how often should this be done ???
i have a 1997 C180 where the AC is starting to act up...

When i start driving (cold motor) every now and then AC wont come on cold, i can swap to heat and it gets hot, but nothing cold when changing to Cold. If i stop the car for for gas or something, then AC all of a sudden is freeezing cold.. i can swap to heat and back and all works... Any idea guys ?? what could cause this...

check you A/C compressor and compressor clutch. Maybe the compressor or clutch or both is acting up. Btw- How is the feeling of the Air coming out? does it feel really cold or warm but cool enough but not cool enough for a 100 deg day?

__________________
2001 E55

2001 E320 Sedan

2001 Subaru Legacy

2006 SLK280

2016 Subaru Outback 3.6

it almost feels like the outside Air, but strange thing is that after fidling a bit with ac controlls inside car it works every now and then, and works perfect blowing realy cold... but today too.... it's not working on my way to work... hopefully it will work on my way home....

Anybody got a nice pic of how to check ac clutch and ac compressor ?
I'm kinda new to the whole AC part... my first car with it...

Sounds to me like your issue is not so much refrigeration as it is probably blend door flaps not working properly. Probably a vacuum leak or bad climate control actuator pod. I bet your compressor is still running when the air is blowing warm (you can check to see for yourself). What I would do is put a set of manifold gauges on the system and verify correct pressures and cycling before proceeding any further.

__________________
08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280

i'm kinda noobish when it comes to AC and vacum, it's my first merc, and my first car with AC :-) I got the haynes DIY manual for it, but it doesnt say to much about AC and faultfinding :-) It's kinda hot from middle of the "scroller" and all the way to hot, cant say i can feel any diff from middle to very hot, but on the "white" area it's a mix, but the "cold" feels just like the outside air... If i wanna check the AC comp how do i go around doing that... And i cant feel any diff with EC on or off running AC on cold air :-)

i've figured out that the "clutch" on the compressor doesnt work, belt runs with motor, but the compressor/ac unit doesnt run along it... (gone get a picture) anybody got a 1..2...3 on what and how to check out the diff sources for errors ??

To answer your original question, NEVER! You do NOT change refrigerant like you change oil. You can do more harm than good doing this.

Secondly, you need to start by connecting a set of manifold gauges and get your pressure readings. If the clutch is not engaging, there can be many reasons for it, but the most common is a low charge which causes the low pressure switch to interrupt the clutch circuit. This is by design to protect the system.

If the static pressure is about 85psi on both sides without the clutch engaged, then the low pressure switch should be happy and you can then move on to check the circuit otherwise.

Good luck,

thnks for all reply's so far, but as a noob in AC world i'm not sure where to messure so i've taken a few pic's :-)
Hope somebody here can help me name the Fig1,3 and 4 :-D
here comes Pic 1 with fig1 :-D

Is this the Low pressure ????

next picture, this is the center (Fig2) of the "pump" and should be spinning if cluch is enganged ???

Next is Fig3... if cluch should be in, should there be +12 on this blue wire ?? or is this for something else ???


last is Fig4 :-D what do i messure here ? high ??


Hope pic's verent too big :-D and happy for all help, going on vacation very soon and would love to have this fixed before i go, i've ordered a pressure gauge tool, aprox 30$ and should gimmi the readings i need but wont have it to tuesday... a guy at the local merc dealer said after 2 sec of checking say that the pressure looks ok :-) and ofcourse wants to spend 3 hours faultfinding on it at 175$an hour....

Hmm forgot fig 3 in first try, so i edited the post

I've got a reply that Fig 1 is low pressure, and Fig 4 is High...
I've had the heater on full and it's not hot air comming before I have the "wheel" all over on HOT and it "click's" at the very end of it. Compressor still doesnt turn, so cluch isnt engaging. All the way over on Cold it's not running eighter. The air between somewhat feals just like the "outside" air, it's maybe a touch hoter on the "hot" on the wheel and the "center" vent doesnt blow that much air eighter..

Any tips guys ??? Realy would love to have it fixed :-)

Is still TIP #1 that i'm running low on fluid ?? dont think it's been touched since car was new in 1997.... So maybe i just need a refilling..

I'm just thinking out loud in ignorance, but if the system needs re-charging wirh refrigerant, does't that mean he has a leak in the system? If so, then doesn't he have to isolate and fix the leak, replace the Dryer and vacuum test the system, before re-charging? Or am I wrong in my assumptions.

__________________
1984 300SD TURBO DIESEL

thats what i have figured out too, but some guy claimed that it's a loss of aprox 8% or something each year (not sure loss of what but) and that it might just need a refilling. The strange part is that it was woring on and off for a couple of days before it stoped working completly. I could start up in the morning head to work and AC didnt work, if i did a quick stop, turned engine off, and then when i started driving again AC worked perfect. It was like that for a couple of days/1week before it stoped working all in all. Now the compressor cluch doesnt "engange" att all and i have no AC :-( The aux fan (if thats the fan behind my radiator) is running when coolant is at aprox 85-90 deg Celsius (185-195 def F).. none of the "pipes" thick or thin get's hot or cold and there are ofcourse nothing happends in the "lookingglass" of the receiver-drier (if i got that right).

So i'm realy getting frustrated over this stuff....
I'm just waiting for a HOT tip on what to do next...

I'm not familar with your particular model, so I can't tell from the pictures. I can, however, trace the lines on any a/c system and tell which is high and which is low. You need to get an a/c book and do some reading on a/c fundamentals. Once you understand the principles you will have no trouble determining which is which.

I strongly suspect that your left picture is the high side and the right picture is the low. You can proceed safely on an R12 system by connecting your high side gauge to the one you suspect as the high side and start up the system, if the pressure goes up above 80 or 100 with the system running, then that is the high side. If not, connect the high side gauge to the other port and see if you have much lower pressure. You use the high side gauge for this test so that you don't peg a low side gauge, possibly damaging the gauge.

If the compressor is not kicking in, then it doesn't matter for your preliminary test because you will have the same pressure on both sides. If it is below about 83 or 84 psi, then the system is empty, actuating the low side cutout switch and that is why your clutch is not kicking in. That is the most likely scenario in the case where the clutch is not engaging.

Good luck,

I'm not familiar with non-North American vehicles - but I would guess that the 97 C-Class is R134 not R12 since the NA C-Classes (C230/280) of the era were mandated to be R134. If it is R134 then the hi/low side fittings are different sizes and you cannot connect the gauges wrong.

__________________
Daily Driver: 02 E430 4MATIC
In the family: '03 E500 // '04 ML500 // 64 220SE