takkie

Hello,

i have a 2009 ML350 4Matic, with 44k miles.

I had a lower cooler line leak in April, and i took it to dealership to get it replaced. this was done, and i dont see any leaks anymore (it was slow slow drip onto the plastic pan)

The AC has been working fine all along, and last month, i turn on the AC, and i noticed that the air coming out is just fan air rather than cold AC air (sorry - i dont know whats the right word for it). It was a short drive, and i ignored it.

Then the AC has been working without issues for a month.

Last week, it was a longer drive to the zoo with the kids, and it was a hot day, i turn on the AC, and only fan air is coming out rather than cold air. I drove for half a mile, and stopped at the side of road, turn off the car , start up the car again, still fan air. Drove for 5 minutes more, cold air started coming out.

After this, AC has been working fine, with cold air.

This morning, i turn on AC, again, fan air. It was a short drive, so i parked the car and run my errands.. when i got back to the car and head home -- AC is working again with cold air.

What would leak to this random cold/fan air please?

My car is out of warranty and when it was still under warranty, i had replaced the blower about 2 years ago, becuase one time, no heat/cold air would come out.

Thanks in advance.

takkie

Anyone pls?

takkie

hi.

so it happened again yesterday and this morning. I have tried various things and i believe it is a electrical issue rather than mechanical?

I noticed that, when there is no cold air, i leave the setting to AC On + Auto, then turn off and turn the car back on -- there will be AC Cold air.

The AC air button does lit on / off when i press it.

BUT i noticed that the AC OFF/ON button, eventho that it does lit up/off, but it has no effect while i am driving. If i leave the AC OFF (light off), the air is still ice cold.

I also tried that, when the car has no AC air, i turn off the climate control system, or turning AC off then On, has no effect, there is still no AC Air.

So i think, if the car was started with AUTO + AC on, the cold air will be there.

Is there some relay or fuse that i could easily replaced and try this? becuase i think if there are low on refrigerant (Which based on what i ready on internet, it should not happen becuase its a closed system. If refrigerant is low, that means there is a leak), i dont think i can get AC at all.

But the fact that sometimes it has, sometimes it doesnt, leads me to think its electrical somehow not triggering/enabling the AC to kick in.

please advise, much appreciated.

takkie

come on , guys... anyone?

jsmith18

I have had this happen on cars other than Mercedes and what would happen is the moisture in the air would freeze on the condenser and block the airflow preventing cool the air into the cabin. The problem was the temp.sensor was not working correctly and would allow the condenser to get too cold. Eventually it would plug up with ice. It eventually melts and everything is then fine although sometimes when it starts to work again you get a damp smell. Happens to my window AC too if I have it on too cold. Just a thought.

takkie

is the temp sensor the same as the climate control system internally?

I am starting to lean towards its the climate control setting not functioning. I have tried to turn on AC and i know the motor fan turns on. When i turn off the entire AC system, the fan stops. BUT when i turn on the system without AC on, the fan still runs and cold air continues to come up. (Is it suppose to run when system is on but AC off?)

One thing is, when i have the system on, but regardless AC is on or off -- cold air just continues to come out. Its like i have no way to not use the AC once the system is on.

And also -- since i had the cooler line replaced, is it possible that the AC Compressor is freezing due to the cooler line change? I am not quite sure what the cooler line do, but i know it ocnnects into the radiator so i am guessing its AC related.

Thanks.

06e320cdi

I know on my 08, even if the AC switch is off, but rest of system is in Automatic, it will blow cold air. Until it cools the ventilation system, then it will just blow outside air. I was thinking this was a function of the system removing excess heat/humidity from the cabin.

N_Jay

Since it does not work sometimes right off the start, I would doubt it is freezing up.


Sounds like an intermittent problem causing the compressor not to turn on.


I would start with having a GOOD AC shop (not the corner garage, Firestone, or Midas) check the refrigerant level as if they are a little low they do not turn on, and if you are right on the line it could be intermittent.


After that I would first suspect the AC control unit (because our darn MBs are too darn computerized), then maybe a loose connection somewhere.

takkie

thanks.

does anyone know if the "Lower Cooler Line" into the radiator is use to transfer refrigerant? I am still trying to see if its the dealer messed this up when they replace the lower cooler line so i can go back and complain and make them check for me , for free.

Thanks.

LuisGese

I had this problem a couple of times. I thought its some kind of System cleaning.....

Carcollctor

Does your AC compressor have oil or Power steering fluid leaking on top of it?

I've had problems with the plug that goes into the compressor I replaced my daughter's compressor with one covered in ps fluid and dirt. I didn't clean the plug out good enough and we had that issue. We had to turn the car off and on intermittently after a start.

When cleaning it I noticed the clip was cracked so be I ended up electrical taping the plug tight and to keep out dirt.

DATL

My 2009 ML350 4matic AC usually blows ice cold. Saturday it just blew hot air. Figured Freon just needed recharging as it's never been. Went to a local oil change place to have it checked and they said compressor looked a little worn but ok and Freon levels looked ok. They assumed it was an electronic issue or issue with the controls and they couldn't fix.

Took it to an import shop (Mercedes dealership never called me back). They diagnosed that the compressor and blower were bad. Metal shavings in blower. $2,100 bill but CarShield warranty covered most. Forgot I had it. Planned on canceling it. Probably should still lol. Plus side AC is ice cold again.