Engine Rewire Question?

[Dougal]

I'm having to rewire ALL the 12v wiring to and around the engine (Perkins 4.108). How would you guys go about all the earth returns? The original harness had all earth returns piggy backed on a single wire. I know this is common practice, on cars too, but if that one wire fails, all engine gauges fail with it. Any reason I shouldn't run individual returns?

 

[matthewriches]

Assuming you’re talking about the engine. Many earth to the engine block then off to the negative terminal or bus. Or to a single point then again, off to the battery negative.

In the case of domestics then your distro system should have a decent negative bus or several remote busses that link to a central bus.

 

[matthewriches]

Piggy back is not ideal for the reason you mentioned.

The small commercial boats with resistive senders have their own feeds to isolate complete failure.

 

[Dougal]

Yes, as I said, its the engine wiring, not domestics.
Having studied a little further, I think I'll do it as per the domestic circuits though... with each item individually earthed with its own wire, all terminating at a bus board connected with heavy gauge to battery earth. Thankfully, nothing appears to be earthed to the engine and no heavy battery to engine cable.

 

[matthewriches]

That’ll be a clean job.

I presume your alternator and starter both have their own connections also?

Yes, as I said, its the engine wiring, not domestics.
Having studied a little further, I think I'll do it as per the domestic circuits though... with each item individually earthed with its own wire, all terminating at a bus board connected with heavy gauge to battery earth. Thankfully, nothing appears to be earthed to the engine and no heavy battery to engine cable.

 

[Hadenough]

Yes, as I said, its the engine wiring, not domestics.
Having studied a little further, I think I'll do it as per the domestic circuits though... with each item individually earthed with its own wire, all terminating at a bus board connected with heavy gauge to battery earth. Thankfully, nothing appears to be earthed to the engine and no heavy battery to engine cable.

That's the way I did it with a ring terminal bus bar with an 8mm end post back to earth. (Beam me up Scottie - must be the way you are feeling Makes for easy connection/disconnection/fault finding. I did the same with the L and was anal enough to match terminals L - N circuit for circuit on the bus bars.

 

[<152587>]

Yes, as I said, its the engine wiring, not domestics.
Having studied a little further, I think I'll do it as per the domestic circuits though... with each item individually earthed with its own wire, all terminating at a bus board connected with heavy gauge to battery earth. Thankfully, nothing appears to be earthed to the engine and no heavy battery to engine cable.

So how does the start motor cope with negative, presumably it connects to its own terminal on the motor?

 

[Dougal]

Yes, has both positive and neg supply cables