Manual glow plug switch

[JerryK]

Jerry, I understand your modification and it is just the opposite of the OP's. It's easy to disable something and enable it when you need it. His problem is something doesn't work and he wanted to put in a switch to bypass the whole circuit because he would rather do that than buy a timer. That's a whole level of complexity above what you've done and quite the opposite of yours. He's far better off replacing the timer. In my opinion, I'd spend lots of money on timers before making a switch modification. As Soundguy pointed out, a switch that runs a high current relay is the standard way to do this. A switch that handles this much current and wiring to handle it is easier to say than it is to do.

Yup..!!! I don't know about the glow plugs, but them grid heaters sure zap the ^%$# out of the battery. Then you throw the starter load on top of that...and you can see the alt struggle to charge up all that you used. That why a lot of us Cummins owners unhook the grids when not needed, which is most of the year. Those big batteries are REAL pricey...