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adjustable cycling switches?

fastrc2 on Wed September 05, 2007 5:46 PM User is offlineView users profile

i have seen many posts on here lately about adjustable cycling switches. now this adjustment sets the pressure at which the low side drops to before the compressor cut out is activated. so if that is the case what is a good pressure to be set at i have been hearing low 20's as a setting, and now i would like to know are they on hondas? i have a 98 civic and a 93 del sol, which i know are both cycling systems with txv's and i am wondering if they are to be adjustable, also i installed the entire system in the 1998 civic, should this have needed to be adjusted on install. i hope so, since i installed the system it has always seemed to be slightly warmer than i prefer.

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wish in one hand, poop in the other see which fills first.

Chick on Wed September 05, 2007 5:50 PM User is offlineView users profile

The cycling switches you are referring to are those used on O tube accumulator systems, not TXV's which use diferent methods to cycle the compressor, such as evaporator temp sensors..

PS: expansion valve systems seldom cycle since the expansion valve "meters" the flow of refrigerant to the evaporaotr...Hope this helps..

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

Edited: Wed September 05, 2007 at 5:52 PM by Chick

fastrc2 on Wed September 05, 2007 6:22 PM User is offlineView users profile

when i installed the system and wass putting in the evaporatior i belive i noticed the preinstalled evaporator temp sensor,[or maybe it wa the txv sensing bulb?] i dont remember i wanna say it was the sensing bulb, it was not on the evaporator, and i think i pushied it inbetween the edges of the evaporator fins. would this have been a horrible idea? or was it supposed to get the air off of the evaporator?

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wish in one hand, poop in the other see which fills first.

NickD on Wed September 05, 2007 7:07 PM User is offline

Purpose is to prevent evaporator freeze up, in a CCOT system that uses these adjustable cycling switches, well, some are adjustable, once the low side pressure goes down low enough to freeze the evaporator, they open and shut down the compressor, typically 25 psi for R-12, and 21 psi for R-134a. They don't switch on again until the pressure exceeds about 45 psi.

You have an expansion valve system that has the advantage of less wear and tear on the compressor with less cycling, the expansion valve closes as demands decrease especially in cooler weather keeping the low side pressure up, but has the disadvantage that the evaporator can freeze up. So a second thermostatic switch has to be added that kills the compressor if the temperature gets below 33*F and turns it on again once the evaporator temperature hits about 39*F. You can mount a thermocouple device to the evaporator inlet and check if these temperatures are correct. I feel your problem is loss of refrigerant that also reflects poorer cooling, suggest you check that first. Other causes are dirt and debris in the system, condenser and evaporator fins covered with fuzz and other junk that slows down air flow. System has to be cleaned first before testing pressures plus fans must be operating correctly, otherwise, any pressure readings you see will be false.

Hope this gives you a better understanding.

fastrc2 on Thu September 06, 2007 6:12 PM User is offlineView users profile

so on my honda how is it normally supposed to be i also want to know what effect it has if i want to say it was the sensor bulb for the txv, it is not on the low side line it was originally in the air after the evaporator, and when i put it in, i pushed it over and in between the fins of the evaporator, hopefully for a more accurate reading, i wonder if this is causing it to always stay a little warm?

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wish in one hand, poop in the other see which fills first.

Chick on Thu September 06, 2007 6:49 PM User is offlineView users profile

The factory desgin is how you should mount the new one..either attached to the oulet (suction/tailpipe or whatever) and that is how/what it reads, by the temp of the suction line..Not the evap itself, unless like some, it is mounted in the middle of the evap..towards the outlet, but put it where the old one was.........

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

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