4021-736 PILOT ASSEMBLY PSE – Natural Gas – Millivolt
4021-736 PILOT ASSEMBLY PSE – Natural Gas – Millivolt
✔ In stock — Usually ships in 1–2 business days
What This Part Does
The 4021-736 pilot assembly is a Natural Gas millivolt (standing pilot) ignition component responsible for lighting the pilot flame and generating the electrical signal required to operate the gas valve.
In a millivolt (standing pilot) system, the pilot flame heats the thermocouple and thermopile. The thermocouple helps keep the pilot gas flow open for safety, while the thermopile generates the millivolt power used to operate the main gas valve.
When a call for heat is made from a wall switch, thermostat, or remote, the thermopile supplies voltage to the gas valve, allowing it to open and deliver gas to the main burner.
This assembly also includes the pilot burner and ignition source, which are responsible for reliably lighting the pilot flame.
Proper pilot assembly operation is essential for safe ignition, consistent voltage generation, and reliable fireplace performance.
Not sure if this is the right part?
Before ordering, check the following:
- Locate your model number (typically behind the lower louver or inside the control compartment)
- Confirm your unit uses a millivolt (standing pilot) system
- Confirm your gas type is natural gas
- Compare your existing pilot assembly to the images provided
⚠️ This part is NOT for IPI (electronic ignition) systems
⚠️ This part is NOT for propane (LP) units
If unsure, refer to your manual or contact us for help identifying the correct part.
🔁 Using propane (LP) instead of natural gas?
This part will not work. View the correct LP version here: 4021-737
Compatible Models
Heatilator Gas Fireplaces:
6000BE
6000BELP
6000CAMP
6000CAMPLP
6000SEB-DSI
6000SEBLP
6000SEBLP-DSI
6000TRB-DSI
6000TRBLP
6000TRBLP-DSI
6000TRI
6000TRILP
6000TRILP-SP
6000TRI-SP
6000TRLP-OAK
6000TRXI
6000TRXILP
6000TVB
6000TVBLP
6000TVLP-OAK
6000TV-OAK
6000XLSBLP
6000XLT-AU
6000XLTB
6000XLTBLP
6000XLT-FF
6000XLTLP-AU
7000TRLP-NF
7000TRLP-NF-DSI
7000TR-NF
7000TR-NF-DSI
7000TVLP-NF
7000TVLP-NF-DSI
7000TV-NF
7000TV-NF-DSI
7000XLSLP-NF
7000XLS-NF
7000XLTLP-NF
7000XLT-NF
8000TRC-DSI
8000TRCLP
8000TRCLP-DSI
8000TRD
8000TRDLP
8000TVC
8000TVC-DSI
8000TVCLP
8000TVCLP-DSI
8000TVD
8000TVDLP
8000TV-OAK
BAY-38HV
BAY-38HV-DSI
BAY-38HVLP
BAY-38HVLP-DSI
BE-32
BE-36
BE-36-C
BE-36LP
BE-41
BE-41B
BE-41LP
BE-41LPB
EVEREST
EVEREST-IPI
