1995 Maxima – Can’t Get AC Beyond 25psi

[mymaxima99]

My 1995 Maxima’s climate control isn’t as cold as it was when new. I’ve never performed any service of any kind on it. I recently put 2 cans of R-134a into it (for the very first time) and the psi only moved from approximately 21psi to 24psi. (I did add the R-134a properly with the climate control set at 65 degrees on a hot day with the windows/doors open so that the compressor was on at the time). My Haynes service manual says never to add more than 2 cans. The air is considerably colder coming from the vents now, but I was hoping to get the psi between 25 and 45 (which my id AC/CPRO charging gun instructions recommends). Any thoughts on why I couldn’t get my psi higher are appreciated. Thanks in advance.

[AZhitman]

Is that the high side or low side reading? Did you monitor both ports?

Normal low side readings with A/C on and engine speed at 1000 rpm are 25-35 psi. High side under the same conditions should be 200-350 psi.

Remember, the LOW pressure side is cold, and the HIGH pressure side is hot.

[mymaxima99]

AZhitman....yes, my gauge/gun is only capable of measuring the Low (cold) side and I was careful to make sure that I was on the Low (cold) port (from the photo in my Haynes 1995 Maxima service manual).

[AZhitman]

Sounds like you're ok, then. The only way to see what's going in is hooking up proper manifold gauges - the differential is critical, which a "one-side" gauge doesn't show.

Adding freon is typically unnecessary, and most AC experts advise against those "quick fix" kits. The system should be evacuated completely and THEN refilled.

There are plenty of other reasons for an A/C system to not function at max efficiency (that don't have anything to do with freon).

#1 - Air not getting to/through the condenser. This is pretty easily remedied, and something I do annually on ALL our cars - It may require removing the radiator, but getting in behind the condenser and flushing all the bug/dirt/pebbles (from the backside, opposite the airflow direction) is a huge deal.

#2 - If your car has a cabin filter, change it. If you need the FSM for your car, you can look it up at www.nissanservicemanual.com

#3 - Compressor issues. This is unlikely, but it's always a possibility. I'm betting on #1 or 2.

[mymaxima99]

Last night when tempertures were in the low 80s, the climate control worked very well and was cold!!!.....and the compressor stayed on. However today, the temperture was in the 90s and my compressor kept turning on and off every few seconds. I googled my new problem and it appeared I may have put too much R-134a in my system. I rechecked the psi on the low side today when the compressor was on, it was over 45!!!! (it was around 25 yesterday!....I don't understand how it could have increased since I checked it yesterday). How can I remove some of the excess R-134a?
Also, thank you AZhitman about your advice on cleaning the condenser....I hadn't done that....and I don't have a cabin filter by the way.
I also just found this: http://www.nicoclub.com/FSM/Maxima/1995/ha.pdf It appears to say that at 95 degrees, that the lower psi should be between 23 and 27 (on HA-31 page 957).

[AZhitman]

Yep - Time to take it in for an evacuation / recharge. They only charge for the amount of Freon they add, so you shouldn't have much of a bill. See if you can find a local coupon...

A/C is one of those systems where it really pays to let a pro handle it. Screwing it up means big $$$ to replace it. Too much pressure can damage the compressor, seals, and the orifice valve (none of which are cheap).

Props for giving it a shot, though!

[Jacqueline.anna]

Well usually like below 30 degrees or 25 degrees it just starts to have problems turning on. Like i crank the engine and nothing so i let the ignition switch on the on position for about 10 minutes then i try again and i hit the gas pedal and sometimes the battery almost dies untill it turns on.

[NutriaforBreakfast]

http://www.nicoclub.com/archives/air-co ... finit.html

some additional info under tech pages