Question: I have a Magna 3 that has a red light and and a dry running error code number 57 causing it to stop running. After cleaning out the sensor (was dirty) and still having the same issue, I replaced it with a new one and still the same code. Any suggestions?
Answer: Normally the dry running error code is caused by particulates blocking the senor eye and tricking the pump to think that there is not enough water passing through. In your situation, when you replaced the sensor most likely you did not replace the sensor wire. Make sure to sue the new one supplied, it is upgraded from the old one. In some rare situations, the sensor wire connection will have a build up (see picture below) and give a false reading.
The new sensors (Grundfos P/N 98471249) come with a newly designed wire connection that now protects the connections much better.
On another note, when removing the sensor, be sure to see that the rubber boot ( shown below) comes out of the well. Often it will stay stuck inside when pulling out the sensor. It should also be cleaned along with the sensor eye when servicing it.
For additional information, contact your local wholesaler or Grundfos rep agency.