Resources // Diagnostics
Scissor lift will not lift or will not drive: a diagnostic walkthrough.
Start from the symptom, not the guess. Four common complaints, what each one usually means, what you can safely check yourself, and the point where diagnosis has to take over.
Before you start
A machine that refuses is often protecting itself
The single most useful idea when a scissor lift stops cooperating: these machines are designed to inhibit functions on purpose. Tilt sensing, pothole protection, load sensing, guardrail and gate interlocks, and the control station selector all gate what the machine will do. A lift that will not raise, or will not drive at height, is frequently working exactly as designed and telling you about a condition. Deciding whether you are looking at a protection or a failure is most of the job.
Two things make everything downstream faster. First, note exactly when the problem happens: cold or warm, raised or lowered, from the ground station or the platform, every time or intermittently. Second, get the model and serial off the data plate. The serial pins the configuration the machine was built with, which decides what the fault codes mean and which parts it actually takes.
Symptom first
Four complaints and what they usually mean
Dead deck, nothing happens
No response at either control station usually points at power rather than hydraulics: battery state, main disconnect, a blown fuse, or the emergency stop left pressed at one station. An emergency stop down at the ground station will make a perfectly healthy machine look dead from the platform.
It will not lift, or lifts weakly
Batteries under load are the first suspect on an electric machine, then the charger. After power, the chain runs lift solenoid, valve, then pump. Weak or partial lift that improves after charging is a power story; weak lift on a fully charged pack is a hydraulic one.
It will not drive
If it drives lowered but not raised, that is very likely a designed restriction rather than a fault. If it will not drive at all, look at brakes not releasing, a drive controller fault, or pothole protection that has not deployed and is inhibiting motion on purpose.
It drifts down on its own
Oil is passing something meant to hold it: a holding or counterbalance valve, a cylinder seal, or a control valve not fully closing. This is a load-holding function, so the machine comes out of service rather than onto a watch list. Drift does not improve with time.
What you can check
Safe checks at ground level
All of these are visual or at ground level, with the platform down and the machine parked. None require opening a component or working under a raised deck.
Battery and charger. Terminals clean and tight, cables undamaged, no swelling or leakage, and the charger actually completing a cycle rather than faulting out early. On a machine that sits between uses, a charger that has quietly stopped working is a common cause of a lift that seems to have failed suddenly.
Emergency stops and station selector. Check both stations. A pressed stop or a selector left on the wrong station accounts for a fair number of no-response calls.
Obvious leaks. Look under the machine and at the cylinder rods. A wet rod or a puddle where the machine parks is worth reporting precisely, because where it leaks narrows what it is.
Guardrails, gate, and pothole bars. Rails secure, gate closing and latching, pothole protection free to deploy and not fouled or bent. An interlock that cannot satisfy itself will inhibit the machine.
Anything bypassed. Tape on a switch, a zip tie holding something open, a silenced alarm. If you find one, that is the finding: the machine comes out of service and the bypass gets reported rather than reset.
The emergency lowering control is worth knowing the location of before you ever need it. It is a safety feature for getting a platform down, not a workaround for a machine that will not lift, and using it does not diagnose anything.
Where it hands off
Where diagnosis has to take over
Past the ground-level checks, the work needs instruments and access. Reading stored and active fault codes takes an analyzer and the service literature keyed to your serial. Confirming a suspect valve, cylinder, or contactor means testing it rather than swapping it, which is the difference between a repair and a parts bill. Anything requiring the platform elevated for access belongs to someone equipped to do it safely.
A code names a circuit, not a part. That is why "it threw a code, so we changed the part the code mentions" so often fails: the circuit has several ways to break and only one of them is the part in the description.
When you hand it off, send the model, the serial, a photo of the data plate, and the pattern you noticed. That combination is worth more than a long description of the symptom alone, and it frequently saves a trip. Repair and diagnostics starts there, and boom machines follow the same path through the boom lift repair process.
Questions
Diagnostic questions
My scissor lift will not lift at all. What is the first thing to check?
Battery state and charger output, in that order, before anything else. A deck that will not rise is far more often a power problem than a hydraulic one, and a battery pack that reads fine at rest can still collapse under load. If the machine lifts weakly, slowly, or only part way, that pattern points at power before it points at the pump.
The lift works from the ground controls but not the platform. What does that mean?
That the machine and its hydraulics are largely fine and the problem is in the platform control path: the station selector, the platform harness, a connector, or the footswitch. It is a genuinely useful observation, so tell whoever you call, because it eliminates a large part of the machine before anyone opens anything.
Is it safe to keep using a lift that drifts down slowly?
No. Drift means oil is passing something that is supposed to hold it, and it is a load-holding function, so it belongs in front of a technician rather than on a watch list. It also tends to get worse rather than better. Lower the machine, take it out of service, and get it looked at.
The machine beeps and refuses to drive when raised. Is it broken?
Often not. Most scissor lifts deliberately restrict or block drive at height, and pothole protection that has not deployed will inhibit driving on purpose. A machine refusing to do something at height is frequently the machine working correctly. The stored fault code, if there is one, is what separates a protection from a fault.
How much of this can I check myself?
The safe ones are visual and at ground level: battery condition and connections, charger behavior, obvious leaks, tire and wheel condition, whether the emergency lowering control is present and reachable, and whether anything has been taped, tied, or bypassed. Anything that needs the platform elevated, a component opened, or the machine energized in an unusual way is where diagnosis has to take over.
Start the intake
Send the plate and the symptom.
Model, serial, and a photo of the data plate get you the fastest, most accurate answer. We reply during shop hours, Monday to Friday, 7:00 AM to 4:30 PM Central.