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Old 07-05-2017, 11:06 PM   #1
dvd
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Instrument Voltage Regulator

I've got a fairly new (2010) Cummins with electronic engine read-out. Been running fine the past several weeks, about 5-7 hrs/day. Today the oil pressure reading started jumping around by 3-5 psi, the alternator voltage reading kept moving from 13.8 to 13.9 and back and the tachometer reading kept fluctuating by 10 rpm. The engine was running fine. If this were an older engine, I would think the instrument voltage regulator was going bad, but with the electronic read-out panel, I would be surprised if such a rudimentary thing would be included in the circuitry.

Any ideas?

Thanks,
dvd
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Old 07-06-2017, 05:36 AM   #2
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"Any ideas?"

The usual suspects , poor ground , bad connection , loose terminal end.
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Old 07-06-2017, 07:08 AM   #3
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System voltage could be changing by 0.00001 volts and that could make the display change from 13.8 to 13.9 as that is as much resolution the display has. Likewise with rpm, low resolution, changes in 10 rpm increments.

Oil pressure is different, it has 1psi resolution (I think), so might have a flaky sensor.

What happens if you select a cruising rpm say 100rpm higher or lower?

Got any DC loads running that have variable draw, like autopilot? That can cause volts to vary.
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Old 07-06-2017, 10:27 AM   #4
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Thanks for the ideas. Yes, I have been using the autopilot a lot, although the same over the past few weeks without these issues. I agree about "the usual issues" and will crawl down to the ER this AM for a wire/connection check and will probably access the back of the instrument panel tomorrow as I am planning on being in port (Prince Rupert) for a couple of days. Also, I found the 132-page manual for the "Vessel View" system which is installed on my boat. It's like reading a computer manual, but I did find out that there is a "Factory Reset Sensor Function" which queries all inputs to check for faults. That sounds like a possibility also.
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