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Topic: THERMOSTAT CUT OFF SWITCH

in Forum: C3 Cooling and Heating Systems

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THERMOSTAT CUT OFF SWITCH (8/18)
6/12/08 8:52pm

kstyer

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CUYAHOGA FALLS, OH - USA

Vette(s):
1975 C3 Red, T-Tops, Black Interior. All I need is time and money! Getting there!

Joined: 12/2/2003
Posts: 6424

Your car has an orifice tube and accumulator system. If you are looking at the sensor in the low pressure line with two wires that is the low pressure cutoff switch. If the pressure drops too low, the compressor kicks off. This also controls the compressor cycling. It is not a temp sensor, just pressure. Keep in mind that cycling refrigerant will maintain a temperature relative to pressure, so it does act like a temp switch, but it is not.

Therfore, if the compressor is cycling, the switch is working. You may need to check the freon level, but it sounds like the system is working fairly normally. If the system is full, but not cooling properly you may have some contamination in the system. This could just be air. If that's the case you would need to have it connected to a vacuum pump, and evacuate the system and refill it.

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THERMOSTAT CUT OFF SWITCH (9/18)
6/12/08 9:21pm

my7t1

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Dorr, MI - USA

Vette(s):
71 Colonnade Hardtop Coupe Torch Red with black interior originally L48 built to push around 360hp

Joined: 8/21/2002
Posts: 2581

Like Ken says Joe, if the compressor is cycling, the switch is working. If your suction line is getting that cold, are you getting cold air in the cabin? If the compressor isn't short cycling, and that line is cold, you may not need a charge.

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THERMOSTAT CUT OFF SWITCH (10/18)
6/12/08 9:55pm

79FOREVER
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METAIRIE, LA - USA

Vette(s):
1979 BLACK COUPE

Joined: 6/7/2007
Posts: 144

Ken, the switch has to be a temp. sensor, it is clamped to the outside of the low pressure line going into the bottom of the evaporator core box. I may not be understanding correctly what you are trying to tell me. Agree about contamination, it may have some, have never done anything to the system when I restored the car in the early 90's. Had Freon added a couple of times that is all.

Terry, yes, getting cold air in the cab. It stopped short cycling after running it a while. Is that normal or do I have to be driving the car w/ air going across the condenser?

79FOREVER2008-06-12 18:56:29

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THERMOSTAT CUT OFF SWITCH (11/18)
6/12/08 10:00pm

my7t1

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Dorr, MI - USA

Vette(s):
71 Colonnade Hardtop Coupe Torch Red with black interior originally L48 built to push around 360hp

Joined: 8/21/2002
Posts: 2581

The hotter the abbient temp. the longer the compressor will run witout cycling off. When your moving, increasing the RPM's, and bringing air across your condenser, it will get colder.

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THERMOSTAT CUT OFF SWITCH (12/18)
6/13/08 12:23pm

79FOREVER
Former Member
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METAIRIE, LA - USA

Vette(s):
1979 BLACK COUPE

Joined: 6/7/2007
Posts: 144

Ok, Terry the next time I am dirving I will listen to see if the compressor is cycling after running a while. I think the system is working pretty good, may just need some R12 as discussed. It was a hot day yesterday and I was in my garage running, high 80's easy.

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THERMOSTAT CUT OFF SWITCH (13/18)
6/13/08 1:33pm

79FOREVER
Former Member
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METAIRIE, LA - USA

Vette(s):
1979 BLACK COUPE

Joined: 6/7/2007
Posts: 144

Loaded a pic of my money hole.

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THERMOSTAT CUT OFF SWITCH (14/18)
6/13/08 6:14pm

kstyer

If it has a tube attached and the tube goes into the evaporator housing or attaches to the low pressure hose, there is a sensor bulb attached to the low pressure side. The tube has a small sensor bulb. When heated or cooled gas in the bulb expandes and travels through the tube to make the switch open or close. So it has the exact same effect. These were usually used on slightly older cars. I would not have expected it on a 79. But again, the function is the same, and the results are the same. kstyer2008-06-13 15:14:54

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THERMOSTAT CUT OFF SWITCH (15/18)
6/13/08 8:09pm

my7t1

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Dorr, MI - USA

Vette(s):
71 Colonnade Hardtop Coupe Torch Red with black interior originally L48 built to push around 360hp

Joined: 8/21/2002
Posts: 2581

Sweeeeet Ride Joe. Hope ya can keep her cool Thumbs%20Up

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THERMOSTAT CUT OFF SWITCH (16/18)
6/14/08 11:43am

79FOREVER
Former Member
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METAIRIE, LA - USA

Vette(s):
1979 BLACK COUPE

Joined: 6/7/2007
Posts: 144

Ken,

Maybe, there is a copper or brass metal lead coming off the switch and is clamped to the outside of the lower line, it was not going into the box.

Thanks for the input.

Thanks Terry.

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THERMOSTAT CUT OFF SWITCH (17/18)
7/12/08 8:10pm

Brown78
Former Member
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Ft.Lauderdale, FL - USA

Vette(s):
78 coupe, Dk Brown, ZZ4 385 hp fast burn, steeroid rack/pinion, Keisler 5 speed. Built to run with C5 and C6. on the highway. Can't beat them. But they can't lose me in there mirrors. LOL I built it to enjoy. So far I've tripped through 15 States.

Joined: 6/21/2008
Posts: 31

are you talking about the water shutoff switch with a plastic button on a spring inside the car?? That is connect to the water shutoff down by the heater hoses on the passenger side??

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THERMOSTAT CUT OFF SWITCH (18/18)
7/13/08 10:48am

79FOREVER
Former Member
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METAIRIE, LA - USA

Vette(s):
1979 BLACK COUPE

Joined: 6/7/2007
Posts: 144

No, something different. I don't have what you are describing at all on my 79.

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