Why is the solenoid cylinder in the module getting hot?

The solenoid will become hot if the valve open check box is left checked. Normal valve openings are very brief and within a range of 10-1000 milliseconds, which does not cause the solenoid cylinder to get hot. If the Open Valves button is clicked or the Valve Open check box (in the GPM software screen) is checked, the valve is continuously held open. The software will limit the time to three minutes; however, it may still get hot. 

If using this function, be sure to start with a fully charged battery as the Valve Open function has a significant drain on the battery. As soon as there is no need to have the valve open, click the Close Valves button or uncheck the Valve Open check box to avoid unnecessary use of the solenoid and drain on the battery.