Understanding bilge pump wiring

PSNI

Member
Aug 2, 2017
60
Boat Info
2000 380
Engines
Mercruiser 8.1 MAG (2005)
My forward engine room bilge pump switch was lit up while in the off position indicating (I believe) that the float switch was engaged. I don't believe the pump was running and pulled out the rocker switch to test the wiring,

1. The rocker switch itself was somewhat warm. Is being lit for a period of time enough to heat up the switch or might this indicate something failing on the switch? The continuity of the switch leads was correct in the off and on position.

2. After reattaching the wires onto the switch it did not light up at all in either the off or on position. Now there is no voltage on the wires. The breaker on the panel has not tripped. The aft pump works fine. Could the wiring in the pump have somehow failed or become fried so that the circuit is broken? Is there a way to inspect/test this?

3. I studied the wiring diagram in the manual and there does not appear to be a fuse anywhere in the circuit. I made a line drawing to I could have a single view of the complete circuit. Does this look correct?
Capture.JPG
 
Very close but not quite,

Think this way the wire from the float to the pump is the same wire as 304, it's not a third wire to the pump.
The pump itself is only 12+ and ground
So when the float is "on" 300 connects to 304 and the System Monitor sees the pump is "running"
The same happens if you manually turn on the pump with the switch, the pump and the System Monitor get 12+

If the motor is "locked rotor" it may or may not blow the fuse...

Was there water in the bilge that would have had the float switch on?
 
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