single pole contactor troubleshooting? single pole contactor not working.

Coil burns out due to water or high amperage
If water is present at the contactor coil when it is powered, the coil will short out.
You can determine if the coil is intact or open by measuring on both sides of the coil with a multimeter. Make sure the power is off to the coil, the wires are removed and test measuring electrical resistance in ohms. If the multimeter is reading OL, this stands for "open line" and means that the coil is burnt out. If electrical resistance is measured, the coil is usually intact. Compare the electrical resistance reading to a known resistance on a new contactor of the same ratings and compare if the electrical resistance is too high.