety of things ... like EGR valves and other emissions equipment.

Pretty sure that housing is 336790, which shows for a number of truck years, including 71-72. But the switch might be different.

Might be worth mentioning the housing I removed from my 1971 is cast iron, stamped 1595. It's vintage IMO, though I'm not sure it's truck original, and it doesn't have female threads for a switch.

ray_mcavoy · 01-26-2023, 11:42 PM

Quote:

Originally Posted by 71CHEVYSHORTBED402

Pretty sure that housing is 336790, which shows for a number of truck years, including 71-72. But the switch might be different.

Yes, the GM parts catalogs could very well list that newer style thermostat housing as a service replacement part for earlier years. The installer would simply have to put a pipe plug in the unused hole.

In fact, GM did that from the factory (pipe plug in that hole) on mid/late 70's trucks that were over the GVW threshold to be considered "heavy duty" and didn't require as much emissions equipment as cars & lower GVW trucks.

**71CHEVYSHORTBED402** · 01-27-2023, 01:30 AM

Quote:

Originally Posted by ray_mcavoy

Yes, the GM parts catalogs could very well list that newer style thermostat housing as a service replacement part for earlier years. The installer would simply have to put a pipe plug in the unused hole.

In fact, GM did that from the factory (pipe plug in that hole) on mid/late 70's trucks that were over the GVW threshold to be considered "heavy duty" and didn't require as much emissions equipment as cars & lower GVW trucks.

I see. I searched 336790, and it comes up on vehicles from 1966 to 1979. Are you saying 67-72 came without female threads? As I mentioned earlier, the cast iron pulled from my truck was without threads.

ray_mcavoy · 01-27-2023, 05:43 PM

Quote:

Originally Posted by 71CHEVYSHORTBED402

Are you saying 67-72 came without female threads? As I mentioned earlier, the cast iron pulled from my truck was without threads.

I can't say with 100% certainty, but I don't think 72 & earlier thermostat housings originally had that female threaded hole in them. I've seen both iron and aluminum versions of the housings without the hole ... I don't know if that was something that changed after a certain year or if it varied by application.

leftybass209 · 01-27-2023, 06:41 PM

The 350/350 in my 72 had the original intake, water neck, and quadrajet, and was an A/C and CA emissions born truck, but no extra provisions in the cast iron water neck.
I only lend the extra info because as we've found out on these trucks before... sometimes it's just a goofy combination of parts ordered that requires different parts like this.

RichardJ · 01-29-2023, 02:18 PM

I use one of those to control one of the electric pusher fans. The switch is a 208* switch from a Honda Accord. I had to make the thread adapter. The other fan is controlled by the AC. Both fans are from '90s Cadillacs.

**Palf70Step** · 01-29-2023, 06:22 PM

My 81's 250 6 had that. Mostly for smog stuff. I think I still have them. I've seen them use the thermostat housing for a seperate temp sensor for electric fans.
Ibelive the 6 stuff will work on small block also.

**special-K** · 01-30-2023, 08:48 AM

That is a newer housing. 67-72s didn't have that stuff. A story: I used to stop in the my Chevy dealer on a regular basis to have the parts guy look up parts availability and order what was available. One day I had him check 69-72 truck steering wheels. "It shows they are available but only in black". I couldn't get the words "Order me up one" out of my mouth fast enough. It came in as the current '80s truck steering wheel. That's when I learned GM's concern for supplying parts for their vehicles is offering what will work, not what is correct for a restoration. They print supplemental parts books to list superceded parts numbers for depleted parts numbers

**71CHEVYSHORTBED402** · 02-05-2023, 08:31 PM

Thanks for the education

I forget or never knew. Original housings have a hole for a spring I guess, what for?

**Steeveedee** · 02-05-2023, 09:03 PM

Quote:

Originally Posted by 71CHEVYSHORTBED402

Thanks for the education

I forget or never knew. Original housings have a hole for a spring I guess, what for?

That was for the throttle return spring on a lot of vehicles.

**special-K** · 02-06-2023, 07:52 AM

I really like those housings with the tab & hole for return spring. I keep those when I find them

KQQL IT · 02-06-2023, 12:52 PM

Some opened/closed the hot air stove door in the air cleaner.

01-26-2023, 07:10 PM	#1
71CHEVYSHORTBED402 Senior Member Join Date: Feb 2009 Location: Northern Nevada Posts: 7,118	Thermostat Housing Switch Just curious if anyone still has the complete assembly, and if you do props, does it work. I may never assemble one, but I'm wondering, what do the lines route to? Thanks. Looks like this, perhaps Attached Images __________________ Tony 71 Custom Deluxe, SWB, 2WD, 402, A/C. I developed an assm. guide "kit" for restoring it from ground up. With assys, the guide accts for 1000s of OEM identifications and part numbers, all written in short order. 700+ images include assm, illust., charts, and points of interest. Much of the info. applies to all 67-72 GM trucks, and to a lessor degree all 67-72 GM vehicles. My build thread, and more on the guide https://67-72chevytrucks.com/vboard/...d.php?t=730025 Last edited by 71CHEVYSHORTBED402; 01-26-2023 at 09:52 PM.

