very strange 12V issue??

[capeshore]

Hello All, see what you think of this... Randomly my dash switches will be reversed and some not working? my hour meter starts clicking and the boat is off (battery switch on of course) Bilge switch light is on and running when in the off position?
Tried turning off Shore power,trace wires, etc.
Seems like some kind of grounding issue? Flushing the vacuflush might "spark" the issue or even just turning a overhead light on. Any thoughts as to how to approach this? Boat is a 1996. I Installed new ground buss and fuse buss, all connections are good there.

 

[Silvertip]

Re: very strange 12V issue??

I guess one needs to ask if this situation popped up immediately after adding the new panel and ground buss? If so, that's the place to start checking. I agree that it is a grounding issue although a back feed from another live circuit could be the culprit. When the issue arises, pull one fuse at a time and see if the problem goes away. If it does, that circuit is the problem. If pulling fuses doesn't make any difference in behavior, then the problem very likely lies in the "hot" side of the circuits feeding the fuse panel.

 

[capeshore]

Re: very strange 12V issue??

I guess one needs to ask if this situation popped up immediately after adding the new panel and ground buss? If so, that's the place to start checking. I agree that it is a grounding issue although a back feed from another live circuit could be the culprit. When the issue arises, pull one fuse at a time and see if the problem goes away. If it does, that circuit is the problem. If pulling fuses doesn't make any difference in behavior, then the problem very likely lies in the "hot" side of the circuits feeding the fuse panel.

Thanks Silvertip. Issue did not pop up immediately after new panels etc. I think I have tried pulling the fuses as you said.
I will do so today systematically though.
If it is the latter and a "hot issue" how can I troubleshoot that? Thanks for your help.

 

[Silvertip]

Re: very strange 12V issue??

Start with a very thorough inspection of your crimp connections on the HOT side of each switch. You are looking for stray strands of wire that may be sticking out of the terminal and touching adjacent terminals. Again, in a systematic approach, one at a time, disconnect one terminal on the HOT side of each switch. If the problem goes away when you pull a specific terminal, you have found either a bad switch or a bad connection. If you pull all terminals and the problem still exists, do the same for the LOAD side of the switch. Do not overlook a problem with the +12 volt and ground feeds running from the battery to the helm. If you have an automatic bilge pump switch you might investigate that (eliminate it temporarily) since one of its three lines may be wired directly to the battery. It may also have a manual/auto switch on the helm so that wire may go to the switch. You want to systematically isolate one circuit at a time to find this issue. Since the instruments on your boat are powered through the engine harness and ignition switch you want to check that as well. The instrument panel lights get power via the NAV/ANC switch which is powered via the boat harness (the black and red wires that run from the battery to the fuse panel). There are obviously lots of places for this gremlin to hide so to avoid frustration, do not just "shotgun" the issue by jumping from one possible thing to the other. Think logically.

 

[glenn property of pam]

Re: very strange 12V issue??

I agree with silvertips about thinking logically but my first thoughts on the problem described would be a back feed due to a bad ground.
electricity is not magic it follow rules and the main rule is it wants to get from positive to negative (cough) so power goes to a switch then goes to the item and back to negative. If it can not find a negative it will try to find another path and this is where the magic seems to happen. If you ever turn on one item and another one comes on especially bilge/anchor light/fuel gauge then run a temp wire from the battery negative to the first item negative buss and see if the problem goes away.

 

[NYBo]

Re: very strange 12V issue??

Randomly my dash switches will be reversed...?

 

[capeshore]

Re: very strange 12V issue??

Excellent guys, thank you..been chasing this ghost a little bit this summer..was a particular busy one and never sat down long enough to do as you guys say..must be done. Tons of places where it can hide.But being out of the water it is a perfect fall time problem to deal with...if any.

NYBo...... I agree very strange to have things working backwards as well. Thats the part that has me concerned the most. Has anyone ever heard of that before?

If I come up with anything that seems helpful in a general way I'll repost my findings and possibly check back in with a question.

 

[Silvertip]

Re: very strange 12V issue??

Visit the trailer section of these forums and you will see all sorts of odd light behavior and itis almost always due to a bad ground.