AC trouble. Supposed evaporator leak

[NickDech]

Last summer my ac crapped out. I got it refilled and it lasted a good few months before it was blowing hot air again. When I got it rechecked this summer, the shop said that the leak was coming from the evaporator behind the firewall.

Assuming my problem was a leak, I bought a at home recharge kit. When I took a measurement of the low side line, it was reading about 75psi when not running, but when it was running, the pressure would raise to 45 psi then the compressor would shut off, lowering the pressure to something like 10-15psi, then it would shoot back up and then down, etc...

Would a leak cause this or is this something different?

[NickDech]

After chaning my search keywords, I found a few postings about this same topic. Assuiming something is wrong with the evaporator because of the symptoms.. Is the evaporator leaking or is it blocked? If it is blocked, how can I unblock it. If it is leaking, how is this causing the pressure fluctuations and turning off the compressor?

Also, how would I empty out all the 134a in there?

Thanks

[YtseJam454]

It's cycling off because the pressure is dropping too low when the clutch engages. You most likely need more refrigerant. A high side reading would tell us for sure. I doubt the evaporator is blocked.

[NickDech]

Thanks. Do you know what the high side pressure should be, my manual is long gone?

[YtseJam454]

Well that depends on the state of charge, abient temperature, elevation etc, but I'd say when the compressor is running with the low side goin that low if you see 200 on the high side you're in trouble. If it's less you need more Refrigerant