Electrical problem-need advice

I opened my boat for the season today and found an electrical problem.
I turned on the AM/FM stereo, VHF, GPS and auto pilot (on once i turn boat on the auto pilot goes on). Everything runs fine......here is the problem;
1- once I squeeze the VHF mic, all the electronics turn off and on.
2 - if i ENGAGE the auto-pilot, all the electronics flash off and on.
Can anyone give me advice on where to start trouble shooting?
Thanks - Joe

 

You have at least one corroded junction. The equipment you listen doesn't draw much current so they are supplied from a common terminal block or connector.
Pressing the transmit button causes the current to the VHF to increase 10-fold; due to a corroded contact the voltage collapses at that moment.

It may very well be that the bad spot is not in the +12V circuit but in the return (ground). There probably is a common ground terminal located near the equipment. How that is physically done depends on the preferences of the electrician who installed it: it can be a row of screw terminals or contact lugs. Some use a single long screw on which all the cable eyes are stacked.

Once you have access to the wiring you probably can see the problem without measuring any voltages or currents because the contact place shows green corrosion products.

 

Hi sportfisher,

Reckon CDK has just about solved the problem as so many pieces of gear are attached, what he says makes real good sense

 

Thanks guys, i will be taking a look this week and will start with the ground connections. Could a connection be loose and not corroded? because when i was under the console last season the bus terminals looked like new, i guess i will see.
Thanks again, i will let you know
-Joe

 

Yes, ther often become loose, especially boats that have to be shipped from thhe original maker, we regularly have to go over the whole boats electrical connections and tighten em up. Have fun, and be very methodical, do not assume that anything is tight.