lei

04 E320 wagon.

Freon low, A/C off switch blink and then on. How can refrigerant be charged ?

It seems that the compressor needs to be running in order for refrigerant be drawn into the system through the low pressure side. However, the A/C off light on means compressor is not engaged, right ? How to force the compressor to be engaged ? or is there any other way to charge the system ?

vettdvr

The compressor has no clutch and runs full time. At least from what I understand of the design. There is an expansion valve and lack of freon will cause the light to come on in the system.

I have rebuilt many US systems but never the MB. I haven't checked on how to add as mine hasn't failed yet.

There should be a low (large diameter) pressure line with a freon connector. This is where you will add freon. But I HIGHLY recommend you measure the HIGH side (small line w/ connector) to insure you don't overfill/pressure the system. (Note there are very specific pressures you will want to attain.)

If you have never worked on a/c before you might consider having the system serviced before you attempt to do any work.

paulv

In addition to vettdvr's recommendations, the AC system is a "closed" system so if the refrigerant is low, then it has leaked out of the system. Need to find the leak and fix it before recharging the system. You can buy the cans of refrigerant that have a UV dye so when you add the new stuff, you can check for leaks with a UV light (inexpensive lights can be found at auto parts stores). After you fix the leak, add more refrigerant and watch the high-side pressure as vettdvr discussed. Do not use the refrigerants that have leak sealer in them as they tend to clog up various orifices in the system (and then you have another problem). Good luck.

Regards,
paul...

lei

Thank you, vettdvr and paulv.

If the compressor is all-time engaged, what does that A/C Off switch for ? Does that also mean fuel consumtion and rozen evaporator in the winter ?

Both high and low connectors are very easy to access. Where can I find the high presure specs ?

Will do the UV light trick too.

vettdvr

The switch powers the blowers dampers temp controls.

No you don't get a frozen anything in winter due to variable displacement compressor and expansion valve controls.

Do a search for freon pressures for the type freon your system has and you will find the temp chart/pressure relationships.

I suggest you look for your leak ref. Paul, unless your system has never had freon added.

SZMB

If the freon is way too low, the safe mode feature in modern MB does not allow you to turn on the AC until the system is recharged w/ freon, R134. When you buy one of those $15-$20 R134 cans from an auto store, it comes with a pressure gauge. Just connect it and measure the pressure while the car is running. Recharge it and that should get you going for while. If pressure is low, there's a leak and needs to be fixed, so you don't have to recharge it regularly...besides bad for the environment anyway. There was a leak in my 2004 E500, I just had it fixed at a MB indy shop for $200, including the gasket seal, labor and recharging.

platinumblue

lei............

Back in early 2003 I noted a recall on the E 320 air conditioing unit leaking. My Vin show this recall was performed on my E-320. So I suggest you contact the dealership first. If you need additional information on the campaign # let me know. Also when checking AC system with manifold guages Vette is correct about measuring presuures on high and low side ports. Also ambient temperature is key to know the amount of freon to replace I can help with this if you decide to go this route. Send a private message for additional details.

Platinumblue.

lei

Thank you all, for the useful information. I will measure the pressure first as suggested. Meanwhile, a dealer visit was schedule in about 10 days.