Preventive maintenance of aerial work platforms: schedule by hours, the most common faults and the cost of downtime

In short: an aerial work platform needs four levels of maintenance: the operator’s daily pre-start check, the frequent inspection every 3 months or 150 hours by a mechanic, the annual inspection (no later than 13 months) by a technician qualified on the model, and an extraordinary verification after an accident, repair or long stop. The faults that stop the most machines in Portugal are batteries, joysticks and controls, tilt and load sensors, and hydraulic leaks. Almost all of them are avoided with distilled water, daily charging, cleaning and a five-minute visual check.

Why preventive maintenance pays

An aerial platform does not break down suddenly. It breaks down because nobody noticed the signs. JLG estimates that badly treated batteries last about a year and well treated ones three years or more: the difference is distilled water, a charger plugged in every night and ten minutes of cleaning a month. The same goes for the rest of the machine.

Maintenance and verification are different things, and the law requires both. Maintenance repairs and replaces; periodic verification assesses the safety condition and produces the report required by Decree-Law 50/2005. We cover the legal side in our guide to mandatory inspections; this guide is about the practical side: what to do, when, and what happens when it is not done.

The plan: four levels

The calendar below is what manufacturers require in their service manuals and what ISO 18893 recommends. JLG sums it up as three inspections: pre-start, frequent and annual. In harsh environments, with dust, salt, concrete or two-shift work, the intervals get shorter.

Every day, before starting

By the operator, at the start of the day, at shift change and whenever the operator changes. Five to ten minutes:

• Leaks on the ground under the machine and on visible cylinders and hoses.
• Hydraulic oil level and, on diesels, engine oil, coolant and fuel.
• Tyres: cuts, wear, rims, pressure on pneumatic tyres.
• Structure: cracks, deformation, pins and retainers in place.
• Platform: guardrails, gate, deck, anchor points.
• Legible decals and the manual in its box.
• Batteries: state of charge and, weekly, water level.
• Function test in a clear area: every function from the ground and the platform, emergency stop, emergency lowering, horn, alarms.

If anything fails, the machine does not work until it is repaired. The rule sounds obvious, but it is the one most often broken.

Every 3 months or 150 hours

By a qualified mechanic, whichever comes first, and also whenever the machine has been idle for more than three months or has just been bought second-hand:

• Batteries: specific gravity or voltage per cell, terminals, cables, charger.
• Hydraulic system: leaks, hose condition, oil level and appearance, drift test with the platform raised.
• Controls: joysticks return to neutral, enable switches, emergency stop buttons.
• Safety systems: tilt alarm and cut-out, load limiter, pothole protection, limit switches.
• Structure and wear: pins, bushings, boom wear pads, extension chain or cables, slew bearing bolts.
• Brakes, steering, oscillating axle.
• Lubrication of every point listed in the manual.
• On diesels: air, oil and fuel filters, belts, cold start.

Every year, no later than every 13 months

By a technician qualified on the specific model. JLG recommends a factory-trained technician and organises the annual inspection into eight areas: functions and controls, platform, scissor stack or boom, chassis, power system, hydraulic and electrical systems, manuals and decals, and general items such as unauthorised modifications, structural welds and lubrication. It is also the natural moment for the periodic verification with report required by law, and for replacing the hydraulic oil and filters at the intervals given in the model’s manual, usually every one to two years.

Extraordinary verification

After an accident, contact with a structure, an overload, a structural repair, a modification or a long stop. The machine does not return to work without it.

The most common faults, by system

This list comes from what we see on the machines we repair and inspect in Portugal. For each fault we give the symptoms, the usual cause, the part that normally fixes it and how to avoid it.

Batteries and chargers (electric machines)

• Symptoms: ever shorter range, a machine that will not last the shift, a charger with a red light or that never finishes its cycle, a low-battery code on the panel, slow motors when lifting.
• Causes: low water in the cells (the plates are exposed and lose capacity irreversibly), sulphation from sitting discharged or below 80% for days, batteries of different ages in the same set, corroded terminals, a faulty or misadjusted charger.
• Part: a complete set of traction batteries (replace all, never just one), charger, cables and terminals.
• Prevention: top up with distilled water after charging, never before; charge every night, even with little use; never store the machine discharged; clean the tops of the batteries every month, because dirt conducts and drains them; check the charger’s output voltage at the frequent inspection.

Request JLG batteries, chargers or cables · Other brands

Joysticks, controls and buttons

• Symptoms: a function that only responds on the second try, jerky movement, a joystick that does not return to centre, a control fault code at power-up, a machine that will not start from the platform but starts from the ground.
• Causes: mechanical wear of the joystick, moisture and dirt inside the control box, a crushed platform cable with broken wires, a worn enable switch, an emergency button with oxidised contacts.
• Part: joystick, enable switch, emergency stop button, platform control cable, complete control box.
• Prevention: cover the control box when the machine stays outdoors, do not pressure-wash the controls, route the platform cable along its original path, replace the joystick at the first sign instead of waiting for the machine to get stuck at height.

Request JLG joysticks and controls

Sensors: tilt, load, pothole and limit switches

• Symptoms: tilt alarm on a perfectly level floor, a machine that refuses to lift for no apparent reason, an overload message with an empty platform, a calibration code on the panel, pothole protection that does not retract.
• Causes: tilt sensor out of calibration after a knock or a replacement, load sensing system out of calibration or damaged, oxidised or loose connector, broken limit switch, bent pothole bars.
• Part: tilt sensor, load cell or sensor, limit switch, wiring; often all that is needed is a recalibration with the manufacturer’s analyser.
• Prevention: never bridge a sensor to finish the day, because it is illegal and the next person on the machine does not know; recalibrate after any work on the structure; clean and protect the connectors.

