Air Conditioning Cooling System on 2006 Mercedes-Benz E350

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When I try to turn my A/C on the light blinks for about 5 seconds and then turns off. I take this to mean that my r134 is low and I should refill. Can anyone verify this for me.
Second question is where is my low pressure intake valve for the r134 coolant? thx
(1) Answer
When you get a flashing display LED, it usually means you have a fault and the system has been shut down until the problem has been corrected. If you did charge it, it may still not work without clearing of the fault code.. The low side port is usually at the left side of the engine compartment or it could be on the hose manifold at the rear of the AC compressor. Before working on the vehicle, look at all the AC hoses and other components for traces of oil on them, if you find oil, you may have to fix a leak first before you recharge the AC system. Good luck.