Low Voltage at ignition switch?

[JSMoore]

1987 Mark Twain, MTC 215
4.3 OMC Cobra
Dual Batteries with Perko Switch

I was curious why my hour meter wasn't working. And, while digging into that problem, I found it was only getting 10.8V from the ignition switch. (wired + to ignition on & - to ground) When switch is on, volt meter in dash shows, 10.8V. Everything I checked under the instrument panel is getting 10.8V. Both batteries check 12.9V at the terminals. When you start the motor, volt meter in dash jumps up to 13.7v, along with everything else.

Everything works fine, (except the hour meter). The motor cranks fine. There doesn't seem to be any issues except the loss of voltage between battery and ignition.

Any ideas why I wouldn't be getting full battery voltage at the ignition switch until I start the motor?
Thanks!

 

[bigfoot07]

Re: Low Voltage at ignition switch?

it sounds like you have a corroded connection or a loose connection between the battery and ignition switch.for some reason you have to much resistance in that wire.with the engine running your alternator is putting out about 14.0 volts and thats enough voltage to over come the wiring problem.try to follow the wire from the battery all the way to the ignition switch and see if some thing is corroded or loose

 

[JSMoore]

Re: Low Voltage at ignition switch?

Corrosion was my thought, too. Unfortunately, it's going to be hard to follow/check the wire all the way through. It's part of a bundled wiring harness. So, I may have to bypass some wiring around the harness to correct the problem.

Thanks for the input, bigfoot07!
JSM

 

[Silvertip]

Re: Low Voltage at ignition switch?

Your post indicates you have a dual battery switch. If the problem exists on only one battery or the other, the problem is between that battery and the switch. If it is the same on both batteries then the problem is between the switch and the ignition switch. My suggestion would be to disconnect and reconnct (several times) the main engine harness plug. Just burnishing the contacts may resolve the issue.

 

[JSMoore]

Re: Low Voltage at ignition switch?

Thanks, Silvertip. The problem DOES exist in all switch positions. Just gotta get time to dig in there and do that kind of needed maintenance. For sure, I will be cleaning contacts and connections before I go trying to figure out how to string new wires.
Thanks!
JSM