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MB Paul
MB Paul, Mercedes Technician
Category: Mercedes
Satisfied Customers: 3567
Experience:  Qualified Mercedes Benz Diagnostic Technician - 20+ years experience - Workshop Foreman for Mercedes
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Air conditioning doesn't work, Started a couple of weeks

Customer Question

Air conditioning doesn't work
JA: How long has this been an issue? How many miles are on the car?
Customer: Started a couple of weeks ago. 75,000
JA: What is the model of your '75 Mercedes?
Customer: Its a 2000 S430
JA: Are you fixing your S430 yourself? What have you tried so far?
Customer: Recharged the A/C, service valve was leaking. Checked climate control codes from panel. Got a code 1053 and reset codes. Checked the senor data and the pressure in the system is 7.4 bar
JA: Anything else you want the mechanic to know before I connect you?
Customer: Checked all the fuses
Submitted: 10 months ago.
Category: Mercedes
Expert:  Michael Warfield replied 10 months ago.

So the system still does not work after recharging the system or it stopped working shortly after?

Customer: replied 10 months ago.
It still doesn't work after recharging. It appears that the compressor isn't coming on
Expert:  Michael Warfield replied 10 months ago.

And the fault code 1053, what type of scanner did you use to retrieve it? That could be a generic code in the engine computer, the real fault code lies in the AAC pushbutton module. That code needs to be cleared before the compressor turns on as a fail safe.

Customer: replied 10 months ago.
I got the code from the push button module. I then hit the left auto button, right auto button and the pushed in the right button and then the left and it says clearing or erasing
Expert:  Michael Warfield replied 10 months ago.

What type of scanner did you use to read the fault? Can it look at actual values? Does the code stay cleared or does it come back?

Customer: replied 10 months ago.
I only have a generic scantool. I got the code from the pushbutton screen, not a scantool. As soon as i clear from the screen and recheck it comes right back. The only data i can get is from the pushbotton screen. the main one I looked at was the pressure and it was 7.4 bar.
Expert:  Michael Warfield replied 10 months ago.

That fault code is for communication with the rear door control module, I think there must be low pressure in the system preventing compressor activation or the compressor bad. Can you access the A/C compressor connector? It is located on the top/outside and it just pulls out. We could do a voltage test there or we could lift up the fuse box and test some of the wiring in there but it would be harder because there are about 30 connectors under it.

Customer: replied 10 months ago.
I'll check the power at the compressor. Give me a little bit to get that done and I'll let you know the results.
Expert:  Michael Warfield replied 10 months ago.

Ok, I should be available all day.

Customer: replied 10 months ago.
Ok, I have power to the connector on the top of the compressor. The ground is good and connected to a nearby bolt. I took the cover off the front of the compressor and the bolt turns with the pulley with the compressor on or off. With the A/C turned on the high and low sides are both on 75 psi.
Expert:  Michael Warfield replied 10 months ago.

So if the compressor has power and it is not turning on, wouldn't you say the electromagnetic clutch could have an open circuit. It is not seized up but it's not applying any power.

Customer: replied 10 months ago.
Is the compressor clutch supposed to be engaged on the front all the time? The pulley and "hub" part with the bolt in the middle turn all the time whether there is power or no power.
Expert:  Michael Warfield replied 10 months ago.

Ok, then you don't have a magnetic clutch. Some of the 2003 models had variable displacement compressors. If you are getting some voltage, then it should be building pressure. The variable displacement plate be faulty. You wold need a diagnostic computer to see if there is a request for A/C but it sounds like there is a request because of the voltage there.

Customer: replied 10 months ago.
Should I check with a voltmeter to see exactly how much voltage is being sent to the compressor? Will that tell us anything?
Expert:  Michael Warfield replied 10 months ago.

Its a PWM signal, if there is some voltage, its getting a signal.

Expert:  Michael Warfield replied 10 months ago.

If you had a diag computer, you could actually see the amount of request. Because you have some voltage is there, it must be trying to actuate. Because you have no pressure, the compressor must be bad.

Customer: replied 10 months ago.
What would it do if I unplugged it and applied full voltage just to the compressor?
Expert:  Michael Warfield replied 10 months ago.

It doesn't work like that since it is not a magnetic clutch. It needs a pulse width modulated signal like a fuel injector to operate.