Westerbeke 7.6: BTD Oil Pressure Switch

[R_C]

While isolating a recent problem to the fuel shutoff solenoid I noticed that my genset has two oil pressure switches mounted side by side. The schematic shows only one. When not running and still installed, one tests with continuity and the other no continuity. Can anyone explain the purpose of the two switches or point me in the direction of a schematic? I understand the oil pressure switch is bypassed during startup bythe preheat switch. But I don't understand why two are required. Could it be due to a remote start panel?

- Rick

[GordMay]

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[R_C]

Thanks Gord. In addition to the two oil pressure switches, the revised schematic also shows the fuel solenoid's current timer module, which was not included on the schematic that came with the genset.

- Rick

[CuttySark]

I've talked to Westerbeke technical support on this issue. It is my understanding that the auxiliary pressure switch PN 11552 is not used in most applications. It is sometimes used to send a signal to the helm on Sea Ray boats. It will have wires containing black attached to the terminals. It is normally closed. The other pressure switch PN 37323 is the one that controls the DC power to the K2 relay. It has wires with red and is normally open in its static state. It is bi-passed during startup by closing the pre-heat switch. As the oil pressure builds to 10 psi, the switch will close and stay closed unless the pressure drops below 10 psi at which time it will open, cut off power to the K2 relay and shut down the generator.

[R_C]

CuttySark,

Thanks for clarifying and confirming that one oil pressure switch is normally open and the other normally closed. It's important to know the switches are different when troubleshooting and to have the correct part numbers. The updated schematic I have also verifies the wire colors you list although it's often difficult to confirm with all that red paint. The schematic shows one side of the auxiliary oil pressure switch (#11552) connected to TB2-8, which isn't connected to anything else. When I am back on the boat I will try disconnecting the auxiliary switch while the genset is running, which should have no effect. Thanks.

- Rick

[CuttySark]

I'm not sure what 11552 would be used for. However, I assume that it works the opposite of 37323. It probably opens at 10 psi and closes at if the psi drops below 10. That would close a circuit and possibly send voltage to a low oil pressure light at the helm. The important thing to know during trouble shooting is that 37323 is the critical switch. On my boat it is the lower switch. On some others and in the diagram, it is the upper switch. You need to look at the wire colors to distinguish, since both switches look the same.

[R_C]

I'll also make a note to check my spare when I return to the boat and make sure it is 37323 and not 11552.