Hi my AC won't turn on it flashes few times. I have fault code of 9ed187 which is temperature humidity sensor. Does anyone know where it is located?

 

when you get a chance, complete your model information - there are quite a few different "facelift" models around the world.
Flashing A/C button = low on refrigerant usually. No A/C light = very low/no refrigerant usually. Check with a gauge on the low side what psi is with engine and A/C running. I may be corrected here, but a low refrigerant will not produce a fault code. Your fault code is a separate issue.
Going back to the initial statement, with more vehicle information: exact year, engine, fuel type, doors, mileage.... the more likely a Member with your exact vehicle can assist. glw solution.

 

The flashing usually means Low Refrigerant. The larger A/C hose should be cold, the smaller one Hot. If the compressor is not engaging--it could be low blow refrigerant, or it can be something else not allowing it to come on. You need to check power to the clutch supply. If no voltage check other relays in the circuit. If the clutch is engaged but both lines are warm/hot, no refrigerant.
I suggest having a good A/C shop diagnose the issue. Do not just 'throw parts' at it.

 

Isn't this sensor located on passenger footwell cover... check if it is still connected or pulled a part during last service -

To diagnose further, look at your scanner live data for system pressure and bad/missing reported temperatures.
See if you can spot any value standing out as obviously wrong.

There are half a dozen Temp sensors in this HVAC system, including a networked sensor inside the OCP and one near ignition switch EIS that get plugged up by dust.

 

one near ignition switch EIS .......where the location ya

 

This may be strange to some.....this is a recent problem, with our 2012 ML 350 W166 diesel.....may be the same with others, our A/C would either come on for short bursts, then stop working, and the A/C rest button would flash. Took it into our favourite European mechanic shop which specializes in Audi,Merc,VW, etc. vehicles. They have gained my trust, and are extremely good at what they do. After diagnosing the car, it was determined that the compressor was shot, and not engaging. Replaced it, flushed and recharged the system.....no signal to the compressor to bring it on. I trust their judgement, and after a few hours of trying to make it work (at no extra cost to me) it was determined it may be the heat/cooling control cluster on the dash, so pulled the cluster out of another vehicle, same vintage and model that IS working, it just slides in and out like a cassette, same issue. Hmmmmm....they had about 10 hours into the car, and said....it's GOTTA be a wiring issue, it could be anywhere. At that point I said "it's ok" you've spent enough time on it at your own cost, just leave it. I sat in the car, spoke to it with an elevated voice, and drove home. With the car sitting parked, I started fiddling...I've owned more than one MB, starting back to the 80's, and this is weird. I push the ZONE button, light comes ON.....I push the A/C REST button, it flashes a few times, then goes OUT!! GRRRRRRRrrrrrrr.....I push the air directional button, and it shows that the Dash,Mid,and LOWER air flow are ALL on. I cycle through the combos until ONLY the MID and LOWER fan directionals are ON, and the front windshield air flow is shut OFF......suddenly, the A/C fires up, the revs, speed up a little, the compressor is ON, and NOW I have A/C. What the HE11??....I drive all day long, and the A/C works. My wife does the same the next day, and the A/C is working without fail....guess what??...because I don't know...try it!! Let me know....