EVEREST-LP
EVEREST-LP-IPI
L-COR-TRC
L-COR-TRC-DSI
L-COR-TRC-IPI
L-COR-TRCLP
L-COR-TRCLP-DSI
L-COR-TVFL
L-COR-TVFL-DSI
L-COR-TVFLLP
N4236L
NB3630
NB3933
NB4236
NB4842
ND3630
ND3630L
ND3630M
ND3933
ND3933L
ND3933M
ND4236
ND4236L
ND4236M
ND4842
ND4842L
ND4842M
PIER-38HV
PIER-38HV-DSI
PIER-38HVLP
PIER-38HVLP-DSI
PIER-TRC
PIER-TRC-DSI
PIER-TRC-IPI
PIER-TRCLP
PIER-TRCLP-DSI
PIER-TVFL
PIER-TVFLLP
QV32
QV32-A
QV32LP
QV32LP-A
QV36
QV36-A
QV36D
QV36D-A
QV36DB
QV36DB-IPI
QV36DBLP
QV36DLP
QV36DLP-A
QV36LP
QV36LP-A
QV-PIER
QV-PIERLP
QV-ST
R-3500TRC
R-3500TRHC
R-3500TRH-NL
R-3500TR-NL
R-3500TV-NL
R-3DVFS
R-3DVFS-B
R-4500TRC
R-4500TRHC
R-4500TRH-NL
R-4500TR-NL
R-4500TV-NL
R-5500RHT
R-5500TRC
R-5500TRHC
R-6500TR-NL
R-6500TV-NL
R-COR-TRC
R-COR-TRC-DSI
R-COR-TRC-IPI
R-COR-TRCLP
R-COR-TVFL
R-COR-TVFL-DSI
R-COR-TVFLLP
RST-DVFS-B
SL-350TRS
SL-350TRSLP
SL-350TV
SL-350TV-DSI
SL-350TVLP
SL-350TVLP-DSI
SL-550TR-D
SL-550TR-DSI
SL-550TR-DSI-C
SL-550TRLP
SL-550TRLP-C
SL-550TRLP-D
SL-550TRLP-DSI
SL-550TRS-B
SL-550TRSLP
SL-550TRSLP-B
SL-550TRSLP-C
SL-550TV
SL-550TV-DSI
SL-550TVLP
SL-550TVLP-DSI
SL-750TRFL
SL-750TRFLLP
SL-750TRLP
SL-750TRLP-C
SL-750TRLP-D
SL-750TRLP-DSI
SL-750TRS-B
SL-750TRSLP-B
SL-750TRSLP-C
SL-750TV
SL-750TV-C
SL-750TV-DSI
SL-750TV-DSI-C
SL-750TVLP
SL-750TVLP-DSI
SL-950TR-DSI
SL-950TRLP
SL-950TRLP-DSI
SL-950TV
SL-950TV-DSI
SL-950TVLP
SL-950TVLP-DSI
ST-38HV
ST-38HV-AU
ST-38HV-DSI
ST-38HVLP
ST-38HVLP-AU
ST-38HVLP-DSI
ST-42TVFL
ST-42TVFLLP
ST-TRC
ST-TRC-DSI
ST-TRC-IPI
ST-TRCLP
ST-TRCLP-DSI
Heatilator Gas Inserts:
BAY-INSERTLP-NF
BAY-INSERTLP-NS
BAY-INSERT-NF
BAY-INSERT-NS
CFX-GRANDLP-B
CFX-INLP-B
FB-GRANDLP
FB-INLP
QVI-30FB
R-DVI-NF
Heat-N-Glo Gas Fireplaces:
6000SEB
6000TRB
6000TR-OAK
6000XLSB
8000TRC
8000TR-OAK
BCBV36
CFX-Grand-B
CFX-IN-B
FB-Grand
FB-IN
SL-350TRS-C
SL-550TR
SL-550TR-C
SL-550TRS
SL-550TRS-C
SL-750TR
SL-750TR-C
SL750TRCN
SL-750TR-D
SL-750TR-DSI
Sl-750TR-DSI-C
SL-750TRS-C
SL-950TR
SL-950TR-C
SL-950TR-DSI-C
Heat-N-Glo Gas Inserts:
AT-GRAND-B
AT-GRAND-C
AT-GRAND-D
AT-GRANDLP-B
AT-GRANDLP-C
AT-GRANDLP-D
ATS-AU-D
ATSLP-AU-D
AT-SUPREME-B
AT-Supreme-C
AT-SUPREME-D
AT-SUPREMELP-B
AT-SUPREMELP-C
AT-SUPREMELP-D
AT-ZC-B
AT-ZCLP-B
R-MAXIN
Quadra-Fire Gas Fireplaces:
QV36B
Royal Gas Fireplaces:
R-5500TR
Travis Gas Fireplaces:
DVL-ZC
System Type
This is a millivolt standing pilot system. These systems use a continuously burning pilot flame and do not require household electrical power for basic operation.
