Have an RPM-based droning/humming coming from one/both of the AC compressors. Maybe also the AC performance is not what it used to be. Trying to figure out AC refrigerant servicing. There are two easily accessible ports on each side of the radiator, but these must be the high-pressure ones because a R134a connector doesn't fit. The driver's side low-side port is also very accessible near the power steering reservoir, but the passenger side port is below the passenger side air intake and there's a tight fit with the coolant reservoir. Wondering any tricks to getting access to the passenger side port? Remove/loosen the coolant reservoir? Remove the passenger side air box intake? Flummoxed.

 

So in case anyone cares, I have an update. I purchased a can of A/C oil and a second can of R134a freon from Walmart and easily serviced the driver's side port. I stuck an A/C thermometer in the center vent and watched how cold the A/C got when set to LO (full cold setting). I alternately added oil and freon until the thermometer got close the 40 degree reading on the therm. It never made it to 40 degrees, but close enough. It's so easy to service this side, I will wait until it gets really hot here and service it again if needed.

Then I re-examined the situation on the passenger side (for the rear A/C unit). I was changing the engine air filter elements, so after I disassembled the airbox cover, I determined I could not move the intake tube out of the way, and I did not want to mess with the coolant reservoir either. So, I tried squeezing my hand past the air intake and the coolant reservoir and finally unscrewed the cap from the low side port. Then I was able to push the R134a fitting on the port and was able to service the rear unit.

I began by servicing the oil because of the humming I was experiencing. I figured maybe the oil in the system was low. By the time I got the new oil added, the temperature was already at 40 degrees, so I did not even service the freon for the back unit.

Then after reassembling everything, I went for a drive to see if the humming had eased any. I believe it did get better, but still has some RPM sensitive humming/drone. Maybe that's just the way the car's supposed to be. I have always had this noise since owning 8 years and only started to worry about servicing it after the A/C performance (getting cold) seemed to diminish.

In the end, I am happy with my effort and now have learned a new skill. First time I ever serviced an A/C unit in any vehicle in my 50 years of driving!

 

Glad to hear it worked out OK! Not many Maybach owners let alone ones who will do a DIY! Always good to see more of these threads posted!