Mercedes-Benz E-Class W213 AC Blowing Hot Air

Symptoms

1. AC System Engaged: The air conditioning system is switched on, but only hot air is coming from the vents.
2. Temperature Fluctuation: The air temperature does not change regardless of the temperature setting.
3. Unusual Noises: The AC compressor may be making unusual noises when engaged.
4. Dashboard Warning Lights: Possible illumination of the AC warning light or check engine light.

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Diagnostic Steps

1. Visual Inspection

• Check for Obstructions: Inspect the AC condenser and radiator for debris or blockages.
• Inspect AC Compressor: Look for signs of damage, leaks, or corrosion.
• Examine Belts and Hoses: Check for wear, cracks, or disconnections in the AC system.

2. Check Refrigerant Levels

• Tools Required: AC manifold gauge set.
• Procedure:
  • Attach the low and high-pressure gauges to the corresponding service ports.
  • Record the pressure readings: Low side should be between 30-40 PSI and high side between 200-250 PSI (varies with ambient temperature).
  • If readings are low, the system may be undercharged.

3. Inspect AC Clutch Operation

• Tools Required: Multimeter.
• Procedure:
  • With the engine running and AC on, check if the AC compressor clutch engages.
  • Use a multimeter to check for 12V at the compressor connector. If there’s no voltage, check the AC relay and fuses.

4. Check for Fault Codes

• Tools Required: OBD-II scanner.
• Procedure:
  • Scan the vehicle for any fault codes related to the HVAC system.
  • Note any relevant codes and refer to a repair manual for troubleshooting based on those codes.

5. Inspect Blend Door Actuator

• Tools Required: Screwdrivers, possibly Torx bits.
• Procedure:
  • Remove the dashboard trim if necessary to access the HVAC unit.
  • Check if the blend door actuator is functioning properly; it should move when changing temperature settings.
  • Manually move the blend door to see if it changes the air temperature.

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Repair Instructions

If the Issue is Low Refrigerant

1. Recharge the AC System:
   • Tools Required: AC refrigerant can, manifold gauge set, safety glasses, gloves.
   • Procedure:
     • Evacuate the system using a vacuum pump if necessary.
     • Attach the refrigerant canister to the low-pressure port.
     • Open the valve and allow refrigerant to flow until proper levels are reached.

If the AC Compressor is Not Engaging

1. Replace AC Relay or Fuse:
   • Tools Required: Fuse puller, replacement relay.
   • Procedure:
     • Locate the fuse box; refer to the owner’s manual for the specific location of the AC fuse/relay.
     • Replace any blown fuses and faulty relays.

If the Blend Door Actuator is Malfunctioning

1. Replace Blend Door Actuator:
   • Tools Required: Screwdrivers, new blend door actuator.
   • Procedure:
     • Remove the actuator from the HVAC unit by unscrewing it.
     • Install the new actuator in the same orientation and reassemble any removed components.

If there are Refrigerant Leaks

1. Locate and Repair Leaks:
   • Tools Required: UV leak detection kit, sealant (if applicable), new o-rings, refrigerant.
   • Procedure:
     • Use UV dye and a black light to find leaks in the system.
     • Repair or replace the leaking component (hoses, o-rings, compressor).
     • Recharge the system after repairs.

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Conclusion

After following these diagnostic steps and performing the necessary repairs, your Mercedes-Benz E-Class W213 should return to proper AC functionality. Always ensure to use the correct specifications for refrigerant and components as per the manufacturer’s guidelines. If issues persist, consider seeking professional assistance from a certified technician.