What is this?

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Eltommy209

n00b
Nov 27, 2022
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Hello guys need help figuring out what this is and where it goes it’s on a 1978 Monte Carlo I looked on the wiring diagrams on my chiltons book but can’t find it anywhere!
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E794CE90-6394-47F8-A0EF-691EB6431E03.jpeg
 

ELCAM

Royal Smart Person
Jun 19, 2021
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It is a temperature switch. Wired into the low setting on the blower motor. When it is warm the low speed always blows with the key on, when it is cold it turns it off. Sorry didn't check the temperature just know in the summer it conducts and after being in the refrigerator for a while it does not conduct.

Not sure what the purpose was.

Pretty sure this is only on the early cars.

I have seen many of these on the cars but never found a wiring diagram with this switch shown.
 
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Eltommy209

n00b
Nov 27, 2022
2
0
1
It is a temperature switch. Wired into the low setting on the blower motor. When it is warm the low speed always blows with the key on, when it is cold it turns it off. Sorry didn't check the temperature just know in the summer it conducts and after being in the refrigerator for a while it does not conduct.

Not sure what the purpose was.

Pretty sure this is only on the early cars.

I have seen many of these on the cars but never found a wiring diagram with this switch shown.
Thank you so much bro I was going nuts trying to figure out what it was!
 

Ernest

G-Body Guru
Apr 28, 2016
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Texas
It is a temperature switch. Wired into the low setting on the blower motor. When it is warm the low speed always blows with the key on, when it is cold it turns it off. Sorry didn't check the temperature just know in the summer it conducts and after being in the refrigerator for a while it does not conduct.

Not sure what the purpose was.

Pretty sure this is only on the early cars.

I have seen many of these on the cars but never found a wiring diagram with this switch shown.
Well i'll be..... my '79 malibu was doing the same, fan running on low with the key on, engine off when it was warm out during the summer time when i havent even touched any of the AC controls.

So i disconnected the ground wire from the fan itself from under the hood thinking something was screwy with the wiring since the the entire dash was apparently replaced from a different owner awhiles back with a clean non damaged one from different Gbody(MC).
 

pagrunt

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Sep 14, 2014
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Elderton, Pa
I'm guessing the dark color wires are brown so those should be tied into circuit 50 Feed, Ign. Sw. "On" Controlled-Fused, which powers the system. The yellow should be tied into circuit 51Blower Resistor Feed-Low. just as named powers the low speed of the fan. I've never seen this in any car yet dispite all the cars I'ved crawled thru over the past 32 years looking for parts for my Monte. Looked in the wire diagrams I have for '78-'81 & not seen anything either for this. Now there is something in the Camaro digrams in the '78 to '80 but not in '81 for that & it'll run the fan on medium speed. Maybe it was a GMAD option on the production line, late '78/early '79 production feature or a dealer ad on. FYI, looks like that AC13CM has two physical versions, that one & one with a tip.
 
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CopperNick

Comic Book Super Hero
Supporting Member
Feb 20, 2018
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While they could be wires, they could also be plastic hoses. Thing with the A/C is that a lot of it was vacuum driven and those lines feeding that temp switch look large enough and the right colors to fit that criteria. The switch itself would likely be electric and off/on would direct vacuum from the feed or inlet port on the switch to the outs, delivery ports for the various circuits depending on what you want the A-C to do. Think of it a sort of a cro-magnon VOES, or Vacuum over Electric switch and you get a close approximation of what it is meant to do. Not shown on an electrical diagram means you might have to peruse the A/C or heater circuit diagrams to find it. Be very kind to that switch, it is old and likely to be on the unobtanium list when it comes to getting a new one.



Nick
 
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ELCAM

Royal Smart Person
Jun 19, 2021
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Well i'll be..... my '79 malibu was doing the same, fan running on low with the key on, engine off when it was warm out during the summer time when i havent even touched any of the AC controls.

So i disconnected the ground wire from the fan itself from under the hood thinking something was screwy with the wiring since the the entire dash was apparently replaced from a different owner awhiles back with a clean non damaged one from different Gbody(MC).
Just unplug the thermal switch and it will stop running when you didn't turn it on. Everything still works just fine without it.
 

ELCAM

Royal Smart Person
Jun 19, 2021
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I've never seen this in any car yet dispite all the cars I'ved crawled thru over the past 32 years looking for parts for my Monte.
I'm thinking this is a desert thing. Most cars I see were sold in the southwest desert. TX, NM, AZ, NV.
 

ssn696

Living in the Past
Supporting Member
Jul 19, 2009
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Not vac hoses. Too close together. Those are big, fat, high-current wires - makes sense that they would be tied to the blower motor.
Keep up the good advice.
 
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