If your boyfriend had aguges which it sounds like he has, connect the gauges after the car has not been running for a while, ie overnight. The high and low side pressures will have equalised and with R134a refridgerant the static pressure will be approximately the same as the ambient temperature.

ie if its 80 degrees outside the high and lowside ppress guages should read about 80 psi.

If you look up a temperature and pressure chart you will get the exact value but this is approximate enough to determine if its high or low on refridgerant.

Pete