98 C280 AC blowing hot air

[clankford]

Ok, I have been absent from the forums for awhile, so bear with me.

I have a 1998 C280. It has been sitting for about 2 months. All was well when it was last run. Now, the AC is blowing hot air. The compressor is cutting on and off as it should (by manually changing the temp selector up and down). I have hooked up my gauge to the low side only. It is measuring about 36 lbs when the compressor is on and about 90 lbs when it is off. I will do the dash diagnostics for more info. Thoughts guys?

kid

-LATER-
I ran the "actual value codes" and here they are:

01 82
02 82
03 90
05 82
06 161
07 01'4
08 91
09 50'F
10 275
20 270
21 070
22 0
23 0
24 13.9
40 02
41 03
42 18
43 6-C
50 84'F
51 72'F
52 50'F
54 OFF

[pmizell]

07 01'4

1.4 bar low side pressure sticks out. I recently had the exact same problem where my C280 sat for a couple of months and the AC acted exactly as you describe, including the compressor cycling. I added a can of 134a and the AC has never blown colder, with the charge holding tight.

Most here would suggest you have it professionally leak checked and recharged, so the choice is yours.

The evap temp sensor seems to check out as it matches your outside and inside temp sensors.

Good Luck

[clankford]

Originally Posted by pmizell

07 01'4

1.4 bar low side pressure sticks out.

What should it show?

kid

[TMAllison]

Its a variable pressure system.

As stated above, is prob low on refrig and best practice is to evacuate and install new/known fill amount; not everyone does that.

[pmizell]

For a pure reference standpoint, in AC diagnostic mode, the low side reading in my '98 C280 fluctuated between 10 and 16 bars idling at operating temp. (just checked) My evap temp read 39F. The ambient temperature here in Houston is 84F.

Hope that helps and Good Luck

[clankford]

Thanks pmizell! I will take a look at it tomorrow. I'll hook the gauges/hoses up and see if I can get it going. Thanks very much for going to the trouble to check your codes for me. That will definitely help!

kid

Originally Posted by pmizell

For a pure reference standpoint, in AC diagnostic mode, the low side reading in my '98 C280 fluctuated between 10 and 16 bars idling at operating temp. (just checked) My evap temp read 39F. The ambient temperature here in Houston is 84F.

Hope that helps and Good Luck

[georgeb]

I would at a minimum, evacuate the system and put a vacuum on it to see if it holds. I think its silly just to add refrigerant because you have no idea how much is in the system, and if there is a leak you will just be wasting time and money.