What Is A Solenoid In A Golf Cart? (And What Does It Do?)


Many golf cart enthusiasts have had solenoid issues and experienced downtime because of them. Understanding what a solenoid is in a golf cart is vital for troubleshooting and repair.

What is a solenoid in a golf cart? A golf cart solenoid is a relay, a remote-controlled high-amperage relay designed to protect the delicate contacts in key switches, buttons, etc. from the high-temperature arc of electricity. A golf cart solenoid provides forward and reverse functions in some golf carts.

What Are The Symptoms Of A Bad Solenoid?

  1. The first and most obvious symptom is the golf cart won’t start. If it is a gas-powered cart, the engine doesn’t turn over, and if it is an electric cart, the cart doesn’t move. Now, on to the next symptoms…
  2. The engine on the gas-powered cart starts, but the starter doesn’t disengage after starting. When the contacts weld together, the power to the starter never stops and will result in destroying the starter, the wiring, or the flywheel.
  3. The relay clicks and works sometimes, and sometimes it doesn’t. This can be a faulty wire connection, but can also mean the solenoid is beginning to fail.
  4. The golf cart solenoid doesn’t click when the accelerator is pressed. This again can be faulty wiring or a failed solenoid.
  5. The golf cart solenoid clicks, but nothing happens. This will sometimes be the result of burned contacts or contacts no longer coming in contact with each other as shown in the illustration at the bottom of this page. This can also be the result of not enough voltage amps reaching the solenoid control connection due to a low battery.

How to Test A Golf Cart Solenoid Diode

Some of the late model golf cart solenoids have a diode attached across the terminals. A diode allows current to run in one direction, but not in the other. Testing the diode is a simple procedure. Remove the diode from the circuit and check the leads with a continuity tester.  Reverse the leads and test again. The connection to the light or buzzer should complete in one direction, but not when tested the other direction. If continuity is present in both directions, or no continuity in both directions, the diode is bad.

A Story

It is not always the solenoid…even though it gets blamed most of the time. My brother called me the other day because his EzGo suddenly stopped moving, about 10 feet from his driveway. He pushed it to safety and thought he would need to replace the solenoid. He said he smelled something like sulfur and heard a sizzling sound. Solenoids are sealed, so the smell was probably not the solenoid.

I came over and raised the seat, and after switching the tow switch on, I checked the battery terminals first. There was yellow corrosion and they needed a good cleaning. After re-attaching the battery cables and turning the tow switch back off, the cart was back to its old self again. We took it out for a test run and all was good. 

There was no click from the solenoid, but it was because there was no power coming from the battery due to all the corrosion and gunk.

Now, let’s assume you aren’t as lucky as he was. Here are some key steps for diagnosing the REAL problem.

Tools Needed

  • A Multimeter or Voltmeter
  •  2 Wenches – usually a ½” or similar
  • Gloves
  • Electrical Tape
  • Safety glasses

How A Solenoid Works

A solenoid is NOT an electromagnet, but it IS a coil of wire, partially surrounding an iron core, that is made to move inside the coil by the magnetic field caused by current flowing through the coil. It is used to convert electrical energy to mechanical energy, as in the operation of a switch. This coil BECOMES an electromagnet when the electricity is applied to it. When energized, the magnetic field pulls the plunger or rod into the coil and the plate attached to it snaps up against the internal contacts. This bridges a circuit and sends the high voltage current on to the motor or controller. A spring returns the plunger back to its original position when the circuit is switched off.

How A Solenoid Is Used

Single and Dual Types – Older Electric Carts

In the early 1960s, a bank of solenoids was used in electric carts to redirect electrical power of different voltages, or through a resistor, to vary the speed of the electric motor. The number of single-action solenoids used in each golf cart was reduced with the advent of dual-action solenoids.

A good example of a solenoid bank can be seen in the illustration below:..

Using various combinations of the above solenoids, the current was redirected to the motor either with two banks of 18 volts in parallel and then through a resistor producing a low speed. The current could then be redirected to bypass the resistor, producing a higher speed. A different combination would put two banks of 18 volts in series, producing 36 volts for yet another speed…and so on.

