Re: Help with wiring a 25hr electric start
The switch is just a make-or-break type connection for the ignition, so you need to find the two posts (contacts) that are the common points for the ignition hot lead. You should be able to eliminate one post (there will be several posts/contacts, as you will have the pass-thru hot lead when the switch is on (that will be the two posts I mentioned), a ground, which should be a black or green wire...and some other posts which are for accessories, and will be jumpered off the "in" hot lead on the switch. Most likely, those will be connected with red, or red/white, or orange or orange white wires, and will lead over to your gauge cluster, or other accessories...
You will need a volt/ohm meter, with a continuity test function.
Make sure the key in in the OFF position.
Set your meter to the 12 volt DC setting. Look for the biggest diameter red wire going to the switch...that should be your "IN" hot lead from the battery. Touch that post (or if you cannot reach it, push the point of the red colored probe from your battery tester into the wire, being sure to penetrate the wire jacket and make contact with the wire inside). Touch the other (black) probe from your meter to a good ground. You should see a reading of around 11.5-12.5 volts. If you do, you know you have found the hot lead TO the switch. If not, try another wire, until you find the hot lead.
Now, disconnect the boat battery.
Check the same wire again..it should now show NO voltage.
Set your meter to the "continuity" setting, and touch the two probes together. You should hear a beeping noise. That indicates that you have continuity (a complete circuit, so to speak.)
Now back to the switch...put one probe on the wire you identified as the hot IN wire. Turn the key on...touch the other posts, one at a time, with the other probe. When you hear a " beep" from the meter, you should have found the post that has the hot "OUT" wire (the one that feeds the ignition circuit at the motor). Check all the posts, to make sure you have found the right one.
Now that you have found those two, you know which are your main ignition leads. You should also know which is your ground lead. So everything else is a feed to an accessory, or a guage, or the light circuits.
Turn key off.
Hook battery back up.
Turn key back on.
Turn all accessory and light switches on. Remove the other wires from the contacts, one at a time, and see what goes off. In some cases, the same wire feeds more than on accessory, so make sure you note everything that goes off.....In my case, one of my bilge pumps was (improperly) tied into the wire that feed the dash lights). You may also find that several wires are jumpered off the same post...that is OK, as long as the total amp draw of ALL things tired to the post do not exceed the wires load capability, and or the fuse of circuit breakers max rating. Label the wire so you can keep track of what goes where. You should also write down on a piece of paper, the position of each wire on the switch, the color of each of those wires (ie: red with black trace: blue with yellow trace: etc) and what it goes to, and keep that some place safe, as a reference guide. DO NOT trust your memory on this. Write it down. Repeat for each post, other than the main HOT in and out leads, and the ground. You have now isolated what each wire goes to.
There are other ways to trace the wires down, but I have found this to be the safest, easiest, and surest way to do it. Just take it slow, and record what you find.
If the underside of your dash looks like mine did, it is a rats nest of wires under there, so trying to trace each wire back visually is almost impossible.
After you have isolated where each wire goes, and have labeled the wires, you can go ahead and clean up the whole mess under there.
Good luck.