VDO Cummins "B" Instrument Wiring?

[Michael Loy]

These panels [370HP Diamond CPL 2208], have a loose circuit board associated with each engine panel at each control station. An alarm buzzer is part of each board. The ‘workings’ of this board
tion. The ‘workings’ of this board are a mystery to me as I can’t find documentation. According to the first attachment the volt meter has purple [ignition] on one side and purple/black thru the low volt LED thence to a two wire connector. This diagram does NOT show the circuit board. My system has purple/black via a two wire Packard, but this wire goes to the water-in-fuel LED. My system has purple going to BOTH sides of the low-voltage LED and purple to BOTH sides of the voltmeter.
The second attachment allegedly shows the wiring of my exact engine, but there is no purple/black or indicated connectivity with the gage panel. This confusion keeps me from correcting my symptom which is the port voltmeter AND low-voltage LED routinely show 10 volts and alarm EVEN WHEN THE ASSOCIATED ALTERNATOR IS charging strongly with good amps and voltage [measured by separate means]. The port system shows a fluctuating charge by the voltage meter [10 volts occasionally rising to 12.8] all while the actual voltage is rock steady.
May I be pointed to the correct circuit diagrams so I can fix this?

Topic

[Tony Athens]

This may also add to the understanding of the factory system…………..The PCB boat IS NOT needed for all the instrument to work properly. In fact, on a properly working system, the PCB can be removed from the panel and all of the instrument will operate as they should.. The PCB BOARD is there for one reason only–To have an “vital sign alarm system” for the engine.. It basically reads the return signal from the OP & water temp senders, monitors voltages, and has a 4th unused WIF circuit, and thru the PCB electronics,it give you an alarm system with preset data points that trigger the alarm buzzer..

In so many words, you do not even need it or have it connected to test the instruments as stand alone gauges. Again, this is tru with FACTORY wiring that has not been modified.

Tony

[Michael Loy]

This also might have had something to do with it

Connector at the engine

[Rob Schepis]

Thanks for the follow-up. Good you caught it before “auto-shutdown” enabled!

[Michael Loy]

Rob is CORRECT! Terminals were loose.

Thank you.
Problem solved.

[Rob Schepis]

Did you check the ring terminal connections under the circuit breaker to make sure that they are clean and tight?

[Corey Schmidt]

You’re dropping voltage somewhere with a bad connection… probably in one of the harnesses… start at the battery and work your way up to the panel until you find where the voltage drop is occurring… pull ALL of the harness connections apart and spray/clean them with WD-40 and a toothbrush…

Beede is the current Cummins gauge manufacturer… FYI

[Michael Loy]

Thanks to Rob & Corey

Rob, you were correct the red button 10amp ckt breaker had popped. Unfortunately, still low voltage in port engine harness although rapid voltage variations have ceased.

Corey, thank you for the Beede drawing [by the way, what does Beede stand for?]. I surmise the ckt board provides a ground source for the associated alarm LED at a level set in it’s circuitry. I can find no documentation on the board itself. I am at the point where your suggestion to start harness voltage tracking. For now, the red wire supply to the lower ‘ignition’ key is at 11.0 volts where the ‘source’ [START battery at the starter post] is at 13.4v under charge. Have to delay the laborious traut when I get at it I will report.cking for a few weeks,

[Corey Schmidt]

Correct Diagram…

Check this PDF for a reference that includes the alarm board… you need to get a voltmeter out and trace the path from the engine where you can CONFIRM good stable voltage… all the way up to the panel and volt meter gauges… maybe the gauge itself is bad? Have you tried swapping gauges? Have you tried connecting the gauge by itself to battery power to confirm its working as expected?

https://www.sbmar.com/wp-content/uploads/2016/03/Cummins-BEEDE-Engine-Panel-Wiring-Diagram.pdf

[Rob Schepis]

Engine Mounted Circuit Breaker

Check the red push button 10amp CB. Next to the aftercooler at the rear lifting ring.

I would post a pic or link but I’m on a dumb phone at the moment. You can search for it as we have had a few posts here already, pics included.

[Author]

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