MSefi.com read only forum (Jan.15,2018)

Is the switched power which connects to the relay board a high draw circuit, or is it only a signal to pull in a relay, using the unswitched power on the board for the high current draws?

I’m asking because my car was initially carbed and I’m sure the (Lucas) ignition switch won’t handle much current draw. Do I need supply a high amp switched circuit to power the board, or can I use a low amp circuit from the ignition switch.

Thanks in advance,

jib

Lance,

Thanks for the quick response.

I have those drawings in front of me, as well as the PCB layouts, but I couldn’t convince myself that it was a low amp draw. I got uneasy when the switched feed disappeared into the relay on the MSpower.top, board layer 1 schematic. The path for X2 does not show up on the schematic – at least not to my untrained eye. Given the size of the solder pad for the switched circuit, I was concerned that I would be letting the smoke out of my ignition switch.

I think I need to take a short break and walk though the schematics until I am completely comfortable with them. I still (obviously) have a lot to learn.

Thanks,

Jib, backing up to take a running start (again) <grin>

Now I feel really stupid! X2 comes in to the board and becomes 12S. I didn't realize what that symbology meant. Now it’s obvious that when 12S in energized, the ECU relay pulls in and connects the 12U, powering up the MS. Duhhhh!

The rest of the diagram becomes much clearer now also. I don't know how I missed somthing this simple.

Thanks,

Jack

so where - in the car - are you guys pulling the switched 12V from?