HVAC Troubleshooting Mastery
Certification Exam (2026 Edition)||
questions and answers with
rationales/graded A+/2026
update/100% correct /instant
download
Exam Code: HVAC-TM-2026
Total Questions: 85
Time Allowed: 3 hours
Passing Score: 75%
Topics: Electrical Troubleshooting, Refrigeration Cycle, Controls & Sensors,
Airflow & Duct Diagnostics, Heat Pumps, Gas Furnaces, Commercial Systems,
Smart HVAC & IoT Diagnostics.
Section 1: Electrical Troubleshooting (15 Questions)
1. A technician measures 24V between R and C at the thermostat but 0V between
R and W when calling for heat. The furnace does not start. What is the most likely
fault?
a) Bad transformer
b) Open limit switch
c) Faulty thermostat or wiring between R and W
d) Shorted gas valve
Rationale: 24V at R-C proves power to thermostat. 0V at R-W with heat call
indicates the thermostat switch or wiring from W back to furnace is open.
, 2. When testing a potential relay on a single-phase compressor, the technician finds
continuity between terminals 1 and 2, and no continuity between 2 and 5. The relay
is:
a) Normal for a loaded relay
b) Defective – contacts welded
c) Normal for unloaded (coil de-energized)
d) Defective – coil open
Rationale: Terminals 1-2 are the relay coil (low resistance). Terminals 2-5 are
normally closed contacts. Open contacts between 2-5 when unpowered indicates
welded or stuck open – incorrect operation.
3. A dual-run capacitor is rated 40+5 µF ±6%. Measured values: 38 µF (HERM)
and 4.2 µF (FAN). Action?
a) Replace only if compressor fails
b) Acceptable – within tolerance
c) Replace immediately – too low
d) Add a hard start kit
Rationale: 38 µF is 95% of 40 – within 6% (±2.4 µF). Fan at 4.2 µF is 84% –
borderline but acceptable. No replacement needed.
4. Short cycling of a refrigeration compressor (3 min off time) is often caused by:
a) Low refrigerant
b) Loose thermostat wire
c) Anti-short cycle timer set to 1 min
d) High discharge pressure
Rationale: Short cycling with ~3 min off suggests anti-short cycle timer working
but possibly intermittent control signal or loose wire making/breaking call.
5. A PSC blower motor runs at half speed continuously. Voltage at motor terminals
is 120V. The most likely cause:
a) Open start winding
b) Failed run capacitor
c) Shorted centrifugal switch
d) Low voltage from transformer
Rationale: PSC motors rely on run capacitor for phase shift. Failed cap causes low
torque, reduced speed, overheating.
Certification Exam (2026 Edition)||
questions and answers with
rationales/graded A+/2026
update/100% correct /instant
download
Exam Code: HVAC-TM-2026
Total Questions: 85
Time Allowed: 3 hours
Passing Score: 75%
Topics: Electrical Troubleshooting, Refrigeration Cycle, Controls & Sensors,
Airflow & Duct Diagnostics, Heat Pumps, Gas Furnaces, Commercial Systems,
Smart HVAC & IoT Diagnostics.
Section 1: Electrical Troubleshooting (15 Questions)
1. A technician measures 24V between R and C at the thermostat but 0V between
R and W when calling for heat. The furnace does not start. What is the most likely
fault?
a) Bad transformer
b) Open limit switch
c) Faulty thermostat or wiring between R and W
d) Shorted gas valve
Rationale: 24V at R-C proves power to thermostat. 0V at R-W with heat call
indicates the thermostat switch or wiring from W back to furnace is open.
, 2. When testing a potential relay on a single-phase compressor, the technician finds
continuity between terminals 1 and 2, and no continuity between 2 and 5. The relay
is:
a) Normal for a loaded relay
b) Defective – contacts welded
c) Normal for unloaded (coil de-energized)
d) Defective – coil open
Rationale: Terminals 1-2 are the relay coil (low resistance). Terminals 2-5 are
normally closed contacts. Open contacts between 2-5 when unpowered indicates
welded or stuck open – incorrect operation.
3. A dual-run capacitor is rated 40+5 µF ±6%. Measured values: 38 µF (HERM)
and 4.2 µF (FAN). Action?
a) Replace only if compressor fails
b) Acceptable – within tolerance
c) Replace immediately – too low
d) Add a hard start kit
Rationale: 38 µF is 95% of 40 – within 6% (±2.4 µF). Fan at 4.2 µF is 84% –
borderline but acceptable. No replacement needed.
4. Short cycling of a refrigeration compressor (3 min off time) is often caused by:
a) Low refrigerant
b) Loose thermostat wire
c) Anti-short cycle timer set to 1 min
d) High discharge pressure
Rationale: Short cycling with ~3 min off suggests anti-short cycle timer working
but possibly intermittent control signal or loose wire making/breaking call.
5. A PSC blower motor runs at half speed continuously. Voltage at motor terminals
is 120V. The most likely cause:
a) Open start winding
b) Failed run capacitor
c) Shorted centrifugal switch
d) Low voltage from transformer
Rationale: PSC motors rely on run capacitor for phase shift. Failed cap causes low
torque, reduced speed, overheating.
