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Chevynut · 10-09-2007, 01:39 AM

Can someone familiar with A/C tell me what the individual 4 wires do on a trinary switch? I know it turns off and on the A/C compressor if the pressure is too high or too low and another lead is used to turn on a fan. But how exactly is it wired in and does it ground the fan signal or supply 12V? Does it depend on how you wire it? Where do all 4 wires go? I can't seem to find anything on the web.

My assumption is that 2 wires are used to engage and disengage the clutch, in series with power to the clutch, and the other two are used to turn off and on the fan so you can wire one side to either 12V or ground and the other to the fan relay. Is that right?

Rick_L · 10-09-2007, 08:19 AM

There's lots of ways to use the switch.

The pressure functions would usually be wired in series with the compressor power wire. The pressure portion of the switch is closed when operation is normal. The switch opens when pressure is too low or too high.

The fan function of the switch closes when the a/c head pressure reaches a set value. You can use this with a relay to either ground the relay coil or to provide power to it.

Chevynut · 10-09-2007, 12:21 PM

Thanks Rick, that's what I thought given that there were 4 wires. Looks like there are basically two SPST switches with each end available.

10-09-2007, 01:39 AM	#1
Chevynut member Join Date: Jan 2007 Chevynut's Garage Location: Fort Collins, CO Posts: 12,277 Member #1769	Trinary switch operation? Can someone familiar with A/C tell me what the individual 4 wires do on a trinary switch? I know it turns off and on the A/C compressor if the pressure is too high or too low and another lead is used to turn on a fan. But how exactly is it wired in and does it ground the fan signal or supply 12V? Does it depend on how you wire it? Where do all 4 wires go? I can't seem to find anything on the web. My assumption is that 2 wires are used to engage and disengage the clutch, in series with power to the clutch, and the other two are used to turn off and on the fan so you can wire one side to either 12V or ground and the other to the fan relay. Is that right?

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10-09-2007, 08:19 AM	#2
Rick_L Trifive Leaders Club Join Date: Mar 2007 Rick_L's Garage Location: Katy, TX Posts: 20,239 Member #2256	There's lots of ways to use the switch. The pressure functions would usually be wired in series with the compressor power wire. The pressure portion of the switch is closed when operation is normal. The switch opens when pressure is too low or too high. The fan function of the switch closes when the a/c head pressure reaches a set value. You can use this with a relay to either ground the relay coil or to provide power to it.

10-09-2007, 12:21 PM	#3
Chevynut member Join Date: Jan 2007 Chevynut's Garage Location: Fort Collins, CO Posts: 12,277 Member #1769	Thanks Rick, that's what I thought given that there were 4 wires. Looks like there are basically two SPST switches with each end available.

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