01-26-2023, 07:48 PM	#2
ray_mcavoy Registered User Join Date: Nov 2009 Location: Sherman, ME Posts: 2,354	Re: Thermostat Housing Switch I believe that's off a newer engine ... probably mid/late 70's or 80's ... not original for 67-72. Those thermal vacuum switches (TVS) were used to control a variety of things ... like EGR valves and other emissions equipment.

01-27-2023, 06:41 PM	#8
leftybass209 Registered User Join Date: Feb 2011 Location: Modesto, CA Posts: 2,185	Re: Thermostat Housing Switch The 350/350 in my 72 had the original intake, water neck, and quadrajet, and was an A/C and CA emissions born truck, but no extra provisions in the cast iron water neck. I only lend the extra info because as we've found out on these trucks before... sometimes it's just a goofy combination of parts ordered that requires different parts like this.

01-29-2023, 02:18 PM	#9
RichardJ Registered User Join Date: Apr 2010 Location: So Cal Posts: 1,413	Re: Thermostat Housing Switch I use one of those to control one of the electric pusher fans. The switch is a 208* switch from a Honda Accord. I had to make the thread adapter. The other fan is controlled by the AC. Both fans are from '90s Cadillacs. Attached Images __________________ '67 GMC 2500, 292, 4spd, AC

01-29-2023, 06:22 PM	#10
Palf70Step State of Confusion! Join Date: Jul 2002 Location: Gulfport, MS USA Posts: 46,640	Re: Thermostat Housing Switch My 81's 250 6 had that. Mostly for smog stuff. I think I still have them. I've seen them use the thermostat housing for a seperate temp sensor for electric fans. Ibelive the 6 stuff will work on small block also. __________________ 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!

01-30-2023, 08:48 AM	#11
special-K Special Order Join Date: Nov 2004 Location: Mt Airy, MD Posts: 85,863	Re: Thermostat Housing Switch That is a newer housing. 67-72s didn't have that stuff. A story: I used to stop in the my Chevy dealer on a regular basis to have the parts guy look up parts availability and order what was available. One day I had him check 69-72 truck steering wheels. "It shows they are available but only in black". I couldn't get the words "Order me up one" out of my mouth fast enough. It came in as the current '80s truck steering wheel. That's when I learned GM's concern for supplying parts for their vehicles is offering what will work, not what is correct for a restoration. They print supplemental parts books to list superceded parts numbers for depleted parts numbers __________________ "BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed" GMC '67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi.........."The '67" (project) GMC '72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok..."The '72" (rolling) Tim "Don't call me a redneck. I'm a rough cut country gentleman" R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586 ~ 67ChevyRedneck ~ Grumpy Old Man ~

02-05-2023, 08:31 PM	#12
71CHEVYSHORTBED402 Senior Member Join Date: Feb 2009 Location: Northern Nevada Posts: 7,118	Re: Thermostat Housing Switch Thanks for the education I forget or never knew. Original housings have a hole for a spring I guess, what for? __________________ Tony 71 Custom Deluxe, SWB, 2WD, 402, A/C. I developed an assm. guide "kit" for restoring it from ground up. With assys, the guide accts for 1000s of OEM identifications and part numbers, all written in short order. 700+ images include assm, illust., charts, and points of interest. Much of the info. applies to all 67-72 GM trucks, and to a lessor degree all 67-72 GM vehicles. My build thread, and more on the guide https://67-72chevytrucks.com/vboard/...d.php?t=730025

02-06-2023, 07:52 AM	#14
special-K Special Order Join Date: Nov 2004 Location: Mt Airy, MD Posts: 85,863	Re: Thermostat Housing Switch I really like those housings with the tab & hole for return spring. I keep those when I find them __________________ "BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed" GMC '67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi.........."The '67" (project) GMC '72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok..."The '72" (rolling) Tim "Don't call me a redneck. I'm a rough cut country gentleman" R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586 ~ 67ChevyRedneck ~ Grumpy Old Man ~

02-06-2023, 12:52 PM	#15
KQQL IT At the body shop. Join Date: Aug 2009 Location: Land of fruits and nuts. Posts: 5,130	Re: Thermostat Housing Switch Some opened/closed the hot air stove door in the air cleaner. __________________ " That didnt make it any newer " " Dont antique the equipment "



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