The automatic feature of my aft bilge pump
was not working. PO had installed 3 float switches on a vertical plane - actually mounted to an old batten fastened so that to repair you just remove a bolt and lift
the whole thing up out of the bilge
Anyway, top switch is for an alarm
. Middle and lower switches have me confused. All are wired to a 12vdc relay inside an electrical
junction box. Looks like the relay itself is bad. I can manually close the contacts and the pump runs. Meter across the float switch leads tells me the switch is bad.
New switch installed and since the relay is bad I just wired it the old-fashioned way, between the power source and the pump. Works fine EXCEPT that it now short-cycles. The discharge hose run is quite long and the water
draining back into the bilge
when the pump stops is enough to activate the switch again.
I suspect that the old relay unit was an arrangement where the middle float switch (now unused) would start the pump, and the lower switch would shut it down when the water
got to the low limit. That way the hose contents draining back would not restart the pump. Since I don't think they make a choice of normally closed or normally open float switches, the relay had to be the key.
Solid state I know this calls for an SCR - once trigger voltage is applied via the mid-level float it would run until main voltage is removed by the lower float switch. Do they make one or do I have to build it?
I don't have a schematic and there's no stamping on the relay, which seems to have 4 primary and 2 secondary terminals.
Since I'm sure this is a common issue with bilge pump
drain-back, I'm hoping there's a wiring
scheme or specialized controller to handle this? Maybe a neat-trick way to wire a pair of float switches to accomplish this?