My A/C is cutting on/off intermittently and I've read a lot about the "thermistor" going bad. I don't really drive my xterra that much, so I figured I'd take a stab at replacing this before taking it in and paying an arm and a leg to have the A/C fixed. The problem is, I don't know where the bloody thing goes I can't find it in my Haynes manual anywhere. Anyone point me in the right direction? thanks

I think it's stuck into the cores of the evaporator, inside the cooling box, under the dash/glovebox. Major pain getting to it.
Don't go tearing into it, based on this post, cause I'm not totally sure. Wait for someone who knows for sure. I came across it when I replaced my heater core, so I was pretty deep into my dash when I came across it.
I know when I did my heater core I had to open up the a/c lines in order to get it out, not sure about just the cooling box. You might be able to split that sucker open for access, but I doubt it.

two bills - I've got time to spare this weekend, so I'm just going to attempt the job. Do you think you get at this from inside the car? Like behind the dash/glovebox?

I think you may be referring to the thermo amplifier? If so, I believe it is located inside the evaporator housing. Do you have a pic of the part? I could probably tell you for sure that way.
Does it look like an oversised red plastic toothpick? white coupler?

Anyway, removing the housing is possible. You will swear a lot but you can do it. Getting it back in is the real bitch. (gotta line up the A/C lines with the holes in the firewall, but you cant see the holes and the lines bend easily. A friend would make this 100% easier)

Pull the glovebox, then I believe I unbolted a brace for the airbag. You will see it in your way. couple more bolts and start wiggling. Think of it as a puzzle.

However, to replace that part, (or at least pull the evaporator) you need to disconnect the two A/C lines going into the firewall on the engine side like Two Bills said... As you may know, your refrigerant will leak out (illegal BTW).

So after the part is installed and the evaporator housing back in, your A/C system will need evacuated and recharged.

Wait, it gets better...

Anytime you open the A/C system, moisture will enter it, so the drier needs to be replaced. Nissan calls the part a "liquid tank." (2000 p/n# 92131-0Z800). Fortunately, if I remember correctly, the drier is not real expensive. Unfortunately, your dealer probably wont have it in stock, so it looks like this project will have to wait for another weekend.

Prolific - thanks! The part you described is the part I got. That does sound like a job that will have to wait. Thanks for the detailed information.
SOunds like you did this yourself, how did it go?

Yeah, an "oversized red plastic toothpick". That's what I was refering to. When I discharged my a/c (wrapped a plastic garbage bag around it) and pulled the lines I wire tied a couple of baggies around the lines, to keep the moisture out. Changed the "O" rings before I reinstalled. The lines were off for about 10 days before I did a reinstall and several months before I recharged. No problems that I can see.

Prolificx, I have a couple of questions:
What are the symptoms of a bad drier?
Are a thermo amplifier and a thermistor the same beasts or are we talking about 2 different things here?

For what it's worth, I called up Xterraparts and told them I wanted a "thermistor" and they sent me this part, which seems to also be referred to as a thermo amplifier.

mcoker-

No problem. I actually did not replace the part. I was young and dumb (wait...still am) and I added stop-leak to my A/C system. It ruined everything, so I had to replace each and every component of the system. Not fun. Nothing besides refrigerant or oil will ever come near my A/C again.

On the bright side, I did learn quite a bit about A/C systems. Had I known that this little thermo amp. was so problematic, believe me I would have replaced it.

Once the evaporator housing is out, you undo the screws holding the two halves together. Pull the evaporator out, and the replacement of the thermo amp. should literally take a couple seconds, two of which will be to unwrap the new part.

Two Bills:

How long ago was this that you opened the A/C system? Honestly if it is working properly I think I would just leave it alone. Perhaps you were able to keep the majority of the moisture away with your baggies, and/or the evacuation was done right.

A bad drier doesnt really have symptoms so to speak. The drier has a desiccant bag in it that absorbs moisture. Moisture is an A/C systems worst enemy. (maybe next to stop-leak) It also absorbs corrosion inducing chemicals.

The drier also acts as a filter in our Xterras. The only filter, in fact.

As far as the thermistor, yes I believe all of us are on the same page in this thread. I am looking at a part diagram, and the description is "thermo amp."

A thermistor is just the type of part, much like saying tire/BFG AT.

The confusing part kicks in when someone is talking about a thermistor somewhere else on the truck.

My a/c was discharged for six months (disconnected for 10 days). Had it charged 2 months ago and all seems fine. I'm thinking I might have gotten lucky. Bummer on the stop leak.

BTW, if your radiator or heater core springs a leak a good tempo stop leak is black pepper. Not for a/c units, tho.

Someone e-mailed me privately with some advice on doing this job and said it wasn't that hard... So I went ahead and did it, took about 30 minutes. Basically, when you pull the glovebox/trim, you see the thermo amp wire mounted on the outside of this black box (evaporator? dunno). Unhook it. Take off 4 screws from the bottom half of the box and it will seperate in the middle. Squeeze your hand in there, pull out the old thermo amp, and slide in the new, screw the box back and put your glovebox back. I did this yesterday and my A/C has been working great since then. Although it had intermittent performance before, so I'm not sure that it works fully, but replacing this part was easy. I also ordered the liquid tank... which I didn't replace. I didn't see it from what I took apart.

Damn, that is cool. Sorry for leading you down the wrong lane, I would have never thought you could do it that easily.

The liquid tank is for when you break open the A/C system, which obviously you did not do.

Sorry man.

I feel like an ass, PM me and I will buy that liquid tank from you.

Prolific, I appreciate your responses! Everything I had read everywhere said that this was like a 4hr job. I dunno if people are talking about another job, or if they're just getting screwed by the dealer or what?

Believe it or not, the whites from one or two fresh eggs will work also. Just don't add the yolks

Just an update, my A/C is running strong and has been consistently since replacing this.

I don't suppose you took any pictures? I've been having the same problem for a while. I've got a trip planned for July and would like to get this fixed before then. If I can do it myself that'd be great.

Thanks for your advice here. Same problem...AC was intermittent. Ordered/changed thermistor myself. 30 minutes tops, main time being removal/installation of glove compartment and housing screws. Make a mental note of how and where the old thermistor plugs into the evaporator as your hand has to squeeze in there and installation is mainly by feel. A/C works fine now!
P.S Does anyone know the pressure the low side of the compressor is SUPPOSED to be? I have a gauge attached to the refrigerant can, but nothing in my Chilton manual or the owner's manual gives that information.

Anyone have the part # for this thermistor? My wife's X is having intermittent A/C issues and this sounds like a good place to start. Pressure is good and the high side line was replaced last year.

EDIT: found the number

27675-9Z000 ~$30 from online Nissan parts vendors