Electric coolant pump running & battery discharged

[estate130]

Hi - after some advice.

After unlocking my 2015 1.6 BMT Passat, one of the aux electric coolant pumps starts to run. This happens constantly and whether car is hot/cold or during DPF regeneration or not…

If the car is left unlocked - pump will run constantly.

If relocked - pump will run for around 15-20 mins then stop.

This cycle will flatten 12v battery over a day or so if car is not used but open/closed a few times.

Main dealer have investigated & changed a relay - but no improvement. If anyone can advise before I go back - then would be appreciated

Thanks

[Crasher]

PM me the reg or post the VIN.

[estate130]

Hi Crahser - just PM'd you details
Thanks

[Crasher]

You have two additional electric water pumps, the V188 at the front of the engine for the intercooler and the V488 at the rear of the engine which is the heater support pump. These are both controlled by the ECU but unhelpfully both use the same fuse 27 in the engine bay fuse board, separate fuses would help with diagnosis. You need to identify which one is running on and also whether it is Bosch 5G0 965 567 but now 2Q0 965 567 A or Pierburg 5Q0 965 561 B, thankfully the V188 and V488 are the same part numbers. I have seen a lot of these pumps fail and on your version failure of the V188 can give a cavitation fault code for the V488.

[estate130]

Thanks for this. Very useful. I will take a look based on your information

One additional question - I assume my assumption that the pump should not run on continuously in this way is correct? But the pump might run some of the time when the engine is not running - dependant on conditions?

[Crasher]

The ECU commands them but if the internal controller fails they can stop when they should be running or not stop when they should do depending on how they fail.