Furnace Won't Turn On? Portland Troubleshooting Guide
10 common reasons your furnace won't start and step-by-step solutions. Portland natural gas furnace startup diagnostics.
Owner & Lead HVAC Technician
🔍 Quick Furnace Startup Diagnosis
Does It Make Any Sound?
- No sound at all: Power issue (breaker, switch)
- Clicking sounds: Thermostat or gas valve
- Humming/buzzing: Control board or transformer
- Whooshing gas sound: Gas valve open but no ignition
Emergency Indicators:
- • Gas smell (evacuate, call 911)
- • Yellow flames (carbon monoxide risk)
- • Excessive soot (venting problem)
- • Pilot light won't stay lit
- • Furnace is 15+ years old
Portland Tip: October "first cold snap" often reveals startup issues after months of furnace inactivity.
Understanding Furnace Startup Problems in Portland
A furnace that won't turn on is one of the most urgent heating emergencies Portland homeowners face, especially during our variable winter weather. After 17 years serving the Portland metro area, I've diagnosed thousands of furnace startup failures, from simple power issues to complex control board failures. Portland's climate creates unique challenges: our mild winters mean furnaces sit dormant for months, then face sudden demands during rare cold snaps, often revealing hidden problems.
This guide covers the 10 most common reasons Portland furnaces won't start, with clear steps for what you can safely troubleshoot yourself and when to call our emergency technicians. We'll cover both standing pilot systems (common in older Portland homes) and modern electronic ignition systems. Remember: some startup problems are simple fixes, while others indicate safety issues requiring immediate professional attention.
Start with the basics (power, thermostat, gas supply) before moving to more complex diagnostics. If you're ever unsure or smell gas, stop immediately and call for professional help.
10 Common Causes of Furnace Won't Turn On (In Order of Likelihood)
1. Power Supply Issues (Most Common - 40%)
Symptoms
- • Furnace completely silent
- • No response to thermostat
- • Digital display blank
- • After power outage
Common Causes
Tripped circuit breaker, emergency shutoff switch flipped, or power outage. Portland's winter storms can cause power fluctuations that trip furnace breakers.
DIY Solution
- Check main electrical panel for tripped breaker
- Look for emergency shutoff switch (usually red) near furnace
- Ensure furnace power switch is ON
- Check if other circuits work (confirms breaker issue)
- Reset breaker if safe to do so
Safety Note
Never reset breaker if you smell burning or see damage. Call electrician first.
Portland Context: Winter storms cause frequent power fluctuations. Keep emergency shutoff location marked.
2. Thermostat Issues
Symptoms
- • Clicking from thermostat but no furnace response
- • Display shows wrong temperature
- • Furnace runs when it shouldn't
- • Inconsistent operation
Common Issues
Dead batteries, incorrect settings, poor location, or wiring problems. Portland homes often have thermostats in drafty hallways or near windows.
DIY Troubleshooting
- Replace batteries (AA or AAA)
- Check if set to "HEAT" mode
- Verify temperature setting above room temp
- Check for "HOLD" or vacation mode
- Test by increasing temperature 5 degrees
Professional Service
If thermostat faulty, replacement needed. Cost: $150-350.
Portland Tip: Older homes may have incompatible thermostats. Check voltage compatibility when replacing.
3. Pilot Light Out (Standing Pilot Systems)
Symptoms
- • Furnace clicks but burners don't ignite
- • No visible pilot flame
- • Gas smell when trying to start
- • Only fan runs
Standing Pilot Systems
Common in Portland homes built before 1990. These maintain a small constant flame that ignites burners when heat is called for.
DIY Relighting
- Turn thermostat to lowest setting
- Wait 5 minutes for gas to clear
- Find pilot light access door
- Press and hold pilot button
- Light pilot with match or lighter
- Hold button 30 seconds after lighting
⚠️ Safety Critical
If pilot won't stay lit after 3 attempts, call professional. Could indicate thermocouple failure.
Cost: Thermocouple replacement $100-200 if needed.
Additional Startup Problems (4-10)
The remaining 7 causes with key details:
4. Gas Valve Closed
Manual gas valve off. Turn on, check for leaks. Call NW Natural if needed.
5. Flame Sensor Dirty
Prevents ignition safety. Clean or replace: $100-250.
6. Pressure Switch Issues
Venting problem. Replace switch: $150-300.
7. Blown Fuse
Internal fuse blown. Replace: $50-150.
8. Limit Switch Tripped
Overheat protection. Reset or replace: $150-300.
9. Electronic Ignition Failure
Hot surface igniter bad. Replace: $150-400.
10. Control Board Failure
Furnace brain failure. Replace: $300-800.
When Furnace Startup Problems Require Professional Service
🚨 Emergency - Call Immediately:
- Smell gas or rotten eggs
- Yellow or flickering flames
- Loud banging or explosions
- Smoke or burning smells
- Furnace repeatedly won't start
🔧 Schedule Service Soon:
- Furnace is 10+ years old
- Annual maintenance overdue
- Frequent startup issues
- Standing pilot system (needs annual service)
- Higher than normal gas bills
Preventing Furnace Startup Problems in Portland
Pre-Heating Season (September-October)
- • Schedule professional annual tune-up
- • Test carbon monoxide detector
- • Check thermostat batteries
- • Inspect visible gas lines for damage
- • Clean furnace area and ensure clearance
During Heating Season
- • Change air filters monthly
- • Monitor for unusual sounds or smells
- • Keep emergency numbers handy
- • Know location of gas shutoff and breaker
- • Avoid setting thermostat too low
Portland-Specific Startup Prevention
- • October "first cold snap" often reveals problems after months of inactivity
- • Winter storms can trip breakers - keep emergency shutoff locations marked
- • Older Portland homes may have fuse boxes instead of breakers
- • Standing pilot systems common in pre-1990 homes - annual thermocouple check essential
- • Natural gas systems require proper venting - don't block exhaust or intake
- • Crawlspace furnaces harder to access - professional maintenance critical
Frequently Asked Questions About Furnace Startup Problems
Common causes are tripped circuit breaker, thermostat issues, pilot light out, gas valve closed, flame sensor dirty, pressure switch problems, blown fuse, limit switch tripped, or control board failure. Check power and thermostat first - these fix 70% of no-start issues.
First check circuit breaker at panel. Turn thermostat to lowest setting, wait 30 seconds, turn back up. If electronic ignition, locate reset button on control board (usually red button). If standing pilot, relight pilot light. If these don't work, call professional.
Clicking is usually thermostat relay or gas valve. If clicking but no ignition, check pilot light (standing pilot), flame sensor (electronic), or gas valve. Could also be pressure switch, limit switch, or control board. Clicking without ignition often means safety circuit interruption.
After power outage, furnace may need manual reset. Check circuit breaker, reset thermostat, and relight pilot if standing pilot system. Electronic ignition should restart automatically. If still won't start, control board may need resetting or replacement.
Costs vary: Thermostat $150-350, flame sensor $100-250, igniter $150-400, gas valve $300-600, control board $300-800. Diagnostic fee $100-150 waived with repair. Most ignition issues are $200-500 to fix.
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