Air Conditioning question

[Racincc85]

I've been having some trouble with the A/C system on my 1999 nissan altima. There is a temperature sensor on the evaporator that cycles the compressor to prevent the condensation on the evaporator from freezing up. The problem is that this temperature switch is set way to conservatively which causes the compressor to cycle too often and prevents the a/c from cooling well. I bypassed the switch and the air got extremely cold so I know for sure the issue is with this switch. Unfortunately there is no adjustment on this goofey thing. I read a post on an altima specific message board where someone replaced the switch with an adjustable one but I was unable to contact the person to get more information. I've searched high and low on google for one but couldn't find a thing. Does anyone know where I could purchase something like this? If not, I was thinking of modifying the existing switch by throwing a resistor inline between the temp probe on the evaporator and the switch to fool it into thinking the evaporator is warmer than it actually is. If anyone could help me with that I would appreciate it. Thanks!

[MagicRat]

I hate to state the obvious, but it's possible your existing switch is defective and is not performing to factory spec. You might be able to swipe one from a wrecking yard if the dealer wants too much money for a new one.

As for the adjustible unit, try installing a potentiometer (??) in series with the probe. Essentially this isa variable - resistance old-style volume controller, used in older stereos and hobby type radio kits. Radio Shack used to show them in their catalogue a few years ago, and may still do.

[Racincc85]

I checked the switch and it was performing to factory spec. It seems nissan just wanted to be extremely conservative on the specs for some bizzare reason. Good idea with the potientiometer. I'll pick one up this weekend and give it a try. Thanks for the help!

[Racincc85]

I finally got around to working on the car this past weekend. It turns out that the system works opposite from the way that I thought. As the evaporator temperature drops, the thermisistor increases its resistance and cuts off the compressor so installing a potientiometer did absolutely nothing. Instead what I did was disconnect the thermisistor probe from the switch and connect them together so the switch thinks the evaporator is always warm and lets the compressor run all the time. After doing some reading it seems the worst that can happen is moisture condensing on the evaporator can freeze and block airflow. To get around this problem, I've been using the system in the recirculate mode all the time so that humid air is not continuously drawn in lowering the chance of the evaporator freezing. I used the system for about 2 hours this way a few days ago and it worked great. Just wanted to post the results in case anyone else is having a problem like I was.

[Moppie]

I know someone who did that to an early 90s Honda Accord.
It worked really well, still it started snowing. Inside the car.