This bulletin refers to insufficient or no cooling output on Mercedes Benz vehicles, where a permanently or occasionally defective refrigerant line is present.
Constriction may result from an engine-side low-pressure refrigerant line from the compressor point upstream of the expansion valve, where the line’s inner coating comes loose in the flexible section of the hose.
- Start the engine. Activate the air conditioning on the control panel (max cold, blower setting 3), medium engine speed.
- Connect a pressure gauge to the high and low-pressure sides.
- Check whether the refrigerant compressor is delivering refrigerant (limiter on belt pulley turns or pressure builds up in refrigerant circuit). If the refrigerant compressor is not delivering refrigerant, eliminate this fault.
- Read the high and low-pressure values from the pressure gauges after approximately five minutes. If the installation space does not permit reliable temperature measurement using an infrared thermometer, continue with Step 6.
- If the low pressure is noticeably high (more than approximately 60 psi) and the evaporator temperature is significantly too high at the same time (more than approximately 50 degrees Fahrenheit), use an infrared thermometer to check the engine-side low-pressure line against the refrigerant flow direction (from compressor to connecting point upstream of the expansion valve). Check to see if there is a noticeable temperature drop in the line (Delta greater than 45 degrees F).
- Disassemble the engine-side low-pressure line (from compressor to the connecting point upstream of the expansion valve).
- Use an endoscope to check the line for clear passage (checking for clear passage using welding wire or similar is not permissible as this can damage the inner hose and cannot detect peeling anyway). A high-tech UV and endoscope lamp can be ordered directly from the manufacturer at www.waeco.com; P/N TP-9354.
- Replace the line if you detect any constriction. Refer to EPCNet for applicable part number.