The air conditioning is not working on my 1983 300SD. The problem intially traced to the low pressure switch no doubt from leakage over the years. I bridged (jumped) the switch to get the electromagnetic clutch to activate to enable the high and low pressures to be taken. I was unable to find in my MB manual what the pressures should be, could you please post guide lines for these values, (still using R12 and system is original). Thanks in advance.