Motor Problems
Props off for every test on this page. All four symptoms are diagnosed at the bench, and three of them involve motors doing things you don't expect.
One motor twitches or stutters at idle
The three-phase joints are the classic: a cold solder joint on one phase makes a motor that mostly works and intermittently stutters — the flip-of-death joint Module 10 warns about. Tug-test and reflow before buying anything.
A motor won't spin and beeps
A brushless motor that beeps but won't turn is usually missing one phase — the ESC is energizing two of three wires. Same tree as above, but check the obvious first: a phase wire pulled from its pad in a crash. Three good joints or it doesn't fly (ESC).
Motors come down hot
The middle branch is Module 9's whole tuning loop: raising cutoffs and gains buys crispness until motor temperature says stop. The left branch is Propellers' heating result — the most common way to kill a fresh build.
Desyncs — a motor drops out under punch
| Check, in order | Why | Link |
|---|---|---|
| Capacitor fitted and healthy? | Voltage spikes corrupt ESC commutation exactly at full load | Module 6 |
| ESC current rating vs the build's ~120 A punch-out? | Undersized ESCs desync before they smoke | ESC, cheat sheet |
| Phase joints solid? | A marginal joint fails under current, not at idle | Module 10 |
| ESC firmware current? | Older BLHeli_S builds desync where Bluejay/AM32 don't | Flashing firmware |
| Pack healthy? | A worn pack's sag can dip below the ESC's brownout under punch | Battery |
Re-run the props-off motor test (order, direction, smooth spin-up) and listen to the first hover — the post-crash test-flight rule applies to bench work too.