Repair guides
Pick a type, an appliance or a brand. Every guide lists the tools, the safety call-outs, the steps and the reading you should expect.
Diagnostic · 374
Symptom → most likely cause, step by step
Component tests · 69
How to test a specific part, with expected readings
Installation · 33
Install, replace and hook up appliances correctly
Fundamentals · 24
Core skills every appliance tech uses
Appliance
Brand-specific guides
4 guides · Air Conditioners
Component tests · 4
Component test · Air Conditioner24 V control transformer (HVAC)
The control transformer steps line voltage down to about 24 V AC for the thermostat, board and contactor coil. Measure primary and secondary under power; a blown low-voltage fuse means a short in the 24 V wiring, not a bad transformer.
Component test · Air ConditionerContactor (HVAC): coil, contacts and voltage drop
The contactor closes line voltage to the compressor and fan when it gets 24 V on its coil. Check coil voltage, coil resistance, contact condition and voltage drop across closed contacts.
Component test · Air ConditionerDual run capacitor (HVAC condenser): testing both sections
A dual capacitor has C (common), HERM (compressor) and FAN terminals with two µF ratings in one can. Test C-HERM and C-FAN separately against the label; one section can fail while the other is fine.
Component test · Air ConditionerMini-split outdoor inverter board: what is safe to check
Mini-split outdoor boards rectify line voltage to a high DC bus and drive the compressor and fan. Field checks are input power, communication, error codes and compressor winding balance. Board DC bus voltage is dangerous after shutdown.