Solenoid Cutaway

Key to the Illustration Above

  1. Low voltage terminals. These terminal posts represent each end of the wire coil winding around the metal movable core.
  2. Movable Core. This slides up toward the electromagnetic field caused by applying the voltage to terminals #1.
  3. Wire Coil. This is the part  of the solenoid that becomes electromagnetic when the low voltage is applied to terminals #1
  4. Large Terminals.  When the core #2 travels up into the coil #3, the plate on the bottom contacts the two terminals (shown in dashed lines) and makes a bridge for the current to flow through the solenoid
  5. Lower Large Terminals. In a double-action solenoid, the Lower terminals are bridged and passing along current while the solenoid is not energized. The contact is broken when the plate moves up to contact and bridge the side terminals #4.
Physical Image of A Double Action Solenoid
Later Model Solenoid for an EzGo Golf Cart

Newer Electric Golf Carts

Advancements in technology allowed for the variation in motor speed to be achieved through an electronic controller. A single solenoid is now used to direct power to the controller and the controller is in turn regulated by a combination of a microswitch and a stepping potentiometer.

An example of in-cart testing is the E-Z-GO Series Drive system. The solenoid test is done with the resistor removed from one large terminal. You should always have voltage (+) on the side connected to the batteries. When the small terminals have both positive and negative voltage applied to them the solenoid should CLICK and full battery voltage should be present at both large terminals. If not, then the solenoid is faulty. If the positive and negative voltage is not present at the small terminals when the pedal is pressed, a problem exists within the solenoid activation circuit. Tracing back on this circuit is fairly simple using a wiring diagram. The switches are activated in order: Reed switch, Forward and Reverse micro switch, key switch, Foot or pedal box switch. All of these switches must be working before the activation is delivered to one of the small posts (red wire).

Starter Solenoid – Gas Carts

Automotive and gas-powered golf carts use variations of the illustration on the left. Power is applied to the solenoid low-voltage terminals, and the piston travels back, simultaneously bridging the contacts to the starter motor and pulling back on the lever to engage the pinion gear.

On some models of golf carts, the starter is also the alternator and acts to charge the battery as the cart is driven.

Where To Find The Solenoids

In all golf carts, new and old, the solenoids can be found under the seat or in the engine well and are easily identifiable by the wires that lead to them. Banks of solenoids, as in the previous illustration, are mounted on the side or back panel near the electric motor. On gas motors, they will be attached to the large starter/alternator bolted to the engine.
On newer electric golf carts, an EzGo for example, the solenoid has its own compartment under the seat and is accessed by removing a protective cover.

Troubleshooting

Testing the Solenoid Without Removal from Cart

BEFORE testing the golf cart solenoid, test both the accelerator micro switch and the key switch. These components are both wired into the control circuit of the solenoid and if they are faulty, the solenoid will not operate.

Turn the key switch on and press the accelerator. Do you hear a click? At this point, we still have to test the solenoid, but we know something…power is not activating the solenoid. With the pedal depressed, check the voltage at the small terminals of the solenoid. If there is no voltage, then the solenoid is NOT at fault. If there is a click, then…proceed to the next paragraph.

Disconnect the cables that go to the larger solenoid terminals. Use electrical tape to wrap the ends of the cable to prevent shorting them accidentally by connecting through a metal conducting object (like the frame of the golf cart) or touching each other. This will ensure the vehicle will not suddenly leave the premises while testing the solenoid.

With the key turned off and the cables disconnected, set the voltmeter to the ohms setting and touch each large terminal with the probes. There should be zero ohms. If the reading is not zero, then the solenoid is stuck and needs to be replaced.
If the ohmmeter does read zero, set the cart to forward travel and turn the key switch on. Press the accelerator pedal (or have a friend do it) and you should hear a click. If you don’t hear a click, measure the resistance anyway. If it now shows resistance, where there was none before, it should be under 0.4 ohms.

If you do hear a clicking sound, and the reading is fewer than 0.4 ohms, but not zero, the solenoid is good. If the reading is higher, the solenoid is bad and needs to be replaced.

