Engine Wiring Harness

[rpwillia]

Last big trip with a few hours to go I noticed my engine control panel no longer had power. This happened about 10 years ago and at that time one of the wires had broken inside the connector on the breaker on the back of the engine. This time it appears to not be so easy, and a couple of symptoms have me scratching my head and thinking I either have a short in the wiring harness or something else going on. Here are some of the symptoms. FWIW, I am leaning toward getting a new engine wiring harness at Catalina Direct has them for $129, and am planning on doing that if the consensus is the harness.
1. Getting no power at the 20 amp Circuit Breaker on the aft port side of the engine right below the lift pump.
2. Getting now power at the Preheat Solenoid (last time I jumpered from here to the breaker temporarily until I found the break).
3. With the key on, at one point when I jiggled the harness at the rear of the engine I could hear the low oil pressure alarm at the alarm panel.
4. But, when I jumpered from the lug on the starter to the circuit breaker to bypass part of the wiring harness it was tripping the breaker when I turned the key on.

So, I think it is the wiring harness, but am still a little confused by the symptoms.

I could also use some info on the PreHeat Solenoid as I took pictures of it before I disconnected the connections (I pulled the harness today and am planning on doing an ohm check in the morning) but the only marking on it is "12v" and it would be nice to have a better idea of what connections/colors go where (there are 2-3 different sizes and connectors so that helps). When I google it, I get the solenoid for my Kubota tractor which is not what this is.

Any other $0.02 you all can provide would be greatly appreciated.

 

[rpwillia]

FWIW, I found the wiring diagram for the Preheat Solenoid, makes more sense now.

 

[Stu Jackson]

Ray, usually the wires are OK, it's the damned connectors that corrode and fail. Also, my experience us the color coding is usually good unless some goon at the factory had a really bad day.

FWIW, I found the wiring diagram for the Preheat Solenoid, makes more sense now.

 

[rpwillia]

Thanks Stu, The color coding on the wiring appears to be spot on. It is driving me crazy that the symptoms are changing a bit and all of the connections seem to be good. The boat is now 24 years old and I am wondering if all that vibration over the years has causes a break inside one of the wires.

 

[Stu Jackson]

That would depend on what the wires were made of. If solid, perhaps. If stranded, unlikely. Best troubleshooting would be to ID where you think the fault may have occurred and work from there. Intermittent stuff is always a PITA, and lots of electrical is just that. Remember, "looks good" connections usually aren't, so cleaning and resetting is best.

wondering if all that vibration over the years has causes a break inside one of the wires.

 

[east coaster]

Agree with Ralph, go over all connections especially the engine ground. They should all be very shiny and gleaming also light coating of dielectric grease to keep them that way for a long time. On my 2002 310 the erratic electric problem on the westerbeke m25 xpc was combination of faulty corroded engine ground and oil pressure switch located on the port side of the engine and difficult to get at and work on. Using an acrylic mirror to see what I was doing and corrected the loose faulty electrical connection. Everything is fine now as all the connections have been clean and greased . Cannot reinforce enough that faulty corroded electrical connectors are responsible for many mysterious electrical issues onboard. Take the time to do this very rewarding task. My thoughts and experiences, thanks.

 

[rpwillia]

Stu, East, Thanks for bringing me back to earth. Turns out the wire broke inside the connector that joins the starter lug to the preheat solenoid wirea and the preheat solenoid to the engine breaker wire. The shrink wrap was holding them together, and the thing was on the bottom of preheat solenoid, so to get to it, I had to pull that whole mess out. All is good now.