Forest River Furnace Not Working: Troubleshooting Guide for RV Owners

The Forest River furnace not working can disrupt travel plans and create uncomfortable conditions in an RV. This article provides practical troubleshooting steps, safety checks, component explanations, and maintenance tips to diagnose and often fix common furnace issues. Follow the guidance carefully and prioritize safety when working with propane and electrical systems.

Symptom	Likely Cause	Quick Action
No power / no lights	Blown fuse, disconnected battery, breaker tripped	Check fuses, battery connections, and shore power
Igniter clicks but no flame	Propane supply, regulator, main gas valve	Verify propane, open valve, inspect regulator
Furnace starts then shuts off	Overheat, blocked vent, bad limit switch	Clear vents, inspect blower, test limit switch
Blower runs but no heat	Failed heat exchanger/ignitor or gas valve	Inspect ignitor, test for gas flow

How Forest River Furnaces Work

Forest River RVs commonly use furnaces made by Suburban or Dometic; they operate on 12V electrical power and propane to produce heat via a combustion chamber and heat exchanger. The thermostat signals the control board to start the ignition sequence, the ignitor or spark lights the burner, and the blower distributes heated air through ducts.

Safety First: Before Touching Anything

Always turn off propane at the tank and disconnect 12V power before inspecting components. Work in a well-ventilated area and use a propane detector if available. If a strong gas smell is present, evacuate the RV and call a qualified technician or emergency services.

Common Symptoms And What They Mean

Identifying the symptom narrows the problem. Common complaints include: complete no-start, clicking ignitor with no flame, furnace runs then shuts off, blower runs but no heat, and unusual noises or smells. Each symptom maps to a set of likely causes and targeted tests.

Basic Troubleshooting Checklist

• Power Supply: Verify the RV battery has adequate charge and connections are clean and tight.
• Fuses and Breakers: Inspect inline fuses and the furnace circuit breaker on DC distribution panels.
• Thermostat: Confirm thermostat settings, batteries (if applicable), and mode (heat).
• Propane Supply: Check tank valve(s), regulator frost/lockup, and other appliances to ensure propane flow.
• Vents and Airflow: Clear intake and exhaust vents from debris, snow, or insect nests.

Electrical Issues To Check

Electrical faults are a frequent cause of furnace failures. Start with the 12V supply: ensure chassis battery or coach battery is charged and charging system is functional. Inspect the furnace’s fuse (often 15A) and the RV’s DC breaker for that circuit. Corroded or loose battery terminals reduce voltage under load and can prevent the ignitor from working.

How To Test 12V Power Safely

Use a multimeter set to 12V DC. Measure voltage at the furnace’s 12V input; it should be above 11.5V during operation. If voltage collapses when the furnace attempts to start, suspect weak battery, poor cable, or high-resistance connection.

Propane System Checks

Confirm the propane tank valve is open and other propane appliances operate. A frozen regulator (icing) can starve the furnace of propane; cycling the tank valve or moving to a warmer environment can help. Inspect the LP hose and fittings for damage and apply a soapy water solution while pressurized to locate leaks.

Ignition And Burner Problems

Forest River furnaces typically use a hot surface ignitor or spark electrode. If the control board attempts ignition but no flame appears, the ignitor may be cracked or the electrode misaligned. Visual inspection can reveal obvious damage; replacement ignitors are common and affordable. Confirm a strong clicking or warm-up period before flame—if there’s none, the control board may be at fault.

Diagnosing The Ignitor And Gas Valve

1. Observe the ignition cycle: is the ignitor heating or is there spark?
2. Listen for the gas valve opening or click; no click suggests valve or control issue.
3. With propane present and ignitor functioning, watch for burner ignition; persistent absence could indicate clogged orifices or insufficient gas pressure.

Limit Switches And Overheat Shutoffs

Furnaces have safety switches that shut the unit down if the heat exchanger overheats. Causes include restricted airflow from blocked return vents, dirty blower wheel, or collapsed ductwork. If the furnace runs briefly then shuts off, inspect air filters, clear inlet screens, and clean the blower and heat exchanger.

