Weird water pump switch behavior

The pump light has been coming on spontaneously since I dumped last time.

Any ideas on what to try or where to look?

Other than the light, it he pump working correctly?   You might want to pull the fuse and then
reinstall it, see if that corrects the problem.  It also might be a bad switch.  In which case, unscrew
(or unsnap) the switch cover and check the wiring.

Are you 100 % sure you're not losing water somewhere, causing the pump to kick in ?

There are three switches for the water pump; kitchen, bath, dump station.  All three turn spontaneously on at the same time.  When a switch light is turned on the pump will activate only when the line pressure drops. 
However, because the coach is connected to external water pressure, the pump does not run when a faucet is turned on. Evidently the pump  is not part of the issue.
The switch connections in the sewer area have been checked and reseated... hopefully to assure good contact but no improvement seen.

There are three switches for the water pump; kitchen, bath, dump station.  All three turn spontaneously on at the same time.  When a switch light is turned on the pump will activate only when the line pressure drops.
However, because the coach is connected to external water pressure, the pump does not run when a faucet is turned on. Evidently the pump  is not part of the issue.

First on the hit parade should be checking for a leak.Which I'm sure has already been done.  Verify that the toilet valve is not the problem.   If there are no suspected leaks, check the wiring to the pump.  Particularly the ground connection.  Low voltage can cause the pump to remand [on].  While you're checking out the pump, make sure that the mounting bolts are tight.  Keep investigating, and you'll find the problem.

Aha!  Found it.

My amateur radio transmissions are feeding back somehow to turn on the switch control system.

There is a latching relay that provides power when any of the three switches are pressed.  This relay is underneath the passenger side bed on our 2552.   The relay is on the bottom in the photo.   This is a long shot but thought I would mention that as it could exhibit intermittent symptoms causing the pump light to come on or off.

Aha!  Found it.

My amateur radio transmissions are feeding back somehow to turn on the switch control system.

Ahhh...RF Voodoo!

My son is a ham operator and when he was just learning (on a really old piece of equipment), he kept opening the garage door.  Glad you found the issue!

Fandj,

 Excellent suggestion.  I will try to locate it and see if ferrite snap-on chokes will help.

The relay is under the frig.  Ferrite chokes on each of the five wires made no improvement.  Oh well...

grounded tin foil shield?