a/C high and low pressures

I have been having A/C problems. So I went and bought some gauges and have read lots of threads but Nobody ever mentions what pressures I should be looking for when I hook them up to the system. I hooked them up without the motor running and had 40 on the low side and 250 on the high side. it is supposed to be about 90 degrees outside today.
could someone tell me if these are in the ok range? Also do I need to test with the motor running? when compressor kicks on? I have been without A/c for a couple months now and would love to get it figured out?

Knowing the year of your Jeep might help. Anyway, your pressures should be equal or close,suction and discharge, if the compressor isnt engaged. your gauges should have markings for the correct static pressure on it, should be somewhere in the mid 80's if your system has liquid refrigerant in it, i think. sounds to me like you might have a restriction somewhere though.

Your profile shows you have a 99.

Pressures are measured with the engine running, compressor engaged. If you have 40/250 without the engine running you either have a serious problem or simply don't know how to use the gauges (sorry for being blunt).

As Quaboag says, with the engine off, both low and high sides should read the same and be approximately the ambient temp.

Saudade said:

Your profile shows you have a 99.

Pressures are measured with the engine running, compressor engaged. If you have 40/250 without the engine running you either have a serious problem or simply don't know how to use the gauges (sorry for being blunt).

As Quaboag says, with the engine off, both low and high sides should read the same and be approximately the ambient temp.

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after I made the thread I went back out and I am unsure if my gauges are good or if I know what I am doing. Thank you for answering what pressures should be with engine off. What pressures should I be looking for with the compressor engaged? I also wonder if I do have a restriction somewhere. I jumped my compressor and let it run for a minute without the gauges and then shut down my engine. I then felt the temp of each of the lines. All where very hot except the one going from the condenser to the evaporator. The dryer was also hot.

40 low, 250 high side pressures would be pretty ideal with the compressor engaged. There are a some variables though...ambient temp, engine rpm etc. i would think if the condenser or orifice are clogged, while you have the compressor running, your high side pressure would be very high. somewhere over 400 psi. could be somewhat dangerous to mess with if you are not sure what you're doing.:fuse:

Check out http://autoacrepairs.com/

Thank you for the website reference. That is what I tried for an hour looking on the internet for.