When you hook it up it only becomes a simple ohms law equation. You don't take into account coil inrush or inductance, because it doesn't matter in the example we are talking about. It gets more complicate when you have to take into a count reactance but that's not the situation here. Don't try to over complicate things. Any coil that is powered continuously has no reactance and since the current is not changing the inductance doesn't matter either. Because it's static. When you drive a coil in a PWM mode THEN it comes into play, when you release power on the coil from the driving device (be it mosfet, transistor or simple contact) the coils field collapses and induces a voltage that is a ratio of the number of turns in the coil and material in the coil and usually generates several hundred volts. (Don't believe me, take a regular relay connect the coil to 12v while holding the terminals and release one lead and you will get a shock). This is way more complicated than you are trying to make this.
as far as seafoam, never used the stuff I always just remove them and clean them.
Jeff
