I’m attempting to get the A/C working on my car. The initial issue was that the compressor would only kick on for a few seconds and the pressure would drop to like 15 psi and then kick back off. So I figured that just meant I was low on charge, so I got it charged up but now I have a new issue. The compressor will stay on for 10-15 seconds and the pressure will read around 25psi, and the air inside will get cold. Then the radiator fan kicks on, and the pressure will drop below 20 and the compressor will kick off. Is this still a charge issue, or is something else going on?
What’s the pressure on the high side?
Tester
I’ve only got a cheap Walmart gauge that connects to the low side. 
Then, that’s the problem.
Tester
I believe this has a cycling clutch system . . . meaning if the ac is on, the compressor clutch won’t stay continuously engaged
You really need to have a gauge on both high and low at idle and report the readings to us
Here’s what we need . . .
high side with compressor engaged
high side with compressor disengaged
low side with compressor engaged
low side with compressor disengaged
I’ll try to get my hands on a set of gauges and report back.
The system capacity is 34 ounces, how much refrigerant did you add?
If the suction line is cold with the blower on high there is a sufficient charge in the system. It is normal for the clutch to cycle if the weather is not terribly hot.