Request JLG sensors

Hydraulics: cylinders, hoses and valves

• Symptoms: a platform that drifts down when parked (the drift test fails), leaks and oil on the floor, slow or jerky movements, a scored cylinder rod, a swollen or sweating hose, pump noise.
• Causes: worn cylinder seals, aged hoses or hoses rubbing on the structure, a holding or lowering valve with dirt in it, contaminated or watery oil, low level.
• Part: seal kit or complete cylinder, hose, valve, filter, hydraulic oil.
• Prevention: keep the oil clean and at level, which JLG considers the single maintenance task with the biggest impact on machine life; replace hoses at the first sign of cracks on the outside; run the drift test at every frequent inspection.

Request JLG cylinders, hoses and valves

Tyres, brakes and axles

• Symptoms: uneven wear, cuts down to the carcass, a machine that pulls to one side, a parking brake that lets the machine creep on a ramp, noise from the hubs.
• Causes: tyres at the end of their life, a bent rim, a misadjusted brake, bearings, play in the oscillating axle.
• Part: tyres (foam-filled, solid or non-marking depending on the machine), rims, brakes, bearings.
• Prevention: check the tyres daily, do not travel elevated on uneven ground, respect the wheel torque values at the frequent inspection.

Engine (diesel machines)

• Symptoms: hard cold start, blue or white smoke, loss of power, starter-battery warning, oil or diesel leaks.
• Causes: clogged filters, glow plugs, alternator, starter battery, injectors, belts.
• Part: air, oil and fuel filters, glow plugs, belts, alternator, starter battery.
• Prevention: follow the manual’s filter and oil intervals, use clean fuel, do not leave the machine idle for months without looking after the battery and the fuel.

Structure and wear parts

• Symptoms: play in the boom or scissor stack, metallic noise when lifting, uneven movement of the telescopic boom, play in the turntable rotation.
• Causes: worn boom wear pads, play in pins and bushings, misadjusted extension chain or cables, under-torqued slew bearing bolts.
• Part: wear pads, pins and bushings, chain, cables, slew bearing.
• Prevention: lubrication at the manual’s points and intervals, checking for play at every frequent inspection, replacing wear pads before they touch metal.

Decals, guardrails and manual

They do not stop the machine, but they stop it at an inspection: illegible capacity decals, a gate that does not close, a bent guardrail, a missing manual. They are cheap parts and one of the most common reasons for failing a periodic verification.

Fault codes: what to do

Modern platforms tell you what is wrong. JLG ES-series scissor lifts show a code on the platform panel, and the full diagnostic trouble codes (DTCs) are read with the manufacturer’s analyser or, on recent models, on the display. Three rules:

1. Write down the code before switching off, and what the machine was doing when it appeared. Many codes vanish on restart and come back the next day, with the machine at height.
2. Do not restart repeatedly to clear the fault. A battery, tilt or load code exists to protect whoever is on the platform.
3. Send us the code, the model and the serial number. In most cases we can tell you over the phone whether it is a part, a calibration or a connection, and what you need to bring to get the machine working again. JLG’s fault code page explains the system.

What downtime costs

Do the sums for your own situation, but the structure is always the same:

• The idle crew. Two workers waiting for a machine cost, in wages and charges alone, a few hundred euros a day. If the machine was the only way to reach the work, the job has stopped.
• The replacement rental. A rental scissor or boom lift costs, in Portugal, a few hundred euros a week, plus transport both ways, and it is not available the same day.
• The deadline. Contractual penalties, the client kept waiting, the crew working overtime to catch up.
• The emergency part. A part ordered in a hurry costs more in shipping than the same part ordered the week before, when the symptom appeared.

On the other side of the scale is the price of a joystick, a hose, a tilt sensor or a set of batteries, which in most cases is a fraction of a single day of downtime. That is the argument for two habits: repair at the first symptom, and keep a small stock of parts per machine.

What is worth keeping in stock

• Fuses and relays, emergency stop buttons and enable switches.
• One platform joystick per model.
• One tilt sensor per model.
• The hoses that suffer most on your model, and a seal kit for the lift cylinder.
• Hydraulic filters and, on diesels, air, oil and fuel filters and belts.
• A spare charger if you run several electric machines of the same model.
• Capacity and safety decals.

We will tell you exactly which part numbers match your model and serial number; ask us for the list through the JLG parts page or the multi-brand parts page.

Genuine or aftermarket parts?

For safety components and anything connected to the control system, sensors, joysticks, modules, use genuine parts: the machine was calibrated with them and the liability in an accident is yours. For consumables such as filters, tyres, batteries and hoses there are equivalent-quality alternatives that can make sense. Our quote always states the origin of each part so the choice is yours.

The maintenance log

Record every intervention with the date, the hour-meter reading, what was done, the parts and who did it. This log is what ACT asks for at an inspection, what the insurer asks for after an accident, and what makes a used machine worth more on the day you sell it. We explain what a buyer looks for in those records in the guide to buying a used platform.

How it works with us

At Trapézio de Prismas we carry out preventive maintenance, repairs and periodic inspections of JLG and other-brand aerial platforms, on site, in the warehouse or at the factory, anywhere in Portugal.

• A maintenance plan per machine, with the frequent checks and the annual inspection scheduled and a reminder before each deadline.
• Diagnosis of mechanical, hydraulic and electrical faults, with the manufacturer’s analyser for JLG machines.
• Genuine JLG parts and parts for Genie, Haulotte and other brands, identified by serial number.
• A written report of every intervention, for your maintenance log and for the periodic verification required by law.

Request a maintenance or repair proposal or send us your parts request. We answer the same day.