Service & Repair
Part of the HVAC Technician training program
Overview
Master the diagnostic and repair skills that separate technicians from technicians. This capstone module covers advanced troubleshooting methodologies, electrical diagnosis, preventive maintenance programs, and the business skills essential for a successful HVAC career.
Sub-topics
Advanced Electrical Diagnostics
Use multimeters and megohmmeters to diagnose motor windings, capacitor health, contactor wear, and control circuit faults. Study variable speed drive troubleshooting, zone control system diagnostics, and low-voltage communication bus errors in modern equipment.
Lessons
Motor Windings Testing
Use megohmmeter to test motor insulation resistance. Understand phase-to-phase and phase-to-ground readings. Learn about insulation degradation indicators.
Capacitor Health Check
Test start and run capacitors with capacitance meter. Understand microfarad values and ESR measurements. Learn signs of capacitor failure.
Contactor Inspection
Visually inspect contactor contacts for pitting and burning. Test coil resistance and contact alignment. Understand proper operating sequence.
Control Circuit Faults
Trace 24V control circuits using wiring diagrams. Test relays, timers, and safety switches. Understand series and parallel control component operation.
VFD Troubleshooting
Read VFD fault codes and status indicators. Understand DC bus voltage, current limits, and motor parameter settings.
Practical Exercises
- Test motor windings with megohmmeter (minimum 500 megohms)
- Measure start capacitor microfarad value and compare to nameplate
- Inspect contactor for pitting and test coil resistance
- Trace 24V circuit to find open safety switch
- Reset VFD fault and verify proper operation
Key Formulas
Motor FLA = 1.15 × HP × 1000 / (V × PF)Capacitor Microfarads = 1000 × W / (V² × 2π × f)Required Tools
System Troubleshooting Methodology
Develop a systematic approach to HVAC diagnosis using process-of-elimination testing, symptom-based flowcharts, and data-driven decision making. Practice diagnosing 20+ common system failure modes across residential and light commercial equipment.
Lessons
Symptom Analysis
List all observed symptoms and prioritize by importance. Understand that one fault can cause multiple symptoms.
Process of Elimination
Test most likely causes first. Use “divide and conquer” approach to narrow down fault location.
Common Failure Modes
Study 20+ failure modes including low charge, restricted airflow, electrical faults, and control problems. Understand typical symptoms for each.
Data-Driven Decision Making
Record all measurements and compare to normal values. Use superheat, subcooling, and temperature split for system assessment.
Documentation
Record all findings and corrective actions. This builds diagnostic skill and provides service history.
Practical Exercises
- Diagnose system with no cooling using systematic approach
- Identify airflow problem from temperature split measurements
- Find cause of high energy consumption from electrical data
- Trace intermittent control fault using process of elimination
- Document complete diagnosis with measurements and findings
Safety Checklist
- Always verify power is off before electrical testing
- Use lockout/tagout for motor work
- Wear safety glasses during electrical testing
- Test voltage with meter before handling wires
- Check for refrigerant leaks before system opening
Preventive Maintenance Programs
Design and implement preventive maintenance schedules for different system types. Learn coil cleaning techniques, filter selection, lubrication protocols, belt adjustment, and performance trending to identify equipment degradation before failure occurs.
Lessons
Maintenance Scheduling
Create schedules based on runtime hours, calendar time, or operating seasons. Understand different requirements for residential vs. commercial systems.
Coil Cleaning Techniques
Use foaming coils cleaner and low-pressure rinse. Understand importance of clean coils for efficiency and airflow.
Filter Replacement
Select proper filter MERV rating. Understand pressure drop indicators and replacement intervals.
Belt Adjustment
Set proper belt tension (deflection method). Understand correct pulley alignment and belt wear indicators.
Performance Trending
Record superheat, subcooling, and electrical data over time. Identify gradual degradation before failure.
Practical Exercises
- Clean condenser coil with foaming cleaner
- Replace air filter with correct MERV rating
- Adjust belt tension on blower motor
- Record baseline measurements for future comparison
- Create maintenance schedule for commercial system
Safety Checklist
- Always run system before performance measurements
- Wear gloves when handling chemical cleaners
- Use proper ladder safety for high coil access
- Check electrical connections before running system
- Record all measurements in maintenance log
Indoor Air Quality & Ventilation
Assess indoor air quality parameters including humidity control, filtration efficiency, UV-C germicidal treatment, and mechanical ventilation strategies. Practice installing air cleaners, humidifiers, ERV/HRV systems, and ductless mini-split zoning for commercial applications.
Lessons
Humidity Control
Measure relative humidity and understand dew point. Learn about dehumidification methods and moisture sources.
Air Filtration
Understand MERV ratings and particle size removal. Learn about HEPA and UVGI technologies.
UV-C Germicidal Treatment
Install UV-C lamps in airstream for microbial control. Understand lamp positioning and maintenance requirements.
ERV/HRV Systems
Study energy and humidity recovery ventilators. Understand heat pipe and rotary wheel technologies.
Mini-Split Zoning
Install and balance multiple indoor units on single outdoor unit. Understand refrigerant charge for each zone.
Practical Exercises
- Measure humidity and calculate dew point
- Replace UV-C lamp in air handler
- Install ERV and connect to existing ductwork
- Balance airflow on multi-zone mini-split
- Select proper filter for given air quality requirement
Safety Checklist
- Verify electrical power is off before installing UV-C lamps
- Check UV-C exposure during installation
- Verify ERV bypass damper operation
- Test mini-split zones for proper refrigerant charge
- Document all IAQ improvements made
Required Tools
Learning Objectives
- Diagnose and repair complex electrical faults in HVAC control systems using proper test procedures
- Apply systematic troubleshooting methodology to identify root causes of 20+ common system failures
- Design and implement a preventive maintenance program for residential and light commercial systems
- Evaluate indoor air quality and recommend appropriate remediation solutions
- Perform combustion analysis and adjust gas-fired equipment for optimal efficiency and safety
- Complete a comprehensive service call including diagnosis, repair, and customer documentation