Onericali

Hi. I haven't had AC for over a year now (I live in south Louisiana) and I'm really serious about making steps to fix it without paying the 2400 bs I was quoted.

My question is: If my pressure readings change when I turn the AC on, does that mean that the AC compressor is actually turning on?

Or does it just mean that the fan is possibly changing the readings?\

For example, if I close the doors to the car, the pressure will change.

I'm guessing it does not mean the compressor is turning.

Also, how do I get to the compressor to see if it is coming on visually?

I've already got a lot of console stuff out trying to repair my footwell flap stepper motor linkage.

Please help...

Onericali

Right now the temperature is 79 degrees.

With the car, ac, and fan off,

The low pressure is 85.
The high pressure when I open the valve is 95.

When I turn it on, the low pressure goes to 95.
The high pressure when I open the valve is still 95.

The high pressure is definitely low. The low pressure seems to be high.

This means the compressor isn't compressing much.

Now, isn't it possible that something is clogged, and that it isn't necessarily a weak compressor???

Also, are these readings even accurate? Why is the low side pressure going up with the AC running anyway?

Isn't it possible that the compressor isn't even coming on at all?????

Onericali

Nevermind. I'm pretty sure the compressor isn't running, and that I am just seeing a "base system charge pressure reading, which is meaningless."

All this work has been for nothing.

Is there any way to actually test the sensor readings or functionability?

This is a C230 so i can't just hit auto then hold down rest for 5 seconds. I don't have a digital display.

If I can simply find if one is not working, that will be an easy answer.

Otherwise, I have to get a multimeter, to test the compressor for various shorts, OR

I have to get lucky and find a leak, then either hope I don't screw up the oil/ refrigerant mixture,

or have it all vaccuumed out and reapplied.

Sigh..

Onericali

Okay I'm pretty sure there was a slow leak, then the compressor stopped turning on, and then eventually the pressure in the system evened out, which gave a high low reading and a low high reading, both showing about the same reading.

So it comes down to either doing a half *** job or a good job. The good job is this:

1) Vacuum out refrig

2) Take out compressor, flush and fill with proper amount of oil

3) Charge system

4) Find leak fix leak (not sure where in the process the best time to do this is)

Thanks for the help everyone. Or I guess, your welcome for anyone that learns from this and finds it some day.

Glyn M Ruck

If I was in your shoes I would take the car to an Indy HVAC specialist. Just explain to him that Benz have a system pressure/temp sensor at the base of the condenser that will not allow the compressor to run unless the system is fully pressurised - many are confused by this & think the controller has failed when the problem is insufficient refrigerant. This is to protect the compressor & many don't know this. The compressor is a clutchless swash plate unit & the swash plate actuator cannot be observed externally. As long as a good refrigeration guy understands this they should be able to diagnose the problem cheaply leaks & all. They have the gear. The real cost involved will be dependent on what they find with worst case scenario being a compressor replacement. That's when it starts to get expensive.

Good luck!

EDIT: As I'm sure you are aware the basic layout is as follows:









3 is the evaporator

4 is the heater radiator/heat exchanger

amanonfire

Glyn,

The AC light has been stuck on my climate control unit for a long time, thus indicating a problem with the AC and that its been disabled. Is there anyway to determine what fault it is registering?

Thanks.

Glyn M Ruck

Your W203 is older like mine where light on means A/C off - Yes?

If so and the light is on but the aircon does not operate you likely have low refrigerant pressure. Recharge the system & it will likely come to life. You can't diagnose anything on these aircons without system pressure at spec. Even to find a leak you obviously need to charge the system.

Onericali

Thanks a lot Glyn.

Great idea.

Once there, they can probably open up the compressor and take a look as well.

Should be good in no time.

amanonfire

Yes, light on is AC off.

My AC was dismal at best, so I used a recharge kit from Walmart. I know the risks of contaminating the system, yet live in an area where AC is only used at best 2 months a year so I wasn't willing to shell out to fix it properly. I charged the system and it came back to life, cold air, life was good last summer. Over the winter the AC off light has come on and stayed on, so I figured I had a leak. I put the recharge kit back on and got the proper pressure on the low port so I figured something else was very wrong and gave up all hope for a quick fix.

Thus this thread is interesting that pressure can be correct at the low port, yet wrong at the high port and still cause issues.

Onericali

I've actually seen A LOT of threads about the acEC/rest light on.

I don't have any off hand because it didn't happen to me.

Also make sure to run the AC once a month.

Best of luck bud.