Air Conditioning 126 Series

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.

[VA300SD]

Older 300SD's will eventually spring a slow leak in the system. It's amazing that they do work without any problems for 15-20 years. The A/C in my 81 SD was "rebuilt" a month ago at the dealer's recommendation after they discovered a leak, and they will not just recharge with R-12.
After various valves, gaskets, and new evaporator? (the small cylinder thingamajig mounted on the wheel well) and new oil (?) plus recharge of R-12 brought the system back to new condition. Well worth the $500 they charged - Although I love tinkering, did not want to mess with it and risk not doing a thorough job.
The dealer mentioned in most cars they just refurbish and refill with R-12.
If the compressor is shot, then they recommend converting to R-134.

[Benzmac]

The pressures when full of freon at about 80 degrees F. Low=about30 to 40
High=about 225 to 250

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Benzmac:
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

Thanks Benzmac.