Intertherm Furnace Troubleshooting Manual

The Intertherm Furnace is a reliable heating system designed for residential use, featuring efficient heat exchange technology, electronic ignition, variable-speed blower motor, safety controls, and diagnostic LED indicators. This manual provides comprehensive troubleshooting guidance for common furnace issues, maintenance procedures, and safety information to ensure optimal performance and longevity of your heating system.

1. Safety Precautions 2. Common Symptoms & Solutions 3. Diagnostic LED Codes 4. Component Testing 5. Maintenance Procedures 6. Electrical Specifications 7. Gas Valve Operation 8. Blower Motor Issues 9. Thermostat Problems 10. Professional Service 11. Emergency Procedures

Safety Precautions

Before troubleshooting, ensure safety protocols are followed to prevent injury or damage to the furnace.

Safety Measure	Description
Power Disconnect	Turn off electrical power at service panel before inspection
Gas Valve Shutoff	Close gas supply valve before working on gas components
Carbon Monoxide	Install CO detectors near furnace area
Clearance Space	Maintain minimum 18-inch clearance around furnace
Ventilation	Ensure proper airflow and venting
Professional Help	Contact qualified technician for complex issues

Common Symptoms & Solutions

Identify and resolve frequent furnace problems with these troubleshooting steps.

Furnace won't start: Check thermostat setting, power supply, and circuit breaker.
No heat production: Verify gas supply, pilot light, and ignition system.
Short cycling: Inspect air filter, thermostat location, and flame sensor.
Blower runs continuously: Check thermostat fan setting and limit switch.
Unusual noises: Examine blower wheel, motor bearings, and heat exchanger.

WARNING! Always disconnect power before inspecting electrical components. Gas leaks require immediate professional attention.

Diagnostic LED Codes

The furnace control board displays LED flash codes to indicate specific issues.

Flash Pattern	Description	Action Required
1 Flash	Pressure switch stuck open	Check venting and pressure switch tubing
2 Flashes	Rollout switch open	Inspect heat exchanger and flame rollout
3 Flashes	Limit circuit open	Check airflow and filter restriction
4 Flashes	Ignition failure	Verify gas supply and igniter operation
5 Flashes	Pressure switch stuck closed	Inspect pressure switch and vent motor

Component Testing

Proper testing procedures for critical furnace components.

Thermostat: Check for 24V between R and W terminals
Limit Switch: Should show continuity when cool
Flame Sensor: Clean with emery cloth if dirty
Igniter: Resistance should be 40-90 ohms
Gas Valve: Verify 24V signal to valve coil
Blower Motor: Check capacitor and windings

Maintenance Procedures

Regular maintenance ensures efficient furnace operation and prevents common issues.

Monthly: Check and replace air filter if dirty
Seasonal: Inspect vent pipes for obstructions
Annual: Clean flame sensor and burners
Annual: Lubricate blower motor if required
Annual: Check heat exchanger for cracks

CAUTION! Only qualified technicians should perform internal furnace maintenance.

Electrical Specifications

Power Supply: 120V AC, 60Hz
Control Voltage: 24V AC transformer
Blower Motor: Variable speed ECM or PSC
Igniter: Silicon nitride hot surface igniter
Amperage Draw: 5-15 amps depending on model
Circuit Protection: 15-20 amp breaker required

Gas Valve Operation

The gas valve controls fuel supply to the burners and requires proper testing.

Check inlet gas pressure: Should be 7-11 inches WC
Verify outlet pressure: Typically 3.5 inches WC
Test valve solenoid: 24V should open valve
Inspect for leaks: Use bubble solution on connections

WARNING! Gas valve adjustments should only be made by qualified technicians.

Blower Motor Issues

Common blower motor problems and solutions.

Symptom	Possible Cause	Solution
Motor won't start	Bad capacitor or winding	Test capacitor; check for open windings
Motor noisy	Worn bearings or debris	Lubricate or replace motor; clean blower wheel
Motor runs slow	Weak capacitor or voltage drop	Replace capacitor; check voltage supply
Motor overheats	Restricted airflow	Clean filter and ductwork

Thermostat Problems

Troubleshooting common thermostat-related issues.

No display: Check batteries and 24V power
Inaccurate temperature: Relocate thermostat away from heat sources
Short cycling: Adjust anticipator setting
No communication: Check wiring connections at furnace and thermostat

Professional Service

When to contact a qualified HVAC technician.

Gas leak detected (smell of rotten eggs)
Heat exchanger visible cracks or damage
Carbon monoxide detected
Electrical issues beyond basic troubleshooting
Repeated lockout or error codes

Service Contact: 1-800-INTERTHERM or visit www.intertherm.com

Emergency Procedures

Immediate actions for furnace emergencies.

Emergency	Immediate Action	Follow-up
Gas smell	Evacuate immediately; call gas company	Do not operate electrical switches
Smoke from furnace	Turn off power at breaker	Contact fire department if necessary
CO alarm sounds	Evacuate; open windows	Call emergency services
Water leakage	Turn off power and water supply	Check for condensate line blockage

Emergency Numbers: Gas Company: [Local Number], Fire Department: 911