If you want to measure the health of your A/C, you need to compute the sub-cooling temperature (superheat for fixed orifice A/C, but the mk3 uses a TXV so superheat is always correct).
To do that you will need a manifold gauge set and a precision thermocouple. You will also need a sub-cooling chart for R12, which can be found on the net.
To do that you will need a manifold gauge set and a precision thermocouple. You will also need a sub-cooling chart for R12, which can be found on the net.