This 2000 Nissan Xterra came in with the complaint that the a/c works good sometimes but it may not work at all at other times. The easiest place to test is at the thermistor lead connector (white) at the bottom left of the glove box.
It can be done without removing the glove box but it is easier with the glove box assembly out of the way. There are two screws located in the lower corners. Two screws located in the upper corners and two screws located in the upper center at the latch bracket.
The testing is as follows. Key on and engine running with the a/c turned on: Green/orange wire will have battery voltage from fuse #29 in the underhood fuse box, the Blue wire will have battery ground from the a/c control assembly and the Blue/black wire will have a nominal 4-5 volts with the thermistor off (temperature below 40 degrees F) and less than .5 volts with the thermistor on (temperature above 45 degrees F). The thermistor assembly applies a ground to the circuit which is sent through the dual pressure switch and then on to the engine control computer. This one failed the test and needed to be replaced. The proper way is to remove the refrigerant and then the evaporator case but I prefer a simpler way. It can be a little painful but it only takes about ten minutes from this point to change it. There are three phillips headed screws that have to be removed along with three 10 mm headed screws as shown in the following pictures.
Once the screws are removed, the two halves of the evaporator case can be separated enough to look in, see the thermistor, carefully and a little painfully insert your hand into the box and removed the sensor. Slide the new one in, in the reverse order and install the previously removed screws. The long tab pointing down slides into the evaporator fins and tab pointing to the right is the actual thermistor bulb.
Sparky, just changed mine out on my 2000 Xterra. I can’t believe I was able to fit my hand in there…. wow.. and ow… anyways, I’m wondering if it really matters where you put the new one in there. Does it have to be within a few holes of the old one; or just anywhere on the left side? Will it affect the functionality? Thanx..
Icing would only be a comfort factor. The bigger concern would be that the the compressor would continue to operate at very low refrigerant flow. This would starve the compressor of refrigerant and the oil that is carried with it. Ultimately resulting in catastrophic compressor failure.
Sparky, this might seem a little dumb but, isn’t there a way to bypass the thermistor so this problem goes away? I live in Colorado and it is very dry here. The chances of the evaporator icing up are pretty much nil.
The easiest place to start is at the thermistor connector. Check the wiring to see if it matches the info near the top of the post. If it does do the recommended tests. If it tests okay, you would have to move on to checking the pressure switch, relay, compressor clutch and related wiring. Do Not use a test light as you might damage the computer.
I own a 2001 Xterra and the air conditioner is driving me crazy! When it comes on it works great but it does not come on all the time…now i hear a click, click ,click once in a while. It seems like its trying to turn on but it does not and hot air blows out. Please help! Thanks