alloutmk23

Hi guys,

I'm hoping I could get some input from you before I decide to take my car to the dealer. I tried to switch over to AC for the first time this season and no cold air was coming out. Fully Lo, AC on and fan at full blast, blowing hard but no cold air at all.

When I turn on the system, if the fan is at a low speed I hear a hissing sound. IDK if this is normal? Also, when I popped the hood I notice that (picture attached) this small part ticks. I don't think that it ticked before...could be a temp regulator?

I still need to check the Freon but any help would be much appreciated. I only have 30k miles on the car and have never had any previous issues.

Thank you.

beejAMG

whilst all these are happening. was the car moving or stationary? my wife had the same problem before, since ours is a blueefficiency, ac wont engage until the car starts moving.

Live Oak

" I tried to switch over to AC"

That's a little puzzling. Generally, the AC runs all the time, winter and summer. Do you mean you didn't have it on Auto, and the AC never turned on? I wonder if being idle is bad for the compressor, etc?

beejAMG

Nope, not what i meant. I reckon that is another feature for the blueefficiency. Upon start up, you turn AC on and it will blow air, NOT cold air but, it wont start to get cold until the car starts to move. I guess its to save petrol or something.

Ausmbtech

The part your pointing to has nothing to do with the A/C, it's the purge valve for the fuel tank.

If you can hear hissing when the A/C is turned on then it sounds like the system need regassing. Don't run the A/C when the refrigerant is low as it will prematurely wear the A/C compressor.

alloutmk23

Thank you for all the help guys. The car was definitely in motion and when I say, "switch to AC" I mean put the temp on a low setting and making sure to push the AC button to illuminate.

I will not run the AC until I have the Freon checked. Hopefully that is the problem...I'll give you guys an update.

iGeorge

From some prior experience; I offer good news and bad. The hissing you hear from the center vents is normal; don't know what it does, but my past three Mercedes made that sound. The bad news is it sounds like your system lost its refrigerant, and instead of just replenishing it, you really want to find out what is leaking. My mechanic says a certain amount of refrigerant will migrate out of the system, but it would take years to deplete enough to keep the system from working. If you lost it all over the winter, odds are something leaked.

audiophilitis

agree with George -- if you're low on freon, there's likely a leak in the system.

Arrie

All A/C systems have a low pressure limit sensor. If the refrigerant is too low for the compressor to run safely this low pressure limit disables it. I would also think this car has a message displayed if this happens but not sure about it.


As the troubleshooting steps the first thing is to get a pressure gauge and measure the pressure on the low pressure side when the compressor is operating. Gauges like this are very low cost. The best ones are with an adjustable dial that you set to the ambient temperature. This with a bottle of refrigerant gets it going fast.


But this is simple stuff as you may find out that the compressor is running fine and pressure is at where it needs to be but still no cold out of vents. This would open a whole new can of worms as this would mean that the doors that mix the hot and cold air are not working correctly.