What a multimeter tells you about a solenoid
A solenoid is an electromagnet — a coil of wire that creates a magnetic field when electricity runs through it. A multimeter can measure two things that tell you whether a solenoid is working: the resistance of the coil itself, and whether electricity can flow through it at all. These two measurements catch most solenoid failures before they cause bigger problems.
A solenoid fails in two main ways. The coil can burn out — the wire insulation melts or the wire breaks — which shows up as infinite resistance or an open circuit. Or the coil can short, meaning the wire touches itself where it shouldn't, which shows up as resistance that is too low. A multimeter catches both.
You do not need to understand electricity deeply to use a multimeter for this test. You need to know which dial setting to use, where to touch the probes, and what number to expect. This guide covers all three.
Key Takeaways
- Set your multimeter to the resistance setting (marked Ω or ohms) before you test, and make sure the solenoid is disconnected from power.
- Touch one probe to each terminal of the solenoid coil and read the number on the display — most solenoids show between 5 and 50 ohms when they are working.
- A reading of zero or very close to zero usually means the coil has shorted and the solenoid needs replacement.
- A reading of infinity (often shown as "OL" on the display) means the coil is open or broken and the solenoid cannot work.
- If your reading is within the normal range for that solenoid, the coil itself is probably fine and the problem lies elsewhere in the circuit.
Disconnect power and locate the solenoid terminals
Before you touch a multimeter to anything, make sure the solenoid is not powered. If it is part of a larger machine or vehicle, turn off the ignition or unplug the device. Wait a few seconds — some solenoids hold a charge. If you are not certain the power is off, use the multimeter itself to check: set it to voltage mode and touch the probes to the solenoid terminals. If the display shows zero, power is off.
A solenoid has two terminals where wires connect — these are the points you will test. On a car starter solenoid, they are usually large bolts. On a smaller solenoid like one in a washing machine or sprinkler valve, they may be small metal pins or spade connectors. Look for where the wires attach. If wires are soldered on, you may need to desolder them first or test through the solder joint itself.
If the solenoid is still mounted in a machine, you do not have to remove it. You can test it in place as long as you can reach both terminals with the multimeter probes.
Set the multimeter to resistance and touch the probes
Turn the dial on your multimeter to the resistance setting. This is marked with the Greek letter Ω (omega) or the word "ohms". If your multimeter has multiple resistance ranges — usually labeled 200Ω, 2kΩ, 20kΩ — start with the 200Ω setting. This range works for most solenoids.
Touch the red probe to one terminal and the black probe to the other. The order does not matter for resistance — you will get the same reading either way. Hold the probes steady for a second or two while the multimeter takes the measurement. Do not let the probes touch each other or touch any metal part of the solenoid body, only the two terminals.
Read the number on the display. Write it down. This is your resistance reading in ohms.
Interpret the resistance reading
Most working solenoids show a resistance between 5 and 50 ohms, though this varies by the solenoid's size and design. A car starter solenoid might read 0.5 to 2 ohms because it is designed to carry heavy current. A small solenoid in an appliance might read 20 to 100 ohms. If you have the solenoid's part number, you can search for its datasheet online to find the expected resistance range — this is the most reliable way to know if your reading is normal.
If you do not have a datasheet, use this rule: if the reading is a small number (anywhere from 0.1 to 100 ohms) and it is not zero, the coil is probably intact. If the reading is exactly zero or very close to it — like 0.0 or 0.1 — the coil has likely shorted and the solenoid should be replaced.
If the display shows "OL" (open line) or infinity, the coil is broken or open. No current can flow through it, and the solenoid cannot work. This also means replacement is needed.
What to do if the resistance is normal
A normal resistance reading means the coil itself is not burned out or shorted. If the solenoid is not working despite a normal resistance reading, the problem is elsewhere: the power supply might be failing, the wiring might be broken, or the solenoid might be mechanically stuck even though the coil is fine.
Test the power supply next. Set your multimeter to voltage mode and check whether power is actually reaching the solenoid terminals when the circuit is turned on. If power is there and the resistance is normal but the solenoid still does not click or move, the solenoid itself may be mechanically jammed or the electromagnet may be too weak to overcome friction — both of which require replacement.
What to do if the resistance is abnormal
If the reading is zero or very close to zero, the coil has shorted. This usually happens because the wire insulation has melted or worn through, allowing the coil to touch itself. A shorted solenoid draws too much current and will overheat or blow a fuse. Do not keep using it — replace the solenoid.
If the reading is infinity or "OL", the coil is open. The wire has broken somewhere inside the coil, or a connection has failed. An open solenoid will not work at all and cannot be repaired by rewinding — replacement is the only option. Some people attempt to rewind a solenoid coil, but this requires precision equipment and rarely works as well as a new part.
Common mistakes when testing a solenoid
The most common mistake is testing a solenoid while it is still powered. This can damage the multimeter or give a false reading. Always disconnect power first and wait a moment before testing.
Another mistake is testing through corroded or dirty terminals. If the terminals are covered in rust or corrosion, clean them with a wire brush or fine sandpaper before testing. Corrosion can block the electrical contact and give you a false infinity reading even though the solenoid is fine.
A third mistake is using the wrong multimeter setting. If you set the dial to voltage or current instead of resistance, you will get a meaningless reading or damage the multimeter. Always check the dial before you touch the probes to anything.
Finally, do not assume a normal resistance reading means the solenoid will work. Resistance only tells you the coil is intact. It does not tell you whether the electromagnet is strong enough to do its job, whether the mechanical parts move freely, or whether power is actually reaching it. A normal resistance reading is a good sign, but it is not a may provide.
Frequently Asked Questions
Can I test a solenoid while it is still connected to the machine?
Yes, as long as the power is off and you can reach both terminals with the multimeter probes. You do not have to remove the solenoid from the machine to test its coil resistance. However, if other components are also connected to those terminals, they may affect the reading, so disconnecting the solenoid is more reliable if you have the time.
What does it mean if the multimeter shows different readings each time I test?
Fluctuating readings usually mean the probes are not making solid contact with the terminals. Clean the terminals and try again, pressing the probes firmly against them. If the reading still jumps around, the solenoid may have an intermittent break in the coil, which is a sign it should be replaced soon.
Is a solenoid with high resistance still usable?
It depends on how high. If the resistance is much higher than the solenoid's design specification, it will not pull in or work properly because not enough current can flow. Check the datasheet if you have it. If the resistance is only slightly high and the solenoid still works, it may just be aging, but it will eventually fail.
Can I fix a shorted solenoid by drying it out?
No. A short means the wire insulation has failed or the coil has physically touched itself. Drying will not repair the insulation or separate the wires. A shorted solenoid must be replaced.
What if I cannot find the solenoid's expected resistance range?
Use the zero-or-infinity rule: if the reading is any small number and not zero, the coil is probably fine. If it reads zero or infinity, the solenoid needs replacement. This is not perfect, but it catches the most common failures. You can also test a known-good solenoid of the same type to compare.