CAT Troubleshooting & Diagnostics 2 — Questions and Answers
Question 1: A smoke detector repeatedly triggers false alarms only during early morning hours. What is the most likely cause?
- Faulty wiring in the detector loop
- Condensation or temperature fluctuations at dawn (Correct answer)
- Low battery condition
- Improper detector placement near HVAC return
Correct answer: Condensation or temperature fluctuations at dawn
Early morning false alarms from smoke detectors are most often caused by condensation or temperature differentials that occur at dawn.
Question 2: When a zone shows a 'short circuit' fault on the control panel, what resistance measurement would you expect when testing the zone wiring?
- Open circuit (infinite resistance)
- Near zero ohms (Correct answer)
- End-of-line resistor value (e.g., 5.6kΩ)
- Twice the EOL resistor value
Correct answer: Near zero ohms
A short circuit fault indicates the zone wires are touching, resulting in near-zero ohm resistance.
Question 3: A PIR motion detector triggers when no motion is present whenever a heating vent activates nearby. The best corrective action is to:
- Replace the PIR with a newer model
- Aim the detector away from the vent or install a heat-shielded model (Correct answer)
- Increase the detector's sensitivity setting
- Move the HVAC vent to another location
Correct answer: Aim the detector away from the vent or install a heat-shielded model
PIR detectors respond to infrared heat changes, so redirecting the detector away from the vent or using a heat-shielded unit eliminates false triggers from HVAC airflow.
Question 4: After restoring AC power to a security panel following an outage, the panel shows a 'battery trouble' fault. What should you check first?
- Replace the backup battery immediately
- Verify the battery is connected and measure its voltage (Correct answer)
- Reset the panel to clear the fault
- Check the transformer output voltage
Correct answer: Verify the battery is connected and measure its voltage
Before replacing the battery, verify it is properly connected and measure its voltage to determine if it is genuinely failed or just discharged.
Question 5: A keypad displays 'Communication Failure' but all zones are normal. Which component should be tested first?
- All motion detectors on the system
- The phone line, broadband connection, or cellular communicator (Correct answer)
- The backup battery voltage
- Zone wiring continuity
Correct answer: The phone line, broadband connection, or cellular communicator
A communication failure fault points specifically to the reporting path (phone line, IP, or cellular), which should be tested first.
Question 6: You measure 13.8V DC at a panel's battery terminals while AC is present, but only 10V after disconnecting AC. This indicates:
- The transformer is overloaded
- The battery is sulfated or near end-of-life (Correct answer)
- The EOL resistors are incorrect
- The panel's power supply is faulty
Correct answer: The battery is sulfated or near end-of-life
A battery that drops sharply under load when AC is removed is sulfated or degraded and cannot hold adequate charge.
Question 7: A siren activates briefly during a thunderstorm even though no zone was triggered. What is the most probable cause?
- A zone wire picked up induced voltage from lightning (Correct answer)
- The panel firmware needs updating
- The siren is wired in reverse polarity
- The control panel needs a factory reset
Correct answer: A zone wire picked up induced voltage from lightning
Lightning-induced voltage spikes can couple onto unshielded zone wires and cause momentary false triggers.
CAT Troubleshooting & Diagnostics 2
A smoke detector repeatedly triggers false alarms only during early morning hours.
What is the most likely cause?