It Won't Turn On, or Won't Move: Find the Fault in Ten Minutes
The most common problem in RC, and the one where people do the most damage by changing parts at random. Work the chain in order — power, radio link, ESC, motor, drivetrain — and stop at the first thing that fails.
Updated Jul 22, 2026 · RC Crash Crew
Your RC does nothing. Or it makes noise and does not move. Or it worked yesterday and today it does not.
This is the most common problem in the hobby and the one where people do the most damage, because the instinct is to start changing parts. Almost every one of these faults is found in ten minutes by working through the chain in order and changing one thing at a time.
⚠️ Before you start
- Wheels off the ground, on a stand or a box. A car that suddenly comes to life at full throttle on the bench is how people get hurt and how bodies get destroyed.
- Disconnect the battery before touching wiring, and read the safety rule in the soldering guide if you are cutting anything.
- Transmitter on FIRST, model on second. Model off FIRST, transmitter off last. Get this backwards while diagnosing and you will chase a fault that is not there.
The chain, in order
Power → radio link → ESC → motor → drivetrain. A fault can only be at the first point where the chain stops. Work forwards and stop at the first thing that fails.
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Stage 1 — Nothing at all. No lights, no beeps, no servo twitch.
The model is not getting power. Almost always one of five things.
1. The battery is flat, or flatter than it looks.
Measure it. A lithium pack that reads low per cell is not "a bit low", it is empty — and if a cell has dropped very low it may not be safe to charge at all. See the charger guide for the numbers, and the LiPo safety guide before reviving anything.
2. The connector is not fully seated. Push it home properly. Bullet connectors in particular can look connected while sitting a couple of millimeters out.
3. The switch. Obvious, and it is genuinely the answer often enough to check first. Some models have a switch on the ESC, some on the receiver, some a mechanical switch on the body.
4. A broken wire at a connector. This is the sneaky one. Wire fatigues where it enters a plug, and the break is *inside the insulation* where you cannot see it. Flex each lead gently near the connector while watching for the ESC light to flicker. If it flickers, you found it.
5. Corrosion. Green or white powder on the contacts, usually after a wet run. Clean it or replace the connector.
⚠️ A pack that reads fine at rest can still be dead under load. If everything checks out but the model dies the instant the motor tries to turn, suspect the pack — internal resistance rises as packs age.
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Stage 2 — ESC has power, but nothing responds.
Lights are on, maybe a beep, but the steering does not move and the throttle does nothing.
The radio link is the suspect.
- Is the transmitter on, and are its batteries good?
- Is it bound to this model? And is the right model memory selected? See the binding guide.
- Is the failsafe holding it? If the receiver thinks it has lost signal, it will sit at the failsafe position and ignore you. The failsafe guide covers this.
- Receiver LED — solid usually means linked, flashing usually means searching. Your manual is the authority.
- Servo plugs in the right channels, right way round. Steering and throttle swapped is a surprisingly common "nothing works" that is really "everything works, on the wrong stick".
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Stage 3 — Steering works, motor does not.
The radio link is fine — this narrows things a lot.
- ESC arming. Most ESCs will not arm unless the throttle is at neutral when powered on. Trim drifted off center is enough to stop it. Set trim to zero, power cycle.
- Throttle calibration. If the ESC has never been taught your transmitter's endpoints, or you changed radios, it needs re-calibrating. The ESC programming guide covers this.
- LVC — low voltage cutoff. The ESC has decided the pack is too low and cut the motor to protect it. Steering still works because the receiver still has power. This is the ESC doing its job, not a fault. Charge the pack.
- Thermal shutdown. If it was working and stopped after a hard run, feel the ESC and motor. Too hot to hold means it protected itself. Let it cool, then find out *why* — usually gearing or mesh. See why RC electronics die.
- Motor wires. Two for brushed, three for brushless. Check each connection at both ends.
- Turn the motor by hand (disconnected). Smooth? A seized or grinding motor is the answer. Gritty means bearings.
- Sensor cable, on a sensored brushless system. A damaged sensor lead gives stuttering, cogging, or nothing.
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Stage 4 — Motor spins, wheels do not.
You can hear it. Nothing moves. The drivetrain is broken somewhere, and this is usually the cheapest fault on the page.
- Stripped spur gear. The classic. Take the gear cover off and look — you will usually see it instantly. Then read the gear mesh guide before fitting a new one, because a bad mesh is what killed it.
- Slipper clutch too loose. If it slips under any load, the motor spins and the car crawls or does nothing. Tighten a fraction at a time.
- Stripped or empty differential. Lift one end: hold one wheel and turn the other. No resistance at all, or one wheel spinning freely with nothing happening at the other, points here. See the differentials guide.
- Driveshaft out or a stripped dogbone/pin. Look underneath while someone turns the wheel.
- Something jammed. Grass, string, a stone, or wire wound around a driveshaft. Extremely common after a run in long grass.
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Stage 5 — It works, then cuts out.
Intermittent faults are the worst to find because you can only test them when they happen.
| Pattern | Usual cause |
|---|---|
| Cuts out under hard throttle, comes back | Pack sagging under load, or LVC |
| Cuts out over bumps and jumps | Connector working loose, or a wire breaking as it flexes |
| Cuts out at distance, fine up close | Radio range — antenna routing or a damaged antenna |
| Cuts out after a few minutes, every time | Heat — ESC or motor thermal protection |
| Random, no pattern, servos twitch | Receiver browning out — BEC cannot supply the current |
| Only since a crash | A wire pulled or a connector cracked at the impact point |
Brownout deserves its own note: if the servo is drawing more current than the ESC's BEC can supply, the receiver loses voltage for a moment and reboots. The symptoms look like radio interference. See the servo guide — a bigger servo makes this worse, not better.
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The method that actually finds it
1. Change one thing, then re-test. Two changes at once and you learn nothing, even if it starts working.
2. Halve the problem. Do not test parts in the order they are easiest to reach — test in the middle of the chain and see which half the fault is in. "Does the steering work?" splits the whole problem in two in one second.
3. Swap in something known-good. A spare pack, a spare servo, a receiver from another model. A known-good part turns a guess into a fact.
4. Write down what you tried. Ten minutes in, you will not remember whether you already re-seated that connector.
5. Two tools do most of the work. A multimeter for continuity and voltage, and a battery checker for cell voltages. Neither is expensive and both replace guessing with knowing. See the first toolkit guide.
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When you genuinely cannot find it
Post it. Say what it does, what it does not do, and every single thing you have already tried — that last part is what makes people able to help instead of repeating your first ten minutes back at you.
The forums and the Repair Desk are both for this, and a fault written up properly becomes the page that helps the next person with the same symptom.