Neutral nightmare

[TerryA]

I recently had to replace my fuseboard when the 40 year old original started to deteriorate. Positives were easy enough to swop over but the old board refused to budge despite me removing all the obvious screws. It turned out that it was secured by a number of neutral cables fixed to the back which became disconnected when I levered it off. I did some reconnecting and with the exception of the radio and the engine heater plugs things worked.
Can someone explain in simple terms please:
Why the radio just makes a blipping noise and doesn't turn on?
Why if the first, second and fourth positions on the ignition switch work but not the third?
Why I can't just connect all the neutrals together, if I do nothing works?

Help for the bemused gratefully accepted.

 

[Graham376]

Are you talking about VHF radio or FM car radio? Car radios have two positives, one being permanently connected for memory. If ignition switch position 3 is "heat" and your glow plugs activate via a relay, sounds like the relay negative may be missing. Both should be easy enough to check with a multimeter.

 

[TerryA]

That's s VHF radio. I'll certainly try the multimeter next time I'm on the boat. Unfortunately it has 40 years of wiring history, things removed and wires cut but not removed and things added but never identified or labelled.

 

[pandos]

That's s VHF radio. I'll certainly try the multimeter next time I'm on the boat. Unfortunately it has 40 years of wiring history, things removed and wires cut but not removed and things added but never identified or labelled.

I have been simplifying and rewiring also. Little issue with the positive cables but I have found many negative s which had rotted internally, and we're in places bridged or fed from random places...

Still cannot get my head around some of the negatives and what is connected to what and where they meet.

 

[TerryA]

Just to add to the confusion I have wiring for the bow thruster battery in the bow, two battery chargers, a starter battery and a mystery with the two domestic batteries. Theses are linked positive to negative which I think would give a 24v output but I can't find anything that is 24volt. Of course they both have other leads attached as individual 12v batteries. All confusing.