THE FIRST STEPS & ELECTRICAL
This is the most crucial, inexpensive task a technician should perform with a customer first, before touching any diagnostic tools.
What is patient interviewing/communication? (Also accepts visual inspection)
Low head pressure, high suction pressure, and an abnormal knocking or rattling sound are symptoms of this non-electrical compressor failure.
What is mechanical failure? (Accepts worn pistons/rings, broken crankshaft, or blown valve plates)
This relay type uses the start winding's back electromotive force (EMF) to disengage the start winding and is generally used on larger single-phase compressors.
What is a potential relay? (Also accepts voltage relay)
Low suction pressure and low superheat can often be attributed to this kind of issue at the evaporator, where there is not enough warm air to keep it above freezing.
What is low airflow? (Also accepts dirty evaporator coil/faulty fan)
To verify non-condensables like air are in a shut-off system, a technician lets the system reach room temperature and compares the pressure to the prediction of this tool.
What is a Pressure-Temperature (PT) chart?
The two main areas into which electrical troubleshooting is divided.
What are diagnosing controls (switches, relays, contactors) and diagnosing loads (coils, fan motors, compressors)?
This testing tool isolates the compressor from its external relays and capacitors, applying power directly to the run and start windings.
What is a compressor analyzer?
These solid-state starting devices, which have normally open contacts and act as resistors, use high startup current to disconnect the start winding.
What are current relays?
High discharge pressure, high amperage draw, and poor cooling results when this coil is dirty or its fan is faulty.
: What is the condenser?
Oil stains are often the first sign of this system failure, because oil typically leaks out with the refrigerant.
What is a refrigerant leak?
The practice of placing one voltmeter lead on a known good ground/L2 and moving the other point-by-point along L1 to find an open in a series circuit.
What is hopscotching?
The manufacturer provides this current rating specifically for the compressor under normal, full-load operation.
What is FLA (Full Load Amps)?
The component type that increases in resistance when heated, requiring a cool-down before checking with an ohmmeter.
What is a PTC (Positive Temperature Coefficient) starting relay?
This measurement is the temperature difference between the actual suction line temperature and the saturation temperature at the same pressure.
What is superheat?
In noisy environments or to find leaks of air or nitrogen, this handheld detector does not look for specific chemical molecules but listens for the high-frequency hiss of escaping gas.
What is an ultrasonic leak detector?
For safety, hopscotching is done while the circuit is in this state.
What is energized (power on)?
A critical threshold temperature (Fahrenheit or Celsius) above which compressor oil breaks down, losing its lubricating ability and inviting mechanical seizure.
What is 250f (or 121C)?
In the upright position, a current relay’s normally open contacts should read open, but they will close with zero resistance when flipped this way due to gravity.
What is upside down?
This is the expected superheat range, in Fahrenheit, that a thermostatic expansion valve (TXV) is designed to maintain at the evaporator outlet.
What is 8 to 12 degrees?
This detector, which uses an ultraviolet light to make leak points glow, is especially useful for slow or intermittent leaks.
What are fluorescent refrigerant dyes?
Checking for this failure type is done by testing the resistance between each of a capacitor's terminals and its metal case with an ohmmeter.
What is a short to ground?
Technicians must establish the cause of an original compressor’s demise before dropping in a new one to avoid this costly occurrence.
What is a repeat/premature failure?
This is the most common visual indicator that a run capacitor is bad, indicating it has failed internally and should be replaced.
What is a visible bulge on the top or a cracked case?
A restricted filter drier or inlet screen, gas charge condensation in the remote bulb, or low refrigerant charge will cause this superheat condition.
What is high superheat?
The specialized piece of equipment used on small-capacity systems, like ice machines, to connect for test readings with minimal hose volume so that several ounces of refrigerant are not lost when disconnected.
What is a short refrigerant gauge?