hi guys, had my car for paint shop for 6 months aprox, is 2007 sl55 AMG , aircon dont work, we checked for gas it had gas, but added little. Cant hear the front radiator fan start when switch on aircon, cant hear compressor start either. fan and and tings inside seem like normal, no blinking lamp on the aircon switch .

Question is , are there any relays that that can be gone and where are they , or what can it be ? Find it strange compressor should be gone with less than 50 k miles.

car has installed Killer chiller system, but cant see that this should influence anything, is no leaks.

any good tip what it can be?

Compressor doesn’t have a clutch, so you won’t hear it. You will need some gauges to see how much refrigerant is in the system. These cars are by weight, and very sensitive to over fill or under fill. I usually evacuate and fill by weight. More work, but that’s really the only way to make sure it’s the right amount.

The sensor on top of the drier is forward and below the hydraulic pump fill cap. The sensor can be fowled by hydraulic fluid... clean the sensor.

I have cleared AC codes several times until the AC just starts working.

just the contact or some sensor, do i need take out gas first or ?

There are 2 wires going to the sensor on top of the drier. Oil can travel along wires into the sensor. The tape around wires traps oil. I remove about 10 inches of tape. Use electronic contact cleaner on wires and sensor. Wipe clean wires, blow dry sensor and wires with compressed air.

You may want to disconnect the negative battery cables before you soak sensors.

why, is it live electric there when ignition turned off?

If there are any errors in the Climate control unit (KLA), then the system will not work. I bought my car with front end damage, replaced the AC condenser and refilled the refrigerant. Nothing worked until the error was cleared (after the accident, the system detected low refrigerant level and shut itself down). Hope this helps.

What others said about the sensor and fill pressure. There is a low pressure sensor that if triggered will not let the coolant flow, helps protect the compressor. Most all cars are now filled by weight but you can still fill by pressure. Just need to use a R134A chart and adjust for ambient temperature.

was looking , is some wires down there, all connected with 2 nuts , is hard to see ,have hoses for killer chiller and drag race valve around this place also not so easy to work around. But the wires looked dry from what i could see. Is it some relay somewhere ? fuse witch one ? fuses in 2 boxes front is ok driver and passenger side .

I use an OBD2 with DTC code reader scanner (Autel Diaglink) to read and erase air conditioning (AC) codes. I have had to erase a code, try running AC, erase code several times to get AC to work.

What is the A/C code you are having to erase?

Get it on a good MB scanner like STAR SDS.

You will be able to monitor the high and low pressures, temperatures, Pump demand and Pump actual displacement.

The compressor works by PWM (Pulse width modulation) and is a variable displacement pump, and runs constantly, even when turned off.

If the system ever goes into fault, such as low gas pressure, it will "lock out" with a code, and you need to clear the code for it to start compressing again. You need it pumping to fill the system correctly.

OOPS.... 4 wires

Yep. O ce an error code is triggered, the system will not work until it's reset. Even if it's as simple as low refrigerant, the system will not become reoperational until it's reset. The ICarsoft MBII, and better scanners, are capable of resetting the system. Does not necessitate STAR level system access. But once the system is turned off by a fault it will NOT reingage on it's own without an actual reset. (Ie, every time the system shuts down due to low refrigerant, it must be reset to become operational again).