I recently replaced my leaky evaporator, and while doing so also checked the orifice screen while the system was open (since the previous owner blew out the old one and there was shrapnel floating around). When I pulled it out, the orifice came out in two pieces, including a little spring. I was prepared to buy a new one, but no one had any in stock, and the two pieces seemed to pop back together. So I looked at some photos online, got the spring in the right place, and it all seemed to jive, so I figured it'd be worth a try.
I've never done A/C work in the winter, nor have a made note of how frequently the compressor cycles in cold weather. After I put everything back together, evacuated the system, it held a vacuum, and put 2 12 oz cans in (I believe my TJ's capacity is ~20oz) it was still constantly cycling on for 10 seconds, off for 5. On the last can I messed up and lost a bit, so I thought maybe I didn't have enough. So I put a third (!) can in, and it still acts like it's low on refrigerant.
Right now this is what I'm getting:
Low side (engine off, equalized): 60psi
Low side (compressor running): off at 30psi, on at 40psi, endless cycling
High side (compressor running): 100psi increasing to about 140psi, then it drops to 100psi again, and then maybe 1 second later the low side switch kicks in
When I jump the low switch it stays running constantly at about 25psi lowside and 100psi highside.
I can't figure out what's going on. I did some research and concluded the orifice was screwed up, since the low side is dropping so fast. It made sense that the compressor was sucking out all the 134a and cramming it into the condenser, where it was trapped by a broken orifice. HOWEVER now that I put the gauges on it, the fact that the high side is normal (ambient*2 +50) makes me think that isn't the case.
What I'd like to know is, at 45-55f how often should a healthy system be cycling? Is the problem the low pressure switch and not the orifice? Is this all normal for cold weather?
I am grateful for any help from you Jeep geniuses.