Westerbeke oil pressure gauge shows maximum

[Magic]

Has anyone had their Westerbeke Gen oil pressure gauge go max while running?

I disconnected the sensor and measured the pressure sensor, which appears to be working (cold: 365 ohms, hot: 85 ohms). Gauge drops to zero when disconnected and jumps to max connected. Faulty gauge? The generator is running fine, oil is good, temp rises to normal.

Here's the sensor:

Thanks

Magic

 

[Scott215]

Did you clean both connections. At switch and gauge

 

[Magic]

Did you clean both connections. At switch and gauge

yes, the electrical connections.
I haven’t tried bypassing the wire to the gauge with a new wire, but tapping it on and off the sensor causes the gauge to go from zero to max.

 

[km1125]

I'm confused by the "cold: 365 ohms, hot: 85 ohms". Did you mean "not running:365 Ohms, running: 85 Ohms"?

 

[Magic]

I'm confused by the "cold: 365 ohms, hot: 85 ohms". Did you mean "not running:365 Ohms, running: 85 Ohms"?

yes, sorry. I was thinking the resistance would also likely be high when the engine first starts, before pressure has built. Referred to that state as “cold”.

presumably as resistance drops as pressure builds, voltage increases to the meter. I measured that at about 5.6v.

 

[km1125]

It's a pretty simple circuit... just from sensor to gauge, so either the sensor is dropping too low on resistance, or the meter is now "too sensitive". Not sure what the specs are for the sensor but I'm sure they're out there somewhere.

EDIT: Poking around a bit and thinking about this. The one test in my WB manual says to ground the wire at the sensor and the gauge should go to full scale - not pinned. Looks like you needle is past the full-scale mark, so I'm wondering if that indicated a gauge problem.

Also, just checking... do you have remote gauges? If you do, do they both read high, or is it possible there's a break in the line to the other gauge (which would flow more current to the only gauge left and have it read much higher than normal)?

 

[Magic]

Hmm, I wonder if the mechanic used the wrong viscosity engine oil with the last service. Maybe this would change the pressure response from the sender giving a lower resistance and higher voltage to the meter??

the manual says SAE 30 (10W-30)…need to check what they used.

No remote gauges for the generator.

 

[km1125]

Also wondering... does the light on the gauge work? It uses the same ground as the meter, if it's not working it could be due to a poor ground (which might be inside the meter) and cause the reading to show higher than actual.

Also, when you wrote "Gauge drops to zero when disconnected and jumps to max connected." Does it do this even when it's not running? You'd have to hold the "preheat" switch while the generator is not running to activate the gauges to do this test. If it jumps to max without the engine running then I'd definitely say there's a problem with the gauge.

 

[Magic]

Yes, the light works.

And yes, if activating the pre-heat switch on the engine control panel while the generator is not started, the gauge rises to max.

should this remain on 0kPa while pre-heating?

 

[Magic]

Ordering a new sender, although the mechanic advised they used 15W-40…hmmm.

 

[km1125]

15w-40 isn't going to make much of a difference at all over 10W-30. I would not be concerned about that at all.

If it went full-scale with just the pre-heat switch then I'd lean towards the gauge itself having an issue. IIRC, you measured the sensor at 365 ohms with no oil pressure and 85 with pressure, so those seem reasonable.

You might try pulling the lamp out of it and seeing if that makes a difference. If it's using the same ground and there's an issue with that ground it might impact the problem. It all depends on how it's all tied together inside the gauge.

 

[Magic]

To complete this thread. It was a faulty gauge.