Blower Motor And Airflow Troubleshooting

If the furnace blower does not run or runs weakly, check the blower motor, capacitor (if equipped), and wiring. Remove obstructions from the blower area. Test motor operation by applying 12V directly (only if skilled and safe to do so) to isolate motor failure from control issues.

Exhaust And Intake Vent Blockages

External intake and exhaust vents can be blocked by snow, mud, insect nests, or debris. Blockage can prevent combustion and trigger safety shutoffs. Regularly inspect vents and use a flashlight to look deep into the duct for nests or buildup.

Control Board And Error Codes

Many furnaces have LED indicators on the control board that blink diagnostic codes. Consult the furnace manual to interpret the blink patterns; codes often indicate low voltage, flame sense failures, or failed components. Note the code pattern and cross-reference before replacing parts.

How To Read LED Blink Codes

Locate the control board label for the blink code key or check the Forest River/RV furnace manual. Count long and short flashes and pauses; document patterns in sequence. This method prevents unnecessary replacement of parts and points to the failing subsystem.

Seasonal Maintenance To Prevent Failures

• Annual Inspection: Have a qualified technician inspect the heat exchanger, gas valve, and combustion path.
• Clean Vents: Remove debris from intake and exhaust annually and after extended storage.
• Check Battery Health: Maintain battery charge levels and test capacity before winter trips.
• Replace Ignitors And Filters: Replace failed ignitors and clean or replace cabin air filters to maintain airflow.

When To Replace Components

Replace the ignitor if it shows cracks or fails to glow. Replace the blower motor if it runs weakly or makes grinding noises. Replace the control board only after confirming other components and following diagnostic codes, as boards are pricier and can be misdiagnosed.

Parts, Tools, And Cost Expectations

Common replacement parts include ignitors ($20–$60), thermostats ($30–$150), blower motors ($80–$300), and control boards ($100–$400). Essential tools are a multimeter, small socket set, screwdrivers, and a propane leak detector. Labor costs vary by shop and region.

When To Call A Professional

Call a qualified RV technician if there is a strong propane smell, suspected gas leak, cracked heat exchanger, persistent flame failure after basic troubleshooting, or if electrical work beyond fuses is required. Professional service ensures safety and code compliance.

Preventive Tips For Reliable Warmth

• Keep the propane tank full enough to prevent regulator freeze in cold weather.
• Run the furnace periodically during storage to maintain moving parts and detect early issues.
• Use carbon monoxide and LP detectors and test them monthly.
• Document maintenance and part replacements to build a service history.

Troubleshooting Flowchart Summary

Step	Action	Expected Result
1	Verify 12V power and fuses	Furnace powers on
2	Confirm propane tank open and appliances working	Propane available
3	Observe ignition cycle and LED codes	Identify component area
4	Check vents and airflow	No obstructions
5	Replace suspected ignitor or test gas valve	Restored ignition

Frequently Asked Questions

Why Won’t My Furnace Start But The Blower Runs?

When the blower runs without flame, the issue is often with ignition, gas supply, or flame sensing. Inspect the ignitor first, then verify propane flow and clean flame sensor contacts.

How Can A Weak Battery Affect The Furnace?

A weak battery may supply enough power to spin the fan but not enough for the ignitor or gas valve, causing intermittent failures. Test with a fully charged battery or jump the system briefly with care.

Is It Safe To Run The Furnace In Strong Winds Or Snow?

Strong winds and snow can block exhaust or pressurize vents, causing inefficient combustion or shutoffs. Clear vents of snow and avoid running the furnace if the exhaust is obstructed.

Can Insect Nests Really Block A Furnace?

Yes. Mud dauber and wasp nests commonly obstruct intake and exhaust openings, restricting airflow and preventing ignition or causing shutdowns. Regular inspection prevents this problem.

Resources And Manuals

Consult the Forest River RV manual and the specific furnace manufacturer (Suburban/Dometic) manual for model-specific troubleshooting and LED code definitions. Manufacturer support lines and authorized RV service centers provide model-specific diagnostic help and replacement parts.