The positive wire should be connected to the positive terminal, and the negative wire should be connected to the negative terminal. If the power source is a battery, it is important to make sure that the polarity is correct; otherwise, the valve will not work properly.
Solenoids don't usually have a polarity so reversing the the current results merely in a reversal of the magnetic flux. However, Solenoids operating from DC should always have a Diode connected opposite to the polarity of the supply to prevent the high voltage spike that will be generated at switch-off.
The simple answer is that polarity does not matter on solenoid valve coils. Typically, the lead wires will be the same color so you can connect the positive terminal to either of the two wires.
Does a solenoid have positive and negative? The magnetic field in a solenoid has a north pole, but the polarity of a solenoid valve does not matter. That's because the polarity induced in the core of the solenoid reverses if the current in the coil reverses, so the motion of the core is the same either way.
A typical starter solenoid has three connections at its terminals: One terminal is the “B” or battery terminal, which connects the Solenoid through the positive battery cable. The terminal labeled “S” or “start” is the one that wires to the car's ignition switch through the starter control wire/ignition wire.
First, the red one connects the starter solenoid to its positive terminal. This wire is usually live, so be careful when handling it. Then, a black or greenish-yellow cable connects the starter motor to the battery's negative terminal.
A starting solenoid typically has four terminals: two for the high current circuit and the other two for the low current terminals, which are connected to the inner coil and activate the high current device on the high power end.
Solenoids only operate in one direction. When the solenoid coil is energized , a fixed internal component (called the stop) becomes magnetized, thereby attracting a moving component (called the plunger ). This magnetic attraction creates a pulling motion, moving the plunger toward the stop.
The positive (red) wire usually is connected by solenoid points activated by a lower amp wire to prevent higher amps passing through key connect or push button.
The direction of the magnetic field will correlate to the handedness of the current going through the coil. Basically it doesn't matter how the solenoid is constructed, what matters is the orientation of the current going through it.
If the current in the coil facing you is flowing in clockwise direction then its the south pole. If the current is flowing in anti-clockwise direction, then its the north pole. This can be figured out using Right hand thumb rule.
If the direction of current is anti-clockwise, the end of the solenoid acts as a north pole and vice-versa.
An electric current passes through a solenoid, resulting in a magnetic field. When you wrap your right hand around the solenoid with your fingers in the direction of the conventional current, your thumb points in the direction of the magnetic north pole.
Note: The solenoid is a simple coil of wire with no directional components, so it can be simply be reversed in the circuit to create the magnetic field in the opposite direction, or you can reverse the direction of the current passing through the solenoid.
In the world of DC electronics, the accepted wiring convention is that the red wire carries the positive voltage, and the black is circuit ground. Usually the red is marked as + (plus) and the black is marked as – (minus).
Solenoid coil failure can be caused by a number of factors. Applying an incorrect voltage to the coil will cause it to fail and may cause the coil to burn out. Electrical surges or spikes may also damage the coil. Burnt out coils cannot be repaired and will need to be replaced.
Reversing Solenoids are used to control reversing motors such as those in winches in trailer tarp systems. Economic in that two solenoids come at the cost of one; saving money and space while providing a simpler wiring set up for your remote system.
The smaller terminals are typically iron bolts: Solenoid terminal S (or 50) is for the control wire connecting to the starter relay and ignition switch. If there is a 4th terminal, this can be terminal R (connects to a ballast resistor) or I (connects to the ignition coil) — this terminal is usually not used.
As a rule of thumb, a starter-mounted solenoid has three terminals. As illustrated in the wiring diagram, the red wire connects to the large battery terminal on the starter solenoid, the purple wire connects to the 'S' terminal on the solenoid, and the yellow wire connects to the 'R' terminal on the solenoid.