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Stan
Stan, Mercedes Technician
Category: Mercedes
Satisfied Customers: 3526
Experience:  Technical support engineer
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My 2012 c250 benz blows hot air even after changing

Customer Question

Hello my 2012 c250 benz blows hot air even after changing compressor,expansion valve and dryer .it blows cold air once in a while then hot air 95%
Submitted: 1 year ago.
Category: Mercedes
Expert:  Stan replied 1 year ago.

Hello,
Sometimes the probem can be caused by : Defective refrigerant line (engine-side low-pressure line, from compressor to connecting point upstream of expansion valve) whose inner coating comes loose in the flexible section of the hose, causing constriction.

To confirm this follow this procedure:

- No or insufficient cooling output, permanently or occasionally/ defective refrigerant line -

Topic number

GI83.00-P-047246

Version

2

Design group

83.00 General

Date

07-15-2009

Validity

Passenger car model series with air conditioning

Reason for change

Simplification of test steps
Complaint

No or insufficient cooling output, permanently or occasionally/ defective refrigerant line.

Cause

Defective refrigerant line (engine-side low-pressure line, from compressor to connecting point upstream of expansion valve) whose inner coating comes loose in the flexible section of the hose, causing constriction.

File

Designation

Ansicht Innen.jpg Inside view of damaged part

Remedy

Air conditioning system may not be evacuated before test steps 1. - 3., this could affect the test result.

1. Start engine, activate air conditioning on control panel (max. cold, blower setting 3), medium engine speed.

2. Connect pressure gauge to high and low-pressure side.

3. Check whether the refrigerant compressor is delivering refrigerant (limiter on belt pulley turns or pressure builds up in refrigeration circuit): If the refrigerant compressor is not delivering refrigerant, eliminate this fault. If the refrigerant compressor builds up pressure,

4. Read off the high and low-pressure values from the pressure gauges after approx. 5 minutes.

If the installation space does not permit reliable temperature measurement using an infrared thermometer, continue with 6:

5. If the low pressure is noticeably high (> approx. 4 bar) and the evaporator temperature is significantly too high at the same time (> approx. 10 °C) use an infrared thermometer to check the engine-side low-pressure line against the refrigerant flow direction (from compressor to connecting point upstream of expansion valve). If there is a noticeable temperature drop in the line (Delta > 8 °C),

6. Disassemble the engine-side low-pressure line (from compressor to connecting point upstream of expansion valve) and

7. 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).

8. Replace the line if you detect any constriction

Best Regards,
Stan