Sorry for the double posts, the other topic was getting too conversationally crowded and off the main subject. I'll try to ask a direct question about a piece of circuitry that failed on me.
In one image you see the solenoid actuator. In the case of the failed relay, it was the relay that controlled the "ignition" in the car (when you turn your key all the way for about a second and the starter turns and your car starts).
Probing the circuit shows the transistor on the isolator failed. The diagrams are correct - so yes, the mosfets are connected to the voltage of the car.
I assume something is happening during the car start cycle, but I dont know what, and perhaps Im wrong.
So the question is why did it fail, and how should I correct this circuitry to prevent failure again?
I read about hooking up a capacitor over the solenoid too... to reduce arcing. Thoughts?