Water Heater and Furnace Not Working: Troubleshooting and Practical Fixes

When a water heater and furnace not working occurs together, it creates urgent discomfort and safety concerns. This guide helps homeowners diagnose common causes, perform safe basic troubleshooting, and decide when to call a professional. It focuses on practical steps for gas and electric systems while highlighting safety precautions and typical repair costs.

Issue	Quick Check	Likely Cause
Both systems dead	Check main breakers and gas supply	Power outage, tripped breaker, gas shutoff
Water cold, no furnace heat	Check pilot, thermostat, breakers	Gas valve, ignition, thermostat, control board
Burner won’t ignite	Inspect pilot/electronic ignitor, gas supply	Faulty ignitor, clogged pilot, gas valve failure

How To Approach A Dual Failure Safely

The first priority when a water heater and furnace not working is safety. Confirm whether the issue is electrical, gas, or both. Shut off power and gas before inspecting equipment. Avoid home repairs if the homeowner smells gas, sees soot, or detects carbon monoxide alarms. In those cases, evacuate and call emergency services and the gas company.

Common Causes When Water Heater And Furnace Not Working

Several shared causes can make both appliances fail simultaneously, including main electrical panel issues, a tripped whole-house circuit breaker, or a closed gas valve. Other causes are independent failures that coincidentally occur at the same time.

• Electrical Supply Problems: Tripped breakers, blown fuses, or a power outage.
• Gas Supply Issues: Closed gas shutoff, supply interruption, or meter problems.
• Safety Devices: Blown thermal fuses, limit switches, or flame rollout switches.
• Control Failures: Faulty thermostats, control boards, or ignition components.

Troubleshooting A Water Heater Not Working

Initial Safety And Checks

Turn off power at the breaker for electric water heaters. For gas units, set the gas control valve to “off” if smell of gas is present.

Electric Water Heater Steps

1. Check the circuit breaker for a tripped breaker and reset it if safe. Do not reset repeatedly.
2. Test the heating elements and thermostat with a multimeter if comfortable; replace a failed element.
3. Inspect the high-limit (thermal) switch on the thermostat assembly; replace if open.
4. Flush the tank to reduce sediment if the heater sputters or underheats.

Gas Water Heater Steps

1. Confirm the gas valve is open and other gas appliances work.
2. Inspect the pilot light or electronic ignition. Relight the pilot following the manufacturer’s instructions or replace a faulty ignitor.
3. Check the thermocouple/thermopile; replace if it no longer senses flame.
4. Examine the gas control valve and burner for clogs; clean burner assembly and venting.

Signs That Point To A Water Heater Replacement

• Repeated component failures, extensive corrosion, or a leaking tank indicate replacement is more economical.
• Age over 10–15 years for conventional tanks often signals imminent failure.

Troubleshooting A Furnace Not Working

Initial Safety And Checks

Confirm the thermostat is set to heat and the temperature setting is above room temperature. Verify the furnace switch (looks like a light switch) is on and check the dedicated furnace breaker.

Gas Furnace Common Troubleshooting

1. Check for a gas supply: try another gas appliance. If none work, contact the gas utility.
2. Inspect the pilot (older units): relight per the manual. For electronic ignition systems, watch for the ignitor glow or click sequence.
3. Clean or replace the air filter; a clogged filter can cause safety lockouts.
4. Look at the condensate line and float switch on high-efficiency furnaces; blockages can trigger shutdowns.
5. Check the furnace error code LED on the control board (refer to manual) to pinpoint issues.

Electric Furnace And Heat Pump Considerations

For electric furnaces or heat pumps, verify the disconnect switch, breakers, and thermostat wiring. Heat pump reversals or defrost issues can mimic heating failure; ensure the system mode is correct.

Common Faulty Components

• Ignitor or pilot assembly
• Gas valve
• Blower motor or capacitor
• Control board or safety switches
• Thermostat misconfiguration or failed sensor

Diagnosing When Both Systems Are Down

If a water heater and furnace not working occur simultaneously, start at the source: house power and gas supply. Confirm other major appliances receive power and verify the gas meter and main shutoff. If both utilities are fine, investigate individual appliance breakers and equipment switches.

When To Call A Professional

Call a licensed HVAC or plumbing technician when any of the following occur: persistent gas odor, visible damage or soot, failed ignition that the homeowner cannot safely test, electrical wiring concerns, or when repairs require a gas valve, refrigerant handling, or control board replacement.

• Safety Risks: Gas leaks or carbon monoxide issues require immediate professional response.
• Complex Repairs: Control board, gas valve, and sealed combustion or heat exchanger repairs need certified technicians.

Estimated Repair Costs And Timeframes

Costs vary by region and system type. Below are average U.S. ranges for common repairs and typical timelines.

Repair	Typical Cost	Typical Time
Reset breaker/reprogram thermostat	$0–$150	30–60 Minutes
Replace heating element or thermocouple	$100–$400	1–2 Hours
Ignitor or control board replacement	$200–$800	1–3 Hours
Gas valve replacement	$300–$900	1–4 Hours
Water heater or furnace replacement	$900–$6,000+	4–8 Hours

Preventive Maintenance To Avoid Future Failures

Regular maintenance reduces the chance that a water heater and furnace not working will happen unexpectedly. Annual inspections and seasonal maintenance are recommended for safe, efficient operation.

• Schedule annual HVAC tune-ups before heating season.
• Flush water heaters annually to remove sediment buildup.
• Replace HVAC and water heater filters regularly and use correct sizes.
• Test carbon monoxide detectors monthly and replace batteries yearly.
• Keep vents and combustion air openings clear and unobstructed.

DIY Checklist Before Calling A Technician

Completing a short checklist helps technicians diagnose faster and may resolve simple issues without a service call.

1. Verify power at main panel and appliance breakers.
2. Ensure gas valve(s) are open and other gas appliances work.
3. Replace or inspect furnace and water heater filters.
4. Check thermostat batteries and settings.
5. Look for error codes or indicator lights on equipment and note them.

Frequently Asked Questions About Simultaneous Failures

Can a tripped main breaker shut down both systems?

Yes. A tripped main breaker or subpanel breaker can disable both the furnace and an electric water heater or the control circuits that manage gas ignition systems.

Is it common for gas supply issues to affect both appliances?

Yes. If the gas company shuts supply or the home gas shutoff is closed, both gas-fired appliances will fail to operate. Always verify other gas appliances before troubleshooting individual units.

How urgent is it if both systems stop working during extreme weather?

Very urgent. Lack of heat during cold weather can create health and safety risks. Use safe alternative heating methods, keep pipes from freezing, and contact a licensed technician promptly.

Are combined electrical and gas failures more likely to be wiring-related?

Not necessarily. Combined failures often trace to utility-level issues (outage or gas supply) or common safety devices like a service disconnect. A qualified electrician or HVAC technician can determine the root cause.

Preparing For The Service Call

When contacting a technician, provide clear details: model numbers, age of equipment, observed symptoms, any odor of gas, and results from the DIY checklist. This helps ensure the technician brings proper parts and offers accurate time and cost estimates.

Key Action Items: Check breakers and gas supply first, replace simple filters or batteries, and never ignore a gas smell or CO alarm. For complex or dangerous issues, call a licensed professional immediately.