# 02 altima a/c fails ONLY when its humid out... WTF???



## abrown250 (Apr 25, 2007)

so ive got an 02 altima 2.5s. the a/c fails ONLY when its humid out (rainy, foggy, snowy, etc). which is kind of a big problem cause thats when i need it for the defroster. no one can replicate the problem (mainly cause it isnt humid out when i take it in) thus they cannot diagnose the problem. so im stuck with an a/c that fails when it rains out, and im about 1,000 miles away from the end of my aftermarket warranty thatll more than likely cover whatever problem it is.
Does ANYONE know wtf the problem is?????


----------



## jo31b (Oct 24, 2007)

When you say "fails" do you mean just stops working completely? Does your clutch engage at all?

Does the moisture drain from the car properly?

Depending on how much humidity we are talking about, most of your system's effort is spent removing the water from the air. So if it is very humid with warm temperature, then its capacity to remove moisture and cool the air is reduced to a minimum.

If the system is not cycling off soon enough, your Evaporator in the car may be clogging with Ice from the water freezing in it. 

If your refrigerant charge is low from a leak or from a technician not following directions, you will have cool air when there is no real demand on the system, and outside temperature air with some moisture left when a demand of humidity is placed on the system. The air temperature will be still warm and less humid.

But if your system is overcharged and the pressure is too high when the system is used in demanding conditions, the high pressure switch will shut off the system.


Can you let us know exactly what happens to the system?

Does it fail completely? (all warm air, full humidity and compressor clutch not engaged)

Is the air flow reduced from the vents when it fails?

Is your Condenser in front of your rad free of all debris?

When the system fails is your condenser very hot? (hot will tell you that at least your compressor is/was circulating the refrigerant)

If you have a food style thermometer you can check your system's performance: Pg HA-51 98 Altima Service manual

Conditions to be met-

-Vehicle Indoors, or in the shade (well ventilated area)
-All doors closed
-All windows open (well the book says "door window" I'm guessing they are missing an "s" because they don't say which door window, I guess if your test fails, try it again with just the driver's door open)
-Hood open
-Temperature setting Max Cold
-Air flow from Face Vent
-Recirculation switch pressed
-Blower speed High
-A/C On
-Engine RPM 1500
-Minimum air temp outside of car 20*C(68*Fa)

Operate the A/C for 10 minutes before measuring air temp.

Stick the thermometer shaft into the centre outlet just to the right of the instrument panel and measure the temperature to the point when the needle stops going down.

These are the numbers you are looking for

50-60% relative humidity for the outside air 
20*C (68*F) outside Air / outlet temp 4-5.4*C (39-42*F)
25*C (77*F) outside Air / outlet temp 4.2-5.6*C (40-42*F)
30*C (86*F) outside Air / outlet temp 8.5-11.1*C (47-53*F)


60-70% relative humidity for the outside air
20*C (68*F) outside Air / outlet temp 5.4-6.8*C (42-44*F)
25*C (77*F) outside Air / outlet temp 5.6-8*C (42-46*F)
30*C (86*F) outside Air / outlet temp 11.1-14.1*C (52-57*F)

If your numbers do not match someone is not even taking the time to do this simple step for you when you are paying them to fix the problem.

The causes could be:

-restriction somewhere in the refrigerant system.

-system overcharged/undercharged

-Evaporator clogging with Ice/Partially clogged with dirt/leaves/mouse nest (but you would notice reduced air flow for this)

-Conderser clogged/Rad Fan not operating properly

-Compressor operating on minimum stroke

-Triple pressure switch (senses high and low pressure, turns on the radiator cooling fan to keep refrigerant pressure low)

-Excessive Compressor lubricant (this happens often when tecnicians forget to measure how much oil came out of the system when they evacuated the refrigerant and just guess how much oil to put back in) If you follow your system and notice faint stains on any of the hoses where the metal crimps to the rubber, or where hoses screw on to components that is evidence of a system with too much compressor oil. Be careful some hoses are very hot, it is best to check for this with the engine off and cold (not driven for more than 6 hours)

-or something that I can't think of off the top of my head


DO NOT OPEN THE SYSTEM AT ALL. Not only is it a bad idea to open the system, it is against the law.

You will get severe frost bite if you open the system without evacuating it with the proper equipment. You will also pay very large fines if you open the system and get caught.

That's all I have for now, I really can't say without looking at the car with the proper equipment.


----------



## abrown250 (Apr 25, 2007)

the ac fails completely. when it works i can feel the clutch kick in and the bit of strain on the engine, but when it fails, the a/c light is on but the clutch never kicks in. the air flow is never affected. one dealership flushed out and replaced the coolant fluid hoping that would do it. other than that, the 2 dealerships ive gone to were unable to replicate and/or find out the problem. one of the reasons being that it was dry both times i had it looked at.
outside temperature has no affect on it, just the humidity. which sucks because im basically blind in the rain cause my defroster wont work.
i dont know what a food thermometer is but i dont have climate control or anything, and no temperatures are displayed, just a dial with the red and blue bar around it.
also i have a 2002 altima, not a 98 as you pointed out when referring to the service manual. ummm... thats about all i can tell about the symptoms and whatnot. ive no idea otherwise


----------



## jo31b (Oct 24, 2007)

The image here is an example of a food thermometer. I don't know the technical name. I guess I should have posted that the first time. The kind you would use to get the temperature of meat while cooking, like a turkey.

You stick the shaft of the thermometer into the air duct just to the right of the Gauge cluster.

Two dealerships you say? Well if they can't find it by seeing how your system pressures are, then it probably has to do with the moisture and one of the electrical wires or connectors. 

That's pretty frustrating that more than one dealer didn't find the problem for you. Pretty sad too. There is only so much that can go wrong in an A/C system. I would write a complaint about those two dealerships to Nissan USA because if anybody is supposed to be able to fix these cars, it's them.

Sorry I can't be more help.

Good luck.


----------



## jserrano (Oct 27, 2004)

You don't need the rain to come to you to troubleshoot electrical problems having to do with humidity. Instead you bring the rain...I mean, have the technician take a spraying bottle full of water and have him go through all the electrical connection points that is part of the AC system. You just need a mist of water vapors so don't drench down everything. And beware of the ignition system and other components. Good luck.


----------

