No high side

I work at an apartment complex that was built in the early to mid 1960’s. My problem is that with this heatwave we have been having, all my compressors are siezing up, and none of the original units have a high side access port. without draining each unit and installing a valve, is there anyways to establish what my high side pressure is?

Saddle valve can tap an existing line without losing all of charge
Good luck

I’ve used a lot of these solder on access valves