My A/C doesn't get as cold as it used to. I know that it can only get so cold when it's hot out, but is there a way to add R134 (or whatever it is) to the system? How involved is it? I am talking about the C280, so hopefully it doesn't involve taking out the dash!!
It's not bad, just not working as well as it should.

If it's not performing as well as it did you most likely have a leak. You should recharge the system and check for leaks. The evaps are the most common failure. Hope it's not the evap because yours is also under the dash. Not as bad as the 140s, but still a lot of labor $$$.

Vinamg

David:
Behind the driver's side headlight there is a small black metal AC fitting that has a little round window in the top where you can see Freon circularing. I am not sure where it is located on yours. One sign of a leak and low freon levels is iff you see bubbles through this window when the AC is turned on. Good luck!

a/c coolant level
 

According to the MB service manual, the proper coolant (R134a) level should show some bubbles at start up and then go away (as viewed thru the sight glass) on a normal (70 deg) day. On a *VERY* hot day, you may still see some bubbles.

Overfilling is a great way to make your A/C work poorly!

Here's what I said (assume the a/c is running):
1) bubbles in the sight glass does NOT mean that the a/c is low on 'freon';
2) NO bubbles in the sight glass does not mean that the a/c is correctly filled.

What does that mean? There's only ONE way to be sure that the 'freon' level is correct; you must evacuate the system, and then recharge it to the proper amount specified for that a/c system. Other than that, using the sight glass is only a guess which can be very wrong!

[Edited by JimF on 04-26-2001 at 02:41 AM]

My post may not have been very clear: I did not mean bubles when (FIRST) turned on, I meant bubbles when the air conditioner is turned on (and running), as opposed to turned off (not running). At least, this is what my tech told me to look for before I had him fix the slow leak in my r12 system and convert it to r134a.

Well it's still cold. Is it possible that's it's just low on the fluid? Is that bubble chamber in the same place on my car? Thanks for help John. And keep in touch, we have to plan something soon!!

David, get a good A/C tech to check the pressures in the system. Have the center outlet temp checked. There are specs for all of these parameters. This is easy inexpensive stuff to get done. I would never recommend just throwing a little more refrigerant in because it's not quite as cold as it used to be. There are a number of sensors, switches, etc, that can produce that symptom. If you overfill, well you know.. :confused:

...and besides that: as soon as the system is too low on refrigerant the airco wouldn't even start getting cold anymore. As soon as the airco is activated you get a constant low temperature that gets mixed with air from the outside.
Setting a lower temperature means less air from outside, setting a higher temperature means more air from outside; the vented air inside the car is a mixture.
A lower temperature setting does not mean that the airco gets colder; the temperature that is generated by the airco is constant...

greetingz,

can anyone tell me what the air temp coming out of the center dash vents should be when the temp dial is at min.
1985 300D converted to R134 and a 1995 E320 with R134.
thanks,
Jim

This is a generalization.
If the a/c is just OK, but not up to par and the temp gage is running a little high, check this:
If the sight glass looks decent[almost clear] , check for aux fan turning on. If you are slightly low on freon, the fan will not come on because it is activated by the high side pressure switch at the drier/reciever. If the fan runs when jumpered at this sw., then the fan circuit [relay,fuse, etc.] are ok. So , we have a bad switch/or too low trip pressure.[ possible low freon].
Both these will result in poor cooling. And the aux fan not coming on will also add to the high temp on the cabin gage. [ no air flow through a/c condenser and Radiator.]
Don't confuse the a/c condenser fan with the aux fan that comes on at extreme coolant temps, for that is another circuit. [ usually at a higher speed].
That fan will come on without a/c controls being on and its function is controling engine coolant temps.

MB Spec
 

The data I have for my car says temp should be 6 deg C (43 F) at center vent w/ min temp control setting.

Measured it at (get this) 2 C (35 F) at coldest and 4 C (39 F) at warmest!

Does anyone know where that little freon glass is on my 1995 C280?

Jim,
Did you check the temp with your own thermometer? Or did you use your climate control (N22) read-out values?
I should do this.
Did you do this when your car was at 85 (+/-) degrees C?

A/C Specs per MB
 

Here's the specs that MB says should happen with a properly charged and operating A/C system for my car (C140).

The temp is set of "LO" (my car) and not recirculating inside air. Also used an external (accurate) temperature probe that was inserted into the center vent. The outside temp was close to 70F.

This data is from MB and this is what you should see at 40% and 80% RH (relative humidity). Also engine sb at 2000prm.

Outside ----- 40% RH---------80% RH
Temp -------A/C_Temp --- A/C_Temp
20-24----------5--------------------6-7
24-27----------6--------------------7-10
27-30----------6-8-----------------10-13

So for 21C (70F), you should see 5-6C (42 F) air coming out at RH of about 40 to 80%.

[Edited by JimF on 05-04-2001 at 10:41 AM]

Re: A/C Specs per MB
 

Jim, I don't fully understand.
What is the Temp on the left column? Is that the engine temp? What is RH %40 and %80?

I can figure this out if I know what the engine temperature, outside temperature, and supposed temperature of the AC (42 F) are to make the AC the 42F. But what are they? Maybe it's in that graph, but I just don't see it?! Thanks Jim.

The figures at the left are the ambient air temp (outside temp in celsius) David.

Example, today we had 90+F here. I had the thermometer in the center vent while parked at work. When I got in, the thermometer read 125F. Windows down, A/C blowing high - max cold, within 5 minutes the thermometer was showing 40F at center vents, dropped to 38F by the time I got home (still with the driver's window down - my favorite way to ride :)).

You can pick up an accurate A/C thermometer at your local parts shop. I got mine for something like $5.00. Registers from 0F to 220F.

[Edited by MikeTangas on 05-04-2001 at 02:09 AM]