Coolant Circulation Pump
Back to: WIS 83.40 Automatic Climate Control (ACC) or Heating Ventilation and Air Conditioning (HVAC)
Description - Coolant Circulation Pump
The Coolant Circulation Pump (A31/m1) is also known as - "Auxiliary Water Pump".
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Issues - Coolant Circulation Pump
A common issue is a failed circulation pump which is part of the Duo Valve Assembly.
- It may be hard to notice that your coolant circulation pump (A31/m1) is not working properly.
- If the pump is dead, then in cold weather the car could not be heated more than 30C even if ACC was set to "HI".
- Another indication is the lack of heating when the residual heat option is activated with the engine off although heating is available with the engine running. To see how to activate the residual heat option go to the Section "Residual Heating/Cooling" under Heading "Function - Automatic Climate Control (ACC)" in
WIS 83.40 Automatic Climate Control (ACC) or Heating Ventilation and Air Conditioning (HVAC)
Several failure mechanisms are possible for a failed circulation pump including;
- Blown or damaged electrical circuit supplying power to the Circulation Pump.
- Seized Circulation Pump.
- Worn brushes in the Circulation Pump Motor.
The next figure shows an example of a Coolant Circulation Pump with very badly worn brushes.
A new pump is expensive (about US$200) but a DIY fix is possible if the failure is due to worn brushes. See below.
Parts - Coolant Circulation Pump
- 0 392 020 066" or 0392020066
- A2208350064
Diagnosis - Coolant Circulation Pump
- Error code: B1416 "The component or the signal line to the component A31m1 (coolant circulation pump) has short circuit to positive or overload."
- Note: error code B1416 is thrown if coolant circulation pump draws >5A current.
Testing - Coolant Circulation Pump
- I removed the pump and connected it to 12V DC. The pump did not spin at all (it was completely stuck and I could not rotate it even by hand) and the multimeter showed that it consumed 5.5A current.
Conclusion:
While you can buy a brand new pump for 140 EUR you might as well try to repair it. The reference shows how you can do it.
DIY Procedures - Coolant Circulation Pump
Repair - Coolant Circulation Pump
Acknowledgement of contribution by BenzWorld Member, Pokseva.