// bench playbook · BP-001 · HVAC
No-cool callback after a capacitor swap that would not hold.
The dual-run cap reads in spec at the truck, then droops under pull-down. Three truck rolls in ten days. One bench move that closes the loop.
A no-cool call opens on a 4-year-old 3-ton. The tech pulls the dual-run capacitor, sees it bulged, reads 4.6 µF on a 35 µF spec, swaps it, sends the unit. The same call comes back nine days later: same complaint, same amp trace, a different cap that now bulges at the lens. Both caps came out of the same regional distributor lot. The third truck roll finds a 21-percent amp-draw over nameplate FLA and a delta-T that collapses inside 90 seconds of pull-down — neither a cap problem on its own.
The cap is the symptom. Something on the line is over-stressing it. The board code is not the failure; the board code is the symptom of a misread on the prior visit.
Truck rolls
3
Capacitor stock
$72
Warranty write-off
~$280
bench move
Before authorizing the third visit, the bench reviewer asks for two numbers under steady-state load: compressor amp draw vs. nameplate FLA, and return-side delta-T at the 90-second mark.
- 01Meter the MFD µF cold out of the truck, not at the unit — a hot capacitor can read back in spec and fail on the next pull-down.
- 02Recompute amp draw under load; cap failure under-runs amps, it does not over-run them.
- 03Rebuild delta-T from return to supply at the 90-second mark of pull-down; collapse inside the first 90 s names refrigerant overcharge as the live suspect.
- 04Recover to nameplate superheat and re-verify delta-T held under design load before clearing the call.
// Send the setup brief
Bring us the ticket that already cost you a callback.
The intake is four fields; an owner reads every one within one business day. We will tell you straight if your line is not a fit for the $997 setup before you spend money.
// 4 fields · owner reads every one · reply within one business day
Related playbooks
// 2 more
- BP-002 · appliancebench playbook
E15 on a dishwasher — the control board reorder that did not hold.
Three warranty callbacks in three weeks. The board keeps coming back. The float switch never got metered under a dry-cycle drain test before the reorder.
- BP-003 · plumbingbench playbook
Tankless E11 within 48 hours of a flow-sensor clean — the bench playbook.
A 12-year-old Rinnai keeps throwing E11 inside two days of a flow-sensor cleaning. The sensor is the right swap. The read is in the wrong place.
// Signoff
— secondshift-3. The bench is the difference between a ranked guess and a verifiable verdict on a $4,000 part swap. Each playbook in this column came out of one.