These kinds of projects never go perfect the first time, especially for me. But not to be deterred, I just make Lemonade and move on.
The boards were wired correctly per my schematic, so that wasn't it. I used a different LED for testing that was less sensitive so when I put the correct ones in, the Water Temp light was dim and got brighter closer to the set threshold. I found my mistake and fixed the schematic to reflect the proper route. Best to just wire the piezo to the LED so they both get the same signal at the same time. Fixed.
Then, I had not really thought enough about how to attach the long wires that go to the sensors and the LEDs to the circuit board. The screw type terminals are not good for automotive use because they can loosen with vibration. So plan B was to solder everything down. Sounded feasible so that was how these boards were configured. In just a few days of testing, it became obvious that Plan B wasn't going to work. Stranded Hookup wire breaks at the solder joint too easily. I used to know that!
Plan C is to use soldered in Headers. Two pin ones for the LEDs and a 12 pin one for the main connector. Then, crimp on pins are used that lock into place when pushed in. We used hundreds of different cannon plugs, headers, etc with the same type of connections on C-130's, H3's, H53's, Hueys, and T-39s in the Air Force, so I know that vibration is NOT going to be a problem.
This is just one of the steps that are required when you do something like this mostly by yourself. Had I had an engineering team assembled, it would have gone smoother. New boards are on order, the connectors and everything else is already here, and I am anxiously awaiting the new boards.
That said, for months now I have had my prototype hooked up to my test engine and Start Kart. I find myself looking at the Charging LED to make sure I have the engine revved enough to charge the battery and feel just a little better knowing that if for some reason my oil pressure or water temp goes south, I will hear about it right away. I will be adding to my Start Kart document to add this feature as well. Update in another 10 days or so when the new boards get here.
