Low Voltage Gremlin

[Justin Murphy]

I have single 6bta with the analog panel. I have run into an erratic low voltage and trying to trace it down. When the problem arises, I show about 8-10 volts on my cummins gauge panel and the starter will click or barely turn.

What I’ve done so far: New batteries, new starter cable to batteries, new magnetic switch and cleaned, re-sealed heat shrink connectors on wires, good grounds (new from starter to trans, the trans to battery is original but appears okay).

The trouble in diagnosing is that it sometimes fixes itself and I have yet to be able to get a multi meter on the magnetic switch to test solenoid.

I also have a stand alone digital voltmeter tied to my battery bank and I can see about 14v when the problem arises and the cummins gauge is reading 8 or so, so it certainly isn’t batteries. Where does the cummins gauge get it’s reading? Is it from the hot wire on magnetic switch? I am thinking of adding another ground to the common bus bar I have behind my dash going directly to the gauge panel (I’m not sure there is or isn’t one now), I think the entire panel is plugged into wire harness?

Thanks

Topic

[Justin Murphy]

Ground the panel to your battery separately from the engine harness. I replaced my engine fuse as well it’s a cheap fix and they can go bad as they get older.

[Jeffrey Fontes]

Its safe to say I am having the same exact issue.
I have good voltage everywhere, the batteries, the starter lug, the circuit breaker (both sides)
When i turn the key on my on dash volt meter is reading less then 10 and it will not crank.
The batteries have been load tested and passed.
i chased all the wires and checked connections and cannot locate the problem.
If i charge the boat it starts….. up. I cannot find or understand why i have a voltage drop when i turn the key switch on.
the air heater circuit was put on a switch… I didnt do this it came that way someone must have been reading this
if i measure at the key switch i lose over a volt when i turn the key on…….
I just cannot find what is robbing the voltage.
-Jeff

[Justin Murphy]

An update on my situation, I had two issues going on, about three feet of battery cable that wasn’t replaced with all other cable was corroded enough to cause intermittent starting issue along with a bad ground on the harness at the panel. Replaced those two things and all is well. Thanks all.

[Justin Murphy]

Thanks, I went today and it does appear I have 10ga, I’ll try your suggestion as well as cleaning all terminals again and replacing any suspect wires that I see. So it’s more than likely not a ground issue? Corrosion in wire causing voltage drop?

[Tony Athens]

Justin,

If I had an issues as you describe, I’d being using a standard 10A Blade fuse for testing purposes.. If you blow that, then your issue is in the wiring going up to the dash.. When your system is right, it should draw about 5-6 amps max, even during cranking.. We use a 5 amp test breaker for testing.

Tony

[Justin Murphy]

Also to point 2 in your response, I just replaced the circuit breaker, it got hot and wouldn’t reset, it’s definitely not 10ga so more than likely that’s what’s going on. Thanks again.

[Justin Murphy]

I’ll check wire size, I don’t remember it being 10ga, sounds like that could be it. I looked at the diagram yesterday and noticed it called for that size as well. I have already put my heater on a switch, thanks. Thanks very much, think I’ll just run some new wire and zip tie along harness up to helm and eliminate that.

[Tony Athens]

Cummins factory wiring diagram attached,

1) if you have a grid heater, put the circuit on a switch, or just disconnect it

2) From your description, I’d say it’s the harness from the engine feeding the dash that is your issue. The later harnesses had #10 wire for the ground (blk), the POS feed (RED) to the panel and the “purple” return feed to the engine.. The RED feed thru a semi-problematic circuit breaker on the engine………The early harnesses ones had 14Ga

Tony

[Rob Schepis]

Search the forum here for “engine mounted circuit breaker” with me as author.

[Author]

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