What a multimeter tells you about a solenoid
A solenoid is an electromagnet — a coil of wire that creates a magnetic field when electricity flows through it. A multimeter can measure two things that tell you whether a solenoid is working: the resistance of the coil itself, and whether voltage is reaching it. A solenoid that reads infinite resistance (the needle doesn't move, or the display shows "OL") has a broken wire inside. A solenoid that reads zero or near-zero resistance may have a short circuit. If voltage reaches the solenoid but it doesn't click or move, the coil is likely dead.
Most solenoids sit in cars, washing machines, irrigation systems, or door locks. The test is the same for all of them: you measure resistance when power is off, and voltage when power is on. This tells you whether to replace the solenoid or look for a wiring problem instead.
Key Takeaways
- Always disconnect power and remove the solenoid from the circuit before measuring resistance, or you will damage the multimeter.
- Infinite resistance (OL on the display) means the coil wire is broken and the solenoid cannot work.
- Zero or very low resistance (under 1 ohm) suggests an internal short circuit, and the solenoid should be replaced.
- Normal resistance varies by solenoid type — check the manufacturer's spec sheet or the label on the part itself for the expected range.
- If resistance is normal but the solenoid doesn't respond, measure voltage at the terminals while power is on to confirm electricity is reaching it.
How to measure solenoid resistance
Turn off all power to the circuit. Unplug the device or switch off the breaker. Wait a few seconds to let any stored charge drain. Then physically remove the solenoid from the circuit — disconnect the wires or unscrew it from its mounting.
Set your multimeter to the resistance setting, marked with the ohm symbol (Ω). If your meter has multiple resistance ranges, start with the lowest one (usually 200 ohms). Touch one probe to each terminal of the solenoid. The meter will display a number. Write it down. If the display shows "OL" or "1" with no decimal, the coil is open (broken). If it shows 0 or 0.1, there is likely a short inside.
Compare your reading to the solenoid's specification. Most solenoids read between 5 and 100 ohms, but this varies widely. Look for a label on the solenoid itself, or search the part number online. If your reading is wildly different from the spec — much higher or much lower — the solenoid is faulty.
How to measure voltage reaching the solenoid
This test tells you whether electricity is actually getting to the solenoid. Reconnect the solenoid to the circuit, but do not power it on yet. Set your multimeter to the voltage setting (marked with a V, usually DC voltage). Touch one probe to the negative terminal of the solenoid and one to the positive. Now turn on power.
The meter should display a voltage close to what the solenoid is rated for — usually 12 volts, 24 volts, or 120 volts depending on the system. If the display shows zero, power is not reaching the solenoid. Check the wiring, connectors, and any switches or relays in the circuit. If voltage is present but the solenoid does not click or move, the coil itself is dead and needs replacement.
Turn off power immediately after the test. Do not leave the solenoid energized while you are troubleshooting, as it will heat up and may burn out.
Reading the multimeter display correctly
Digital multimeters show numbers on a screen. Analog multimeters have a needle that moves across a scale. Both can measure solenoids, but they work differently. On a digital meter, "OL" means the resistance is too high to measure — the circuit is open. On an analog meter, the needle stays at the far left (zero current) when the circuit is open.
If you are using an analog meter and the needle jumps to the far right immediately, stop the test. This usually means you have the probes reversed or the meter is set to the wrong range. Switch to a higher resistance range and try again. Digital meters will not be damaged by reversed probes, but analog meters can be.
Common mistakes that damage the multimeter
The most common error is measuring resistance while power is on. This sends electricity backward through the meter and can destroy it. Always turn off power and disconnect the solenoid before measuring resistance. The second mistake is measuring resistance on a solenoid that is still connected to the circuit. Even with power off, other components in the circuit can affect the reading or damage the meter. Disconnect the solenoid completely.
A third mistake is touching the metal probes to your skin while testing. This creates a parallel path for electricity and gives a false reading. Hold the probes by the plastic handles only. If you are testing a solenoid in a tight space, use probe clips or alligator clips to hold the probes steady instead of your fingers.
When to replace the solenoid versus troubleshooting the circuit
If resistance is normal but voltage is zero, the problem is in the wiring or control circuit, not the solenoid. Check for loose connectors, broken wires, blown fuses, or a failed relay or switch. If resistance is abnormal (very high or very low), the solenoid is faulty and replacement is the fastest fix.
If resistance is normal and voltage is present but the solenoid does not respond, try a different test: measure voltage again while someone activates the switch or control that should trigger the solenoid. If voltage appears only when the switch is activated, the solenoid coil is likely dead. If voltage is always present, the solenoid may be mechanically stuck or the plunger may be jammed. Try tapping it gently with a rubber mallet. If it still does not move, replace it.
Solenoid resistance ranges by type
Automotive starter solenoids typically read 0.5 to 2 ohms because they carry very high current. Door lock solenoids usually read 20 to 50 ohms. Irrigation valve solenoids often read 30 to 100 ohms. Washing machine solenoids vary widely depending on voltage — 120-volt models may read 200 to 500 ohms, while 24-volt models read 10 to 50 ohms.
The safest approach is to look up the part number on the solenoid and find the manufacturer's data sheet. If you cannot find the spec, compare your reading to a known-good solenoid of the same type. If you have no reference, a reading that is not zero, not infinite, and not wildly different from other similar parts is usually acceptable. The resistance test is mainly useful for catching obviously broken coils.
Frequently Asked Questions
Can I test a solenoid without removing it from the circuit?
You can measure voltage without removing it, but you should not measure resistance while it is connected. Other components in the circuit will affect the resistance reading and may damage the multimeter. Disconnect the solenoid first, measure resistance, then reconnect it to test voltage.
What does it mean if the solenoid reads 0 ohms?
Zero ohms means there is a direct short circuit inside the coil — the wire insulation has failed and the coil is touching itself. The solenoid cannot work and should be replaced. Do not try to use it, as it will draw excessive current and may overheat or catch fire.
Why does my solenoid have normal resistance but still does not work?
The coil may be fine but the plunger inside may be stuck, or the mechanical linkage may be jammed. Try tapping the solenoid gently with a rubber mallet. If that does not help, measure voltage while the solenoid is powered on to confirm electricity is reaching it. If voltage is present and the solenoid is still silent, the coil is likely dead despite the resistance reading.
Do I need a special multimeter to test a solenoid?
No. Any standard digital or analog multimeter can measure resistance and voltage. You do not need an expensive meter or one with special features. A basic meter from a hardware store works fine for solenoid testing.
What voltage should I expect to see when testing a solenoid?
That depends on the system. Automotive solenoids usually see 12 volts. Irrigation and industrial solenoids often see 24 volts. Household appliances may see 120 volts AC. Check the label on the solenoid or the device manual to find the rated voltage, then expect to see close to that number when the solenoid is powered on.