What a solenoid test tells you
A solenoid is an electromagnet — a coil of wire wrapped around a metal rod that creates a magnetic field when electricity flows through it. When it stops working, your car, washing machine, or sprinkler system stops responding to commands. Testing a solenoid means checking whether it receives power, whether that power creates the magnetic field it should, and whether the mechanical parts move when they're supposed to.
You can test a solenoid three ways: by listening and feeling for the click when power arrives, by measuring voltage with a multimeter, and by measuring resistance in the coil itself. Most solenoids fail because the coil burns out (resistance goes infinite), the plunger gets stuck (mechanical failure), or power never reaches it in the first place (wiring or control circuit problem). Knowing which one you're dealing with tells you whether to replace the solenoid, free up the plunger, or look upstream at the power supply.
Key Takeaways
- A working solenoid clicks or buzzes when power reaches it and the plunger moves smoothly in and out.
- Use a multimeter set to DC voltage to confirm power is actually arriving at the solenoid terminals.
- Measure resistance across the coil with the multimeter set to ohms; a dead solenoid reads infinite resistance or zero ohms.
- A solenoid that receives power but doesn't click, or clicks but doesn't move the plunger, usually has a stuck or broken mechanical part rather than an electrical failure.
- Always disconnect power or remove the battery before testing resistance, because the multimeter's internal battery can be damaged by live current.
Step 1: Listen and feel for the click
Before you pull out any tools, turn on the system and listen at the solenoid. A working solenoid makes a distinct click or buzzing sound when power reaches it — the plunger snaps into place. If you hear nothing, power is not reaching the coil. If you hear a click but the mechanism doesn't move (a valve stays closed, a starter doesn't turn), the solenoid is energizing but the plunger is stuck or the mechanical linkage is broken.
Place your fingertip lightly on the solenoid body while it's powered. You should feel a vibration or a slight magnetic pull. Do not touch the plunger rod itself if it's moving — it can pinch or cut. This tactile test is fast and often tells you whether the electrical part is working at all.
Step 2: Measure voltage at the solenoid terminals
Set your multimeter to DC voltage. Most automotive and appliance solenoids run on 12 volts DC, but check your equipment's manual — some run on 24 volts or AC. Locate the two terminals on the solenoid where the wires connect. These are usually small metal posts or spade connectors.
With the system powered on and the solenoid supposed to be energized, touch the multimeter's red probe to one terminal and the black probe to the other. You should see a voltage reading close to what the solenoid is rated for — typically 12 volts, 24 volts, or whatever the manual states. If the meter reads zero or very low voltage (more than a volt below the rating), power is not reaching the solenoid. Check the wiring, fuses, relays, and control switch upstream.
If the meter shows the correct voltage but the solenoid doesn't click, the coil itself is likely burned out. Move to Step 3 to confirm.
Step 3: Measure resistance in the coil
Disconnect power and remove the battery or unplug the device before measuring resistance. A multimeter's internal battery can be damaged if you measure resistance while live current is flowing through the circuit.
Set the multimeter to ohms (Ω). Touch the red probe to one solenoid terminal and the black probe to the other. A healthy solenoid coil typically reads between 2 and 30 ohms, depending on the solenoid's size and design — check your manual for the exact specification. If you see a reading in that range, the coil is intact. If the meter reads infinite resistance (often shown as "OL" for overload), the coil is open and the solenoid is dead. If it reads zero or very close to zero, the coil is shorted and also needs replacement.
Write down the resistance reading. If it's within the normal range but the solenoid still doesn't work when power is on, the problem is mechanical — the plunger is stuck or the linkage is broken — not electrical.
Step 4: Check for a stuck plunger
If the solenoid receives power and the coil resistance is normal, but the plunger doesn't move, the rod is usually stuck in place. This happens when dirt, corrosion, or dried lubricant binds the plunger inside the solenoid body. Tap the solenoid gently with a rubber mallet or the handle of a screwdriver while power is on. Sometimes the vibration and magnetic pull will free it.
If tapping doesn't work, you may need to disassemble the solenoid or replace it entirely, depending on the design. Some solenoids are sealed and cannot be serviced. Others have a removable plunger rod that you can clean and lubricate. Check whether your solenoid is designed to be opened — the manual or a parts diagram will show this.
Step 5: Test the control circuit if power doesn't reach the solenoid
If the multimeter shows zero voltage at the solenoid terminals, the problem is upstream in the control circuit. Start by checking the fuse or breaker that protects the solenoid circuit — a blown fuse is the most common cause. Replace it with one of the same amperage rating.
If the fuse is good, check the relay (if there is one) by listening for a click when the control switch is turned on. A relay is a small electromagnetic switch that sends power to the solenoid. If the relay doesn't click, it may be bad. If it clicks but the solenoid still gets no power, trace the wiring from the relay to the solenoid for loose connections, corrosion, or breaks. Use the multimeter on voltage mode to test each point along the path — you're looking for where the voltage drops to zero.
When to replace versus repair
Replace the solenoid if the coil resistance is infinite or zero, or if it receives the correct voltage but doesn't click. These are signs the coil is burned out and cannot be repaired. Most solenoids are inexpensive and designed to be replaced as a unit rather than serviced.
If the solenoid clicks but the plunger doesn't move, or if power doesn't reach it at all, the solenoid itself is usually fine — the problem is mechanical (stuck plunger) or electrical (wiring, fuse, relay, or control switch). Fixing these issues is often cheaper than replacing the solenoid. Use your multimeter readings to narrow down which part of the system is actually failing.
Frequently Asked Questions
What voltage should a solenoid read?
Most automotive solenoids run on 12 volts DC, but some are 24 volts or higher. Check your equipment manual for the rated voltage. When the solenoid is supposed to be energized, the multimeter should show a reading within about one volt of that rating. If it's significantly lower, there's a voltage drop in the wiring or power supply.
What does infinite resistance mean?
Infinite resistance (shown as "OL" on most multimeters) means the coil is open — the wire inside is broken or burned through, and no current can flow. The solenoid is dead and must be replaced. This is the most common failure mode for solenoids that have been in service for years.
Can I test a solenoid while it's still connected?
You can measure voltage while the solenoid is connected and powered on. Never measure resistance while power is on — the multimeter's internal battery can be damaged. Always disconnect power before switching the multimeter to ohms mode.
Why does my solenoid click but not work?
A click means the coil is energizing and the plunger is moving slightly, but the mechanical output (valve opening, starter turning, etc.) isn't happening. The plunger is usually stuck partway, or the linkage between the plunger and the mechanism is broken or disconnected. This is a mechanical problem, not an electrical one.
How do I know if it's the solenoid or the relay?
Use the multimeter to measure voltage at the solenoid terminals. If voltage is present, the relay is working and the solenoid is the problem. If no voltage reaches the solenoid, the relay, wiring, or control switch is the problem. Listen for a click at the relay when you turn on the control switch — if you hear it, the relay is working.