A solenoid, often referred to as a switch, is normally activated manually or mechanically i.e. key switch. Solenoids switches are activated by external electrical input. A solenoid is used to break an electrical circuit, or make one. Some folks call a solenoid “a contactor”.
There are two basic circuits to a solenoid. Primary and Secondary. The primary, also referred to as activation circuit, has both activation wiring and an internal primary coil. With electrical voltage, the internal primary coil activates and brings two contact points together to allow an electric current to come through the secondary circuit. That coil requires a + and – potential for electric voltage to pass through and activate it. Most golf carts activate the soelnoid with normal battery pack volts. However, some older cars that use tapped voltage, and the solenoid must be connected to a specific voltage. Taps are connecting points on a battery pack. The power circuit aka secondary circuit is the circuit being activated by the solenoid coil. This circuit has large power contacts inside the solenoid switch that allow heavy load of electric current to flow to the motor or a starter generator when activated. Be sure to have the correct wiring diagram for the test.
1. Does the solenoid make a clicking noise? If it doesn’t, we need to determine if activation voltage is present at the small terminals. Connect a voltmeter across the small posts and activate the system. Caution safety: Raise rear wheels off the ground and use stands BEFORE you test as car may lunge forward so be cautious. Put the car in run mode and key switch on, car in forward and accelerator pedal pushed. If voltmeter displays system voltage and solenoid does not click, solenoid is defective and needs to be replaced.
2. The solenoid does not click and you do not read system voltage, this tells us one of the voltage potentials is ‘mia’ at one of the two connections. To find out which one is missing, leave the red lead of voltmeter connected to terminal 2, the positive connection (usually blue or red wire). However wire colors may vary! Use correct diagram for your make and model year for correct diagnoisis. Place black lead of voltmeter to battery’s negative post on the No. 6 battery (last in the series from the first positive battery connection). Activate system, if voltmeter reads system voltage, the positive input is correct. Meaning key switches, micro switches & wiring are good & you are missing negative input.
3. Positive connection at Terminal 1: Continue the diagnosis by connecting the black negative lead from voltmeter to teriminal No. 1, and the red lead of voltmeter to battery No. 1’s positive post (first positive connection to the car). Activate system again. If you are not reading system voltage on your voltmeter, you’ve confirmed the battery negative is missing. Depending on the system the car is using, the missing negative will need to be traced to the source. Some systems supply negative from a controller output (some Club Cars, the onboard computer) Most gas cars use the frame as ground. Electric cars do not use a frame ground. Determined by using correct wiring diagram.
4. Negative connection at Terminal 1. If we are missing the positive at connection terminal No. 2, it means the key switch, micro switch and or accelerator switch is open or out of adjustment. Please note: Some cars use the key circuit as a negative circuit & adjust accordingly per correct wiring diagram. Trace voltage to each component in that circuit & determine where voltage is lost. If your car uses the diode in the solenoid system, be sure you make proper connections as the diode is polarity sensitive.