A bike that shows nothing at all — no display, no lights, no beep — is the fault where guessing costs the most. Owners buy a battery, then a controller, and find out afterwards that a fuse had blown or a plug had shaken loose. The power chain is short, and it can be walked in order. This checklist walks it the way the brands' own support documents do: free checks first, measurements second, parts last.
Before you touch anything
Switch the bike off, take the battery out, and wait thirty seconds. Working live on a motor or controller connector can arc and wreck the controller's output stage. Take the battery out again before you separate anything further down this list.
Stage 1: the free checks
Every brand support document we have compared starts here, and a large share of no-power bikes never get past this stage.
- Is the pack actually seated? Push it back into the cradle until it latches. A pack that looks home can still be a millimetre short of contact.
- Is the battery's own switch or key on? Many packs have a separate power button, and some have a keyed lock that cuts the output.
- Press the charge-level button on the pack. If its own LEDs will not light, the problem is inside the battery, not in the bike.
- Charge it until the charger's light turns green, then retry. A pack that has been sitting for months can be below the voltage its protection board will switch on at.
- Check the main battery-to-controller plug. Unplug it, look into both halves, and plug it back firmly. Loose or half-mated is the single most common finding.
- Find the fuse. Many bikes carry an inline fuse near the battery cradle. A blown one is a two-dollar part that reads exactly like a dead bike.
- Look at the cradle terminals. Green corrosion or black scorch marks around the contacts point to a bad connection that has been arcing under load.
Stage 2: measure, do not guess
If Stage 1 changed nothing, a multimeter turns the rest of this into ten minutes of work instead of a shopping trip.
Measure at the pack's discharge terminals. A charged 48V pack reads roughly 54.6V; a charged 36V pack reads roughly 42V. A reading of 0V, or one far below the nominal figure, points at the pack or its protection board rather than at the bike.
If the pack shows voltage, follow the loom forward. Measure again at the controller's input. Voltage at the pack but none at the controller means the break is in between: the plug, the fuse, or the cable itself. That single comparison is what separates a battery problem from a wiring problem, and it is the measurement most owners skip.
A word on the battery itself: we sell parts, not packs, and we do not recommend opening, rebuilding or paralleling lithium packs at home. If the measurements point inside the battery, take it to a service point with the equipment for it.
Stage 3: replace in this order
Cheapest and most likely first. This is the order the brand documents use for a bike that will not switch on:
- Fuse. Pennies, and it fails for a reason — if a new one blows again, stop and find the short.
- A known-good battery. Borrowing a pack that is known to work is a test, not a purchase. It settles the question in one minute.
- Display. On most bikes the power button lives on the display, so a dead display looks exactly like a dead bike. Check that the head-unit connector is clean and its pins are straight before you condemn it.
- Controller. Last, because it is the part people replace first and the part that is least often at fault here.
One caution on the display step: a display and a controller have to speak the same protocol, so a replacement that fits the plug can still leave you with a dark screen. Our guide on why a new display may not work with your controller covers what has to match.
Two nearby faults that are not this one
- Screen lights up, nothing drives. That is a different tree, and the first suspect is the brake cut-off rather than the motor. Start with our walkthrough of assist that has stopped working while the throttle still drives.
- Screen lights up with a code. Write the code down before anything else; it names the circuit for you. Many brands share the same numbering in the twenties, which we mapped in our guide to error codes 21 through 30.
Before you order a part
Four photographs answer nearly every fit question: the face of the display with its model marking, the display connector with its pins visible, the controller's label with its voltage and current ratings, and the motor cable where it leaves the wheel. With those in hand, a compatibility question takes one message instead of three.
Most of this checklist needs a multimeter and clean hands. If a corroded plug turns out to be the fault, replacing that connector is a repair worth doing properly rather than twisting wires together — our workshop tools cover the crimping and sealing side of it.