Electrical problems

[Wazzergy]

Hi
I have electrical problems with my cummins engine. It started as soon as I bought the boat. When the engine is at tick over revs the voltage is dropping from 24v to about 18v holds there for a couple of seconds then goes back to 24 v for a few seconds then drops off again. It's not a meter problem as the boat lights dim at the same time. About 3 weeks ago the digital hour meter stopped working its just a blank indication now. And yesterday when I went to turn off the engine it wouldn't turn off.
Today I took the alternator off and took it to a local electrical place to have it checked out and they say its fine, no problems.
I am now at a blank, not sure if the problems are all linked or I have 3 separate problems.
Any pointers would be much appreciated.

 

[Wazzergy]

I have now found out that the voltage swing is from the starting heaters cutting in and out. Apparently my cummins engine has an air heater to per heat the air to the engine and these are cutting in and out even when the engines hot.
Now to find out what's causing that!!

 

[cimo]

don't know your engine. if its a manual preheat, then your keyswitch/preheat button (and relay?) as a starting point.

 

[Rossynant]

And if automatic - are the idling revs as should be, or too low? Set the speed as should be, or bit higher, and see.
But then also alternator may stop the charge with revs too low for it. Don't know the engine, but it would be no surprise.

 

[savageseadog]

I would check the wiring and cable terminations