Mharvey500

Hi, I am trying to replace the thermostatic switch 27723-4P000 on a 2000 Infiniti i30. I don't know how to separate the plastic shroud around the evaporator enough to access it. Taking out all the bolts and screws I can see, except for one at the top/back of the case which requires a swivel joint to get a socket on it. Do I need to remove that one at the top/back? The best I can do is reach in with a screwdriver and push the old defective switch. It is firmly attached to a clip which is attached to the fins of the evaporator. I don't want to break anything, and I would like to know how to get the best access to this switch.

Mharvey500

The answer is to mount the new switch in the hole of the evaporator box for the wire of the old switch. It is held in place by tightening the evaporator box screws. The effectiveness is proven by well performing a/c system. It is an item that seldom fails, but after 20 years and so few of these vehicles remain few have experienced it. I suppose the technique could hold for other vehicles. You don't really need to mount it on hard to reach evaporator fins as long as it is in the same air flow.

User1

Is this the switch that cuts the compressor when the evap coil reaches a certain temp? Is the fact that I don't have one of these the reason my damn suction line keeps freezing over??????? I have been wondering about this switch since I got my AC going!!!! I rebuilt the entire system myself and have no recollection of ever seeing this switch!!!! I was wondering what the hell was going on! I swear I did not unplug this switch or even see a harness connector for it when I removed my air box to replace my evap coil??? But here it is on the diagram???

https://www.nissanpartsdeal.com/part...g-unit,,27723N

User1

Hold up:

It appears that the switch is only required for auto controls, it is not present in the manual controls diagram. Maybe I'm not losing my mind after all and I need to put a proper charge in my system instead of guessing the refrigerant weight

https://www.nissanpartsdeal.com/part...tml?PNC=27620P

User1

Sooooo, that brings the question, for which I have been unable to find an answer in the FSM or anywhere else, what DOES the '02/'03 system use to cut the compressor? Or does it just run continuously when on lowest AC temp setting? I have researched this and could not find a sensor or switch for this purpose and determined that the system runs continuously, and that my occasional frozen suction line was me being in a hurry to charge the system and just dumping 134a into it till I liked the pressures (yes, i use T&P charts with humidity)

Mharvey500

My experience with disconnected switch is need to set the climate control thermostat to coldest setting, in my case 18 celcius, to get decent cooling, and I would manually adjust fan speed so it wouldn't go full blast. There was no freezing, but then my system has a full charge of refrigerant. With a good switch installed the climate control thermostat works like it should at any temperature setting automatically adjusting fan speed.

User1

Cool. But what about for us manual control system users? According to the diagrams, this switch is not a component within a manual control system.

Mharvey500

I once overcharged refrigerant and the compressor would not run at all until I removed a little refrigerant. My guess is the compressor on/ off is controlled by other sensors than the thermostaic switch, especially since it is not present in manual controlled systems.

User1

I understand. Also interesting is that my 2003 system does not have a low pressure switch. So, there are no other switches. I've been curious since I removed my engine for the swap. I guess this system just runs indefinitely when the AC switch is on and depends on an accurate charge to not freeze over. Nothing as advanced as a system which cycles the compressor using temp data. I read somewhere that the low pressure switch may be built into the compressor, but I don't remember where I read that or if it was even relevant to our compressors, and my system works great, so I don't really care enough to dig deep at this point. Although I am **** enough that I do have a thermometer in my dash vent and watch vent temps every time the AC is on Eventually I'll figure out what this system uses for low side switch and compressor cycling... Someday.. Maybe..

Mharvey500

I became curious about my a/c, if it was cycling on and off, and sure enough it stays on all the time I am requesting a/c. This a/c is working perfectly. Now I used to have an Odyssey which did cycle on and off so I was expecting my infiniti to as well. A little google search pulled up this thread, https://oldsmobileforums.com/forums/...ad.php?t=13883. It seems there are two kinds of systems in use in different makes of car, and it should be expected to be completely normal to be on all the time depending on your make.