1998 C230 ac recharge question
 

Can anyone tell me where the high end and low end valves are for draining/filling the ac w/ r-134 refrigerant ??? My a/c is working fine but has not been charged in 3 years. I have spotted a female valve behind the power steering fluid box which appears to be the high end one. Any tips or special tools needed ? Thanks. I have heard i need to charge from the low end valve.

If there are no leaks and pressure and operation is normal, I would not think that it would necessitate a recharge after only 3 years.

These are sealed systems, and unless it's leaking, don't "top it off." There is no need. Many MB's will go 10 years, or longer, without needing coolant for the AC system.

If the system loses coolant (R134A) then you'll probably have to track down a leak and fix it.

Leave it alone now.

yes, A/C system is sealed. Unless the system is leaking, I don't think so the A/C needs to refill the freon. If really leaking, find out where it leaks and fix it before refill freon.