RC car won't run? Work the chain in order from battery to motor, read the ESC beeps and blinks, and rule out the five embarrassing causes first.
Your car was fine last weekend. Now you flip the switch and get nothing. No wheels, no steering, maybe a sad little beep or a blinking light you've never noticed before. I've been there more times than I'll admit, and about eight times out of ten it's something dumb that takes thirty seconds to fix once you know where to look.
The trick is working the chain in order instead of tearing the car apart. Power comes from the battery, runs through the connectors and the switch into the ESC, which feeds the receiver, which talks to the servo and the motor. Start at the front of that chain and move back. Don't skip steps because you're pretty sure it's the motor, because you're usually wrong about that.
Before you get out a screwdriver, rule out the stuff that makes you feel silly later. I check all five of these every time now.
Storage-charged pack. Any LiPo you leave sitting drops to a storage voltage around 3.8V per cell, which isn't enough to run hard, and if it self-discharged further it'll trip the ESC's low-voltage cutoff the second you punch the throttle. Put it on the charger. A dead car is a dead battery far more often than anything else.
Throttle trim. Somebody bumped the trim knob on your transmitter, or it drifted. If the car creeps or does nothing at neutral, center your throttle trim and re-check.
Failsafe fired. If the receiver lost signal even once, a lot of setups latch into failsafe and sit there refusing throttle until you power-cycle. Transmitter on first, then the car, every time.
Dead transmitter batteries. A weak TX throws all kinds of ghost problems: random cutouts, no bind, twitchy servos. Fresh cells. I keep a spare four-pack in the pit bag.
A loose switch. On-off switches are the flimsiest part on the whole car. The little slider cracks, a wire fatigues right at the solder joint, and the switch stops doing anything. Wiggle it, and if wiggling changes anything, that's your answer.
Once the obvious stuff is clear, the ESC is your best witness. Hobbywing, Castle, Spektrum and Tekno units all use a status LED and startup beeps to tell you what they think is wrong. Exact patterns differ by brand, so pull the manual for your specific ESC rather than guessing from a forum thread about a different one, but the general classes hold:
The startup beep sequence matters too. Most brushless ESCs play a little tune when they detect the battery, then a second tone when they see a good neutral throttle signal. Battery tones but no ready tone means the ESC has power but isn't getting a clean signal from the receiver. Nothing at all is a power problem upstream.
Almost every no-run falls into one of three buckets, and telling them apart saves you an hour.
Power problem. Nothing lights up, nothing beeps, the servo is dead too. The car is electrically asleep. Battery, connectors, switch.
Binding problem. The ESC lights up and the servo works, but you get no throttle, or the car ran and then quit mid-session. The receiver and transmitter aren't talking. Re-bind them, check the TX battery, and make sure you didn't power up in the wrong order.
Mechanical problem. The motor tries. You hear it strain, it stutters, it gets hot, but the wheels don't turn or they turn rough. Something's jammed: a stripped spur gear, a rock wedged in the drivetrain, a locked-up diff, a slipping slipper clutch. Pull the battery and spin the wheels by hand, and if they don't turn freely it isn't electronics at all.
That hand-spin test is the fastest way to split mechanical from electrical, so do it early.
If the ESC is lit and you've re-bound, plug the servo directly into the receiver channel it belongs on and try steering. Steering working but throttle dead is a strong sign the receiver and transmitter are fine and the problem is downstream in the ESC or motor. Steering dead too points back at the receiver or its power.
Motors fail differently depending on type. A brushed motor with worn brushes will run weak, cut out under load, or spin one direction only. A brushless motor rarely dies quietly, so usually you smell it or one of the three phase wires cooked. If the motor gets hot fast and cuts out while the ESC throws an over-temp blink, the motor or the gearing is dragging.
Swap in a known-good battery and a known-good receiver first so those are isolated. Then, if the ESC arms and beeps normally but the motor won't spin or even twitch, and the motor turns fine by hand, suspect the ESC's output stage. If the ESC won't arm at all, or resets the instant you touch throttle, that's often a shorted or failing motor dragging the ESC into protection.
The quick check is to unplug the motor from the ESC and power up. If the ESC now arms and beeps clean with no motor attached, the ESC is probably fine and the motor is your suspect. If it still faults with nothing connected, the ESC is the problem.
You don't need a fancy one. A $15 multimeter from the hardware store settles arguments in seconds. Set it to DC volts and check your pack at the balance plug, where a healthy 2S LiPo reads around 7.4V nominal and up near 8.4V full, and a 3S reads around 11.1V nominal. Anything sagging well below nominal is your no-run right there.
You can also buzz out continuity through the switch and the connectors. Probe both sides, and if a switch shows no continuity when it's on, you found the dead link. I check every crimped and soldered joint this way whenever a car's had a few hard crashes, same as I do during post-run maintenance.
Work the chain, read the lights, spin the wheels by hand, and most no-runs give themselves up in five minutes. The rest are usually a fried ESC or a tired motor, and at that point you know exactly what to buy instead of guessing.
If it's cheaper to replace than repair, you can usually find a solid used ESC or motor from someone parting out a roller in the marketplace listings, or catch a new one cheap on the deals page. And if the power-up order and re-binding stuff is still fuzzy, how transmitters and receivers talk to each other covers failsafe and binding in more depth.