A couple of problems with that -- first, the outside temperature is in the low sixties F, which means that the system is barely working. That contributes to short cycle time. The pressures will look a lot different with the air temp at 90.

Second, static pressure isn't a good gauge of charge. The only useful pressure is really the high side (with a low side reading also).

Third, the low side-only reading, is not accurate in diagnosing the charge level, since the low side will respond directly to the cabin air temperature. Unless the system is almost empty and barely cycles on at all, the low side reading doesn't do a whole lot. Unfortunately Volvo and a lot of other automakers, stopped putting high side ports in their A/C systems. They've gone to charge-by-weight systems, which are fine unless they're the type that fizz refrigerant from evaporators. Or any other place.

It COULD be low on charge, but there is not much way of telling until you can measure vent temp and see what the output is in higher ambient temperatures.
--
Chris Herbst, near Chicago.

The cycling behavior is the classic symptom of low freon. It is not possible to say that the low pressure reading has a "standard" value, since it varies as a function of other system parameters (temperatures, etc.). It should only be used as a rough diagnostic. The only way to positively know if you have the right amount of freon is to evacuate and recharge with a measured *weight* of R-134a.

I would suggest that you add a small amount of R-134a and see if the cycling stops. If so, you probably have an evaporator leak.

Gerald C