Air conditioner won't cool

Hi, I just bought a 1994 Cutlass Cierra from a buddy to drive to work. It has 3.1 engine and automatic transmission. The AC won't blow cold air. With the controls on max and temp set to cold, fan set on high, no cold air. I am no mechanic but here goes. Compressor never engages. With AC on and car running, low side pressure reads 55. I have no way to check high side. I find no reading of power at plug in to compressor with a multitester. I checked 2 fuses in car which relate to ac and both are good. Wiring diagram in haynes led me to ac compressor relay. I switched it with other relay on panel, still no compressor engaging. Could you tell me what this sounds like (other than an amateur fumbling around and striking out) Thanks

At 70 degf ambient, static pressure should be about 75 psi-- so you are probably low-- your system needs 47 psi to engage compressor, and your gage is probably inaccurate... Add refrigerant, or find leak and fix leak and then recharge.

It's now 57 degrees outside with engine running, AC on max and high speed and with compressor never engaging. gauge is in blue zone at 42 reading. So am i to understand that because reading is taken while compressor won't run, i should add refregerant despite fact that gauge in blue area says "proper amount of refrigerant"? What should happen when i do this? should compressor start up and reading on gauge actually drop??

You are correct, when you add refrigerant, you compressor should start to cycle on and off. Keep this in mind, refrigerant does not just "disappear" An AC system is a closed system, and it has to go somewhere, so just adding refrigerant will not solve your problem. I recomend adding a refrigerant mix with floresent dye so that you can find the leak fix the leak, then vac and charge.

On a side note, I do not recomend the parts store on charge cable gauges, they are very unreliable. If you are going to charge a system, to should get in contact with someone that has a manifold set of gauges.

Just my thoughts...

Just a side note- don't expect your compressor to ever cycle-- it is a V-5 variable stroke, it DOES NOT cycle by design...it avoids freeze-up not by cycling, but by destroking the compressor....

Your static pressure is low, the blue zone is only meaniful, if the compressor is running- yours is not. Add the refrigerant, look for the leak at the compressor shaft seal- most common area...

I added refrigerant and compressor engaged almost immediately. I haven't checked for leaks yet but will. I really appreciate all the help. this is a great site. thanks again

I appreciate the help with my ac. Someone posted negatively about the quality of cheaper single gauge sets. I have several cars in our family all of which have 134a systems. I am thinking about buying a manifold set for testing and adding refrigerant. I would like accurate readings so I don't damage ac systems. There are quite a number of them for sale on line. I am hoping for some input from some of you. Again, use initially would be to test and add refrig. to cars. Maybe later I would try more sophisticated procedures if required. Thinking i could spend 75 to 150 dollars
1. are some brands preferred
2. pros - cons of aluminum vs brass manifold
3. What is sight glass and is it a desirable feature
4 By the way, I assume that with the manifold type, you can monitor psi while filling??
5 any other advice or reference to reviews or tutorials would be appreciated.
6. I like most people have central air in my home. I assume there is no point is getting gauge that tests R12 or R22 or whatever they use since only hvac technician can obtain such refrigerant???
Thanks, melvinsmellvin