Why is my maglock humming but not holding the door?
A humming maglock that lets the door pull open is one of the most common access control call-outs. The usual cause, and a step-by-step check for the others.
A maglock that hums but does not hold is usually being fed AC, or badly smoothed DC, instead of clean DC. Maglocks are DC devices, so AC on the coil makes them buzz and grip weakly; the other usual suspects are the wrong voltage setting, voltage drop on the cable, and an armature plate that cannot sit flat.
It is one of the most common access control call-outs, and it is quick to diagnose with a multimeter and five minutes at the door. Here is the order we would check things in.
Why is my maglock humming but not holding?
An electromagnetic lock is a coil that turns into a strong magnet when DC current flows through it, pulling the steel armature plate on the door flat against its face. With AC, the magnetic field rises and falls many times a second. You hear that as a hum, and the plate never gets the steady pull it needs, so the door can be pulled open.
The same thing can happen with a supply that is labelled DC but is poorly smoothed, or with a supply that is overloaded and cannot hold its voltage.
Check the power first
- Read the power supply label. Make sure the output that feeds the lock is DC, not AC. Panels and transformers often have both.
- Measure DC volts at the lock terminals with the door closed and the lock energised. Compare it with the voltage the lock is set for.
- Switch the meter to AC volts on the same terminals. A clear AC reading means AC or ripple is reaching the coil.
- Check the voltage setting. Many maglocks are dual-voltage and set with a jumper or by how they are wired. A lock set for 24 V and fed 12 V holds weakly; a lock set for 12 V and fed 24 V can overheat.
- Check the load on the supply. Add up everything on that output: locks, readers, sounders. An overloaded supply sags when everything is energised.
Then check the cable run
On a long run with thin cable, the voltage at the lock can be well below the voltage at the supply. That is why the measurement in step 2 is taken at the lock, under load, not at the panel. If it drops, use a heavier cable, move the supply closer to the door, or use a higher-voltage setting where the lock supports it.
Then the mechanics: armature plate and door
- The armature plate must be able to rock slightly on its mounting so it lies flat on the magnet. If the mounting bolt is overtightened or the plate is fixed rigidly, it touches at one edge only and the hold drops.
- Clean faces. Paint, rust, dirt or a sticker between the plate and the magnet reduce the grip. Look for an even contact mark across the whole face.
- Alignment. The plate should cover the magnet face fully when the door is shut.
- The door must close all the way. A weak door closer, a sagging hinge or a thick seal can leave a gap, and a maglock cannot pull a door shut from a distance.
Do not fix it by changing how the door releases
Maglocks are fail-safe: they release when power is removed, and they are normally tied to the fire alarm and to a request-to-exit device. When you replace the supply or rewire the lock, keep those releases working, test them before you leave, and follow your local fire code. If the door is on a fire route, check the setup with the authority that approves it. Fail-safe and fail-secure locks behave differently in a power cut, so plan each door with its fire strategy.
Make the next one easier to spot
A maglock that stops holding rarely announces itself. In teamzPass, held-open alerts tell you when a door that should be shut stays open, and every door event is kept in the audit trail, so a door that stops securing gets noticed. The Complete solution brings the door access terminal, wallet-ready readers and the cloud platform together, and installers can try it in the free partner sandbox. See the partner programme.
Frequently asked questions
Why does a maglock hum?
A maglock is a DC device. A steady hum or buzz usually means AC, or DC with a lot of ripple, is reaching the coil. Check that the power supply has a DC output and measure the AC voltage across the lock terminals.
Why is my maglock not holding the door?
The usual causes are the wrong supply (AC instead of DC), the wrong voltage setting for the lock, voltage drop on a long cable run, an armature plate that cannot sit flat on the magnet, dirty faces, or a door that does not close fully.
How do I test a maglock with a multimeter?
With the door closed and the lock energised, measure DC volts at the lock terminals and compare with the voltage the lock is set for. Then switch the meter to AC volts on the same terminals: a clear AC reading means AC or ripple is reaching the lock.
Can I wire a 24 V maglock to 12 V?
Only if the lock is dual-voltage and set for 12 V with its jumper or wiring. A lock set for 24 V and fed 12 V holds weakly; a lock set for 12 V and fed 24 V can overheat. Follow the lock’s documentation.
How does teamzPass help with doors that do not lock?
teamzPass raises held-open alerts when a door that should be shut stays open, and keeps every door event in the audit trail, so a door that stops securing gets noticed instead of discovered.
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