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Revision B December 2013
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4. Shorts, Grounding Faults, and Open Circuits
In control wiring, shorts can only occur when ''hot'' lines (lines connected directly to the battery)
come in contact with a ground. A short will either cause a fuse to blow, if there is a fuse, or burn
the wire off at its weakest point. Likely spots for shorts are switches, electrical strain reliefs,
electrical junction boxes, and a control cord which has been pinched or cut.
Grounding faults are much like shorts except they occur on the opposite side of the electrical
component. A ''ground fault'' will cause the coil in the motor solenoid switch to remain
energized. This type of failure can happen because switching is done in the ground wire due to
the construction of the motor solenoid switch (See 3 – Electrical Switches above). Likely spots
for “faults” are the same as the shorts – See above.
An ''open'' circuit is simply a break which prohibits current flow. Likely spots for ''open'' circuits
are the same as shorts- See Above.
5. Solenoid Coils
Coils are used in solenoid operated valves and start switches. Failures can be caused by
vibration, water, improper voltage, or corrosion. The best way to test a coil is with an ohmmeter.
The meter should read some value of ohms. An infinite reading means that the coil has an open
circuit. The reading between any lead on the coil and the ''can'' should be infinite unless there is
only one lead wire and the coil is grounded to the ''can''.
6. Electrical Polarity
Pump motors supplied with TMA’s can be used on either positive or negative ground
systems.
