I have a 2000 S430 with an A/C problem. The previous owner had problems with the A/C cooling the same on both sides. Now the A/C does not work at all. It seems to be stuck in the econ mode. Looking at past repair records the dealer has checked the freon, replaced the sun sensor, evap temp sensor and a relay. Each time it seemed to fix the problem but now the A/C does not work.

The control panel which says A/C on shows a red light. I had the freon checked and they said it is ok. When I put the gauges on it both sides read the same. What is the correct reading for the high and low side? Any ideas as to the problem?

I am fighting a similar problem with my 2002 S500. It seems that when the AAC (CCU) senses something wrong it locks out the A/C and turns on the AC OFF light. It won't attempt to function again until the code is reset using the diagnostic computer that a dealer or MB shop will have.

You will have to get someone to read the codes, reset it, and go from there...

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02 S500
92 500SL
92 400E (Sold)
87 300E (Sold)
83 300D Turbo (Sold)
75 300D (Sold)
74 240D (Sold after 20 years)

Can't you extract the codes from the pushbutton unit, as on the E class?

The S-Class climate control system uses the evaporator temperature sensor as a means to detect low refrigerant level. If the sensor is reading incorrectly, but plausibly, it can shut the A/C compressor off without storing any fault codes. To put it simply, the AAC control unit thinks the system is low on freon.

Assuming the system is correctly charged, you'll need an SDS to fix the problem. The programming in either the Electronic Ignition Switch (EIS), or the AAC module needs to be changed. The coding option "Refrigerant Level Check" should be set to NOT ACTIVE.

Is the evap temp sensor something I could change? If so where is it located and would I still have to take it to a shop and have the SDS used? I have worked on domestic cars for years but never a Benz. Thanks for your help.

Coybenz,

Someone like ILUVMILS will have to answer regarding the location, but it is apparently easy to reach because my shop has replaced my ETS twice for me while I waited. From looking at the old part it just inserts in a slot and clicks in place. I think you will still need to get the code reset in the AAC control unit.


ILUVMILS,

I don't want to hijack Coybenz' thread, but we seem to both be fighting the same issue. I took a printout of your recent post about changing the "REFREIGERANT LEVEL CHECK" option to "NOT ACTIVE" to my shop this afternoon. They tell me that they already changed this setting to no avail before replacing the AAC control for having a fault (A/C OFF) with no code stored. They added that the new AAC no longer has this setting as an option. The jury is still out for me, but it seems that after replacing the AAC the problem will clear without having to have the unit reset.

We have replaced the AAC, replaced the pressure switch, drained and recharged the refrigerant, and now replaced the ETS a second time. It is working fine at the moment, but it has been quite intermittent.

Does this seem reasonable, or have they overlooked something? I changed from AAC #220 830 09 85 to #220 830 11 85 with the newer programming.

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02 S500
92 500SL
92 400E (Sold)
87 300E (Sold)
83 300D Turbo (Sold)
75 300D (Sold)
74 240D (Sold after 20 years)

Speace, how expensive is it to replace the AAC?

The AAC is an $800 part at list price. I negotiated a deal with my independent shop to sell it to me for $600 since we were taking a chance on it not actually being my problem. I essentially bought it from him at his cost. the AAC is also simple to swap out, but I don't know if it needed any programming to activate it.

The ETS sensor was about $50.

__________________
02 S500
92 500SL
92 400E (Sold)
87 300E (Sold)
83 300D Turbo (Sold)
75 300D (Sold)
74 240D (Sold after 20 years)

Speace, thanks for the information.