To double-check the solenoid when you cannot hear a click from the solenoid and there is no resistance between the large terminals, set the voltmeter to DC volts using the 200 range. Turn the key switch on and take a reading on the smaller terminals while pressing on the accelerator. If there is no voltage, the problem is not with the solenoid. If it displays full voltage, then the solenoid is bad and should be replaced with a new one.

Bench Testing the Solenoid

Equipment needed to bench test:

  • 6v or 12v battery with leads long enough to go from battery post to solenoid terminal.
  • A battery-powered continuity tester (multimeter set to continuity will work)

On the double contact solenoids, check the bottom terminals for continuity. If the solenoid is not yet energized, these contacts should be closed and have a continuous circuit. On both single and double contact solenoids, the side terminals should be open and show no continuity in an unpowered state.
Apply 6-12v to the smaller terminals using the leads from the battery. You should be able to hear a click when energized. If you hear a click, check the large side terminals for continuity. You should find a continuous circuit. The bottom terminals should not have any continuity. If you do not hear a click, the solenoid is bad and must be replaced.

A common cause of failure in a solenoid is an improper loosening and tightening of the terminals. You must use TWO 1/2″ wrenches when attaching the cable on the large terminal posts…one to hold the nut closest to the solenoid body to prevent it from twisting inside the unit and the other to turn the outside nut.

 Below is an illustration of what happens when the contact is twisted and no longer aligned with the flat plane of the moving plate. The left side makes a minimum of surface contact and the right side can no longer make contact at all. The solenoid is now useless until you can line it back up again through trial and error because you cannot see inside.

Replacement

Ok, you have determined that you need to replace the solenoid. Many places carry replacements, like Amazon and eBay and run anywhere from $12 to $57 depending on the type. When you look for a replacement online, always have the make, model and year of your golf cart handy. Solenoids are fairly cheap and just think how much money you just saved diagnosing it yourself. If you are unsure of the model and year…Fear not..instructions are posted on this site that will help you identify your golf cart.

How to Bypass a Solenoid

Occasionally, troubleshooting the wiring system in your golf cart requires bridging the large terminals on your golf cart solenoid. I recommend doing this only for testing purposes and not as a permanent / semi-permanent fix for what ails your cart.

The following steps are troubleshooting procedures that lead up to actually bridging or jumping a solenoid. They will help you find out if the solenoid is bad before you go through the trouble.

Safety First

  • Raise the rear wheels off the ground using the proper support stands BEFORE you begin your solenoid testing.
  • Get a fire extinguisher and keep it handy. YouTube has a ton of golf cart fire videos and you don’t want to be one of them.
  • Higher voltage cars can cause severe burns and can occur by accidentally shorting out connections with metal objects.
  • Solenoid testing should be done in a well-ventilated area and extreme caution used around the batteries as hydrogen gas may be present. Flames and sparks can ignite these gases
  • Keep battery acid away from your skin and eyes as this can be an irritant.

For a gasoline-powered cart, using a jumper between the large terminals will bypass the key switch and will (if the solenoid is faulty) spin the starter/alternator when the accelerator pedal is pressed. Using a jumper wire (preferably with alligator clips on the ends) attach one end of the wire to one of the large terminals and cautiously brush the other end on the remaining large terminal. If it sparks, note if the starter engages. If there is no current present, attach the wire firmly on the large terminal bridging across and effectively bypassing the solenoid. With the key on, attempt pressing the accelerator and see if the starter engages.

If the starter does engage then the solenoid is either bad OR not receiving the control voltage to the small terminals. You will need to test the voltage across the small terminals to determine which case is true.

You can also remove the cables that are attached to the large terminals and join them together thereby bypassing the solenoid. It is easier to break the connection if you only need to yank the jumper off the contacts, so that is why I recommended it first.

If this is an electric cart, the solenoid is supplying the power to the controller and jumpering the large terminals will allow the pedal to rev the motor up to speed – provided the solenoid is the point of failure.

Conclusion

Solenoids are one of the cheaper components to replace on a golf cart, and it is a great idea to have at least one on hand in your work area. You can find a variety of replacement solenoids for your particular model on Amazon.

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