Two senders shorted out together on genset?

[msponer]

Hi All,

Our exhaust gas temperature and coolant temperature senders shorted out at the same time.

I've ordered replacements, but wonder if this is common. Is it likely that the failure of one would burn up the second one? These are both in series in the automatic shutdown circuit, along with an oil pressure sender (which is fine).

I don't want to replace these and them have them burn up again if there is a root cause that could have shorted them both out at once. However, the circuit is pretty straightforward: Start Switch -> Oil Sender -> Exhaust Sender -> Coolant Sender -> Run Relay.

What do you guys think?

This is a Westerbeke 8BTD.

Thanks.

Matt

[jamhass]

Check for shorts (or opens) in the wiring itself.

[boatbod]

Senders or alarm switches? I'd be surprised if you have an exhaust gas sender... normally these are over-temp switches used to shut a genset down upon loss of raw water flow.

[Cheechako]

Hmmm.... being in series it's hard to fathom how one going out would even allow the other to. If one blows there is no flow of electricity to the other. Are you sure they are in series?

[Sailmonkey]

Originally Posted by Cheechako

Hmmm.... being in series it's hard to fathom how one going out would even allow the other to. If one blows there is no flow of electricity to the other. Are you sure they are in series?

Typical generator shutdown system.....NC for exhaust, NC for Jacket water temp, NO for oil pressure. All in series, the change in state of any of the three will deenergize the run solenoid and save the engine.

It's not unheard of to find more than one bad.

When you say "short" what do you mean?


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[Cheechako]

Originally Posted by Sailmonkey

Typical generator shutdown system.....NC for exhaust, NC for Jacket water temp, NO for oil pressure. All in series, the change in state of any of the three will deenergize the run solenoid and save the engine.

It's not unheard of to find more than one bad.

When you say "short" what do you mean?


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Could be short or open depending on the system. In "series" implys to me that if one fails the others have no connection.... as they become open to ground or closed to ground rather than acting independently. If you have two NC and one NO, they cant be in series right? As the NO would now be grounded thru the series connect to the others...?

[Sailmonkey]

Originally Posted by Cheechako

Could be short or open depending on the system. In "series" implys to me that if one fails the others have no connection.... as they become open to ground or closed to ground rather than acting independently. If you have two NC and one NO, they cant be in series right? As the NO would now be grounded thru the series connect to the others...?

The NO becomes closed when the oil pressure rises. That's why you need to hold the preheat switch down on older generators, to bypass the shutdowns until the oil pressure rises. The preheat switch supplies power to the run solenoid until the oil pressure switch closes.


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[TxCoastSailor]

I just replaced both the water temp and exhaust temp switches on my Westerbeke generator as well. Temp switch shorted out and I broke the exhaust switch while tracking down the problem. Brilliant!