Vehicle Lift Safety Locks: How They Work and What to Check

The mechanical safety locks are what hold a vehicle up — not the hydraulics. Hydraulic pressure raises the lift; the locks are what stop it coming down if a hose bursts or a seal fails. If you work under a vehicle that has not been lowered onto its locks, nothing but oil pressure is keeping it there.

How they work

Inside each column runs a toothed ladder. As the carriage rises, a spring-loaded latch rides over the teeth and drops into each one — the regular clicking you hear on the way up. To lower, the lift first raises slightly to take weight off the latch, the latch is released mechanically or by air, and the carriage descends.

Both columns have their own locks, and a synchronised lift engages both at the same height. A lift that locks at different heights on each side has a problem.

The one habit that matters

Raise the vehicle slightly above the height you want, then lower it onto the locks before anyone goes underneath. You should hear and feel it settle.

Technicians skip this because the lift seems perfectly stable where it stopped. It is — until it is not. The whole purpose of the lock is to cover a failure that gives no warning.

Daily checks

• Listen on the way up. Even, regular clicks from both columns. Silence from one side, or irregular clicking, means a latch is not engaging properly.
• Confirm engagement after lowering onto the locks — it should settle firmly, not creep.
• Watch for one side settling further than the other.
• Check the release works cleanly on both columns, without force.
• Look for obstruction in the ladder — debris, old grease, damaged teeth.

Arm restraints are a separate system

People conflate the two. Safety locks stop the carriage descending. Arm restraints stop the arms swinging once the vehicle is raised, usually via a toothed segment at the arm pivot that engages under load.

The test is simple: with a vehicle raised, an arm should not move by hand. If it does, the restraint is worn and the lift needs attention before it is used again. Worn restraints let a vehicle shift as weight transfers during work — see our guide to lift arms, pads and adaptors.

What stops a lock working

• Debris and old grease in the ladder, which is why bay cleanliness is a safety matter.
• Worn latch or teeth, from age or from lowering onto the locks carelessly.
• Weak or broken springs, so the latch no longer drops positively.
• Air release faults on air-released designs — a leak can hold the latch clear without anyone noticing.
• Seized linkage from corrosion.

All of these are routine maintenance items under PUWER, covered in our guide to lift care and maintenance.

If a lock is not engaging

Take the lift out of use and lock it off. This is not a fault to work around or to leave until the next service. Locks and arm restraints are among the first things a competent person examines, and a lock fault is the kind of finding that withdraws a lift from service immediately — see our guide to what happens after a defect finding.

Frequently asked questions

What holds a vehicle lift up?

The mechanical safety locks. Hydraulics raise the lift; the locks hold the load and cover a hydraulic failure.

Should I always lower onto the locks?

Yes, every time, before anyone goes underneath. Raise slightly past your working height and lower until it settles.

What does irregular clicking mean?

A latch is not engaging cleanly — debris in the ladder, a weak spring, or wear. Take the lift out of use and have it checked.

What is the difference between safety locks and arm restraints?

Locks stop the carriage descending. Arm restraints stop the arms swinging under load. Both are checked; they are different systems.

How do I test arm restraints?

With a vehicle raised, try to move an arm by hand. It should not move. If it does, the restraint is worn.

Supply, installation and support

We supply and install two-post, four-post and scissor lifts across the UK, to the manufacturer's instructions and BS 7980. Request a quote or get in touch and we will reply within one working day.