12.11 The pumps do not start
• The power supply is switched on.
• The selector switches are in position AUTO or ON.
The display is off
Cause Remedy
The control-current fuse is blown. Solution 1
The supply cable to the controller is defective. Solution 2
The connections of the controller supply cable are loose. Solution 3
The main board is defective. Solution 6
The cable between the main board and the display is not con-
nected properly or is defective.
Solution 7
The problem is still not solved. Solution 4
The display is on
Cause Remedy
The pump supply cable is not
connected properly to the con-
troller.
Solution 3
The pump supply cable is de-
fective.
Solution 2
The display indicates a liquid level which is lower than the level in the tank
Cause Remedy
There is a leakage in the level
sensor.
Solution 5
Solution 1
1. Find and eliminate the cause.
2. Replace the fuse.
Solution 2
Replace the cable.
Contact the nearest Grundfos sales company.
Solution 3
Tighten the cable connections.
Solution 4
The controller is defective.
Contact the nearest Grundfos sales company.
Solution 5
• Check the connection between the pressure tube and the pressure hose.
• Check the connection between the pressure hose and the pneumatic coupling underneath
the controller.
The hose is connected correctly when you cannot pull it out without pressing the locking
mechanism.
• Check the connection between the pressure hose and the pressure sensor on the main
board.
Solution 6
1. Check that all the connections to the main board are tight.
2. If not, the main board is defective and you must replace it.
Contact the nearest Grundfos sales company.
Solution 7
Multilift MD1, MDV | Fault finding the product| 43
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