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Millivolt Gas Fireplace Troubleshooting Guide

Support for Homeowners | Gas Fireplace Services – Huntsville, AL

What is a Millivolt Gas Fireplace?

A millivolt system uses a small flame (pilot) to power the gas valve — no household electricity required. If the flame gets weak or something interrupts the signal, the burner won’t light or stay on.

This guide helps you safely diagnose common issues before scheduling a service visit.

Common Symptoms

• Burner won’t turn on
• Pilot won’t stay lit
• Fireplace shuts off shortly after lighting
• Switch works sometimes, not always
• Weak yellow pilot flame

Quick Safety Rules

• If you smell gas — stop and call a professional
• Always turn off gas before cleaning parts
• Never modify gas pressure or orifices yourself

DIY Troubleshooting Checklist

1️⃣ Verify Gas Supply

• Ensure the manual shut-off valve is fully open
• If other gas appliances are running, turn them off temporarily
• If recently installed or serviced — confirm correct gas type (LP vs NG)

What success looks like: strong pilot flame when lit

2️⃣ Inspect the Pilot Flame

Remove glass or access panel for a clear view.

✔ Healthy flame = steady, mostly blue, directly heating the thermopile tip
✘ Poor flame = small, yellowish, flickering away

If weak → move to cleaning below

3️⃣ Clean Pilot & Thermopile

Turn gas OFF before touching.

• Brush pilot assembly gently
• Blow compressed air into pilot tube/orifice
• Clean thermopile tip with a soft brush or fine steel wool
• Make sure flame contacts the sensor directly

If pilot strengthens — relight and test burner

4️⃣ Test the Thermopile (If You Have a Multimeter)

With the pilot lit for 3–5 minutes:

• Set meter to DC millivolts (mV)
• Measure between TP and TH/TP terminals on the valve

Good reading: 400 mV or higher
(below that → replace thermopile)

5️⃣ Check Low-Voltage Wiring

Inside the firebox or behind a wall switch:

• Wires snug?
• Free of corrosion?
• Wall switch/remote working every time?

If jumping TH to TH/TP fires the burner → switch/wiring is the culprit.

Still Not Working?

Likely causes:
• Faulty gas control valve
• Internal blockage
• Wrong gas pressure
• Failed safety components

These require a licensed professional.

When to Call Gas Fireplace Services

If you reach Step 3 or beyond and still have problems — we help homeowners fix:

• Pilot won’t stay lit
• Burner won’t fire
• Flame quality issues
• Annual safety inspections
• Thermopile & thermocouple replacement
• Cleaning & tune-ups

📌 Same-Week Appointments
📌 Straightforward Pricing
📌 Safety Comes First

📞 256-631-7399
📍 Huntsville & North Alabama
📝 Book online: https://huntsvillegasfireplaceservice.com/

Prevent Future Problems

Recommended once per season:

• Clean pilot & burner
• Check flame color
• Clean glass and log soot
• Test CO detectors
• Verify vent/chimney airflow (if vented)