Speed Sensor and air conditioning problem

[Curth]

I have a 1995 Altima. The air conditioning, when turned on full blast, does not work or when it is on part of the way. I checked the charge on the low side with a kit air gauge and it was in the normal range. The compressor kicks on for maybe a second or so every minute or so when the air is turned on, but it does not stay engaged. I would think that it would have to stay engaged to cool and it is not.

Second, I have a speed sensor failure code that keeps setting. I have not yet removed it and checked it as I have read about.

Thanks

[JustSayGo]

You are right. The compressor needs to run for a few minutes to cool. Low-side A/C pressure is measured after the compressor has run long enough for the pressure to stabalize or read just before the compressor cycles off. Even 10 seconds isn't enough time to check the pressure accuarately. Sounds like you are describing an A/C system that is empty. As soon as the compressor clutch turns the compressor, low-side system pressure drops and the low pressure cut out switch cuts power to the clutch. If there is any restriction in the service can hose or at the schrader valve the guage won't drop with the low-side pressure.

[Curth]

Obviously, I know little about automotive air conditioning. Would you suggest that I continue to add refridgerant until the low pressure switch makes and then try to get a reading on the gauge of the level of charge?
Something else that I left out earlier was that the belt had worn out earlier this year when the air was not needed, so I cut it off. Now that I have more time and the weather is hot, I put a new belt on and I am trying to service it.

If I should add more refridgerant, should I also add a can of lubbricant? I have been advise to do this.

Thanks

[JustSayGo]

When did the A/C last work? You could jump accross the low pressure switch or plug and read the gauge on the service can. If it shows a vacuum or very low PSI, the system is more than a little low on freon. My concern would be that there is a leak and that whatever I pay for freon will be lost and it still won't cool any air. If all the freon has leaked out because of a leak there is probably air and some moisture in the system. Systems filled with air that has warmed and increased pressure can show pressure high enough for the switch to connect for a second. Don't add oil. A slow leak won't carry oil with the freon as it escapes. No sign of oil leaking from any part of the A/C? R134a makes it very difficult to find a leak for that reason. Ultra-violet dye and a powerfull UV light are the tools that make finding leaks easier. The most common place for any A/C system to leak is at the compressor seal because it is a moving part. An overcharged system or radiator fans not working will increase high side pressure and could shred the A/C belt or the belt could just have worn out.