Millivolt systems are commonly found in many direct vent gas fireplaces and are known for simple, reliable operation.
This system commonly includes:
- Thermocouple — helps keep the pilot gas valve open when the pilot flame is proven.
- Thermopile — generates millivolt power used to operate the main gas valve.
- Igniter electrode — provides manual spark ignition, usually from a push-button piezo igniter.
- Pilot tube — delivers gas from the valve to the pilot assembly.
Because these systems do not rely on external power, they can often operate during a power outage when used with a manual switch or compatible battery-free control setup.
These systems offer improved efficiency, remote-control compatibility, and added safety features, but they also include more electronic components than a millivolt system.
Common Problems This Part Fixes
If your fireplace uses a millivolt (standing pilot) system, the pilot assembly is responsible for generating the voltage needed to operate the gas valve and proving flame safety. When it begins to fail, it can cause a range of ignition and operating issues.
Replacing the pilot assembly often resolves the following problems:
- Pilot will not stay lit
A weak or failing thermocouple may not keep the gas valve open. - Pilot lights but goes out when the knob is released
The thermocouple is not properly generating or delivering a safety signal. - Pilot flame is weak, small, or unstable
A clogged pilot orifice or worn components can affect flame quality. - Burner will not turn on even though pilot is lit
A weak thermopile may not generate enough voltage to operate the valve. - Intermittent operation or delayed burner ignition
Inconsistent voltage output from the pilot assembly can cause unreliable performance. - No response from wall switch or remote
Insufficient millivolt output can prevent the system from activating. - Difficulty lighting the pilot
A worn igniter electrode or misaligned pilot components can prevent proper ignition.
Important Note
Many of these symptoms can also be caused by a faulty gas valve, loose wiring, or improper gas pressure. Proper diagnosis is recommended before replacing the pilot assembly.
Warranty Information
This product includes a 12-month warranty from the date of purchase. This warranty covers defects in materials or workmanship under normal operating conditions.
Fireplace components must be properly installed and matched to the correct system (millivolt vs IPI, natural gas vs propane).
This warranty does NOT cover:
• Improper installation or incorrect application
• Use with the wrong gas type (NG vs LP)
• Misdiagnosis of the issue
• Damage caused by other failing components
• Normal wear and tear
• Labor, service, or diagnostic time
Because many fireplace issues can be caused by multiple components, we strongly recommend confirming the diagnosis before replacing parts.
We are happy to assist with this. Proof of purchase is required for all warranty claims. Please contact us prior to removal or replacement of the part so we can help verify the issue and guide the warranty process.
Do I need any special tools to install this?
Most pilot assemblies can be installed using basic hand tools, and no specialized equipment is typically required.
In most cases, you will need:
• Adjustable wrench or open-end wrenches
• Screwdrivers (Phillips and/or flathead)
• Nut driver or socket set
The pilot assembly is usually mounted near the burner and connected by a pilot tube and thermocouple or thermopile. Installation involves removing the old assembly, reconnecting the gas line components, and securing the new pilot in place.
It is important to ensure all connections are tight and properly aligned. After installation, always check for gas leaks using a leak detection solution and confirm proper pilot flame appearance.
If you are unsure or uncomfortable working with gas components, we recommend having a qualified technician perform the installation to ensure safe and proper operation.
Do I need to make any adjustments after installation?
In most cases, no major adjustments are required after installing a pilot assembly, but a few important checks should always be performed to ensure proper operation.
After installation, you should:
• Verify the pilot flame is steady and properly positioned over the thermocouple or flame sensor
• Confirm the flame is strong enough to fully engulf the sensor (not weak or lifting)
• Check all gas connections for leaks using a leak detection solution
Some systems may include a pilot adjustment screw on the gas valve. If needed, this can be used to fine-tune the pilot flame height, but many modern systems are preset and do not require adjustment.
If the pilot flame appears weak, unstable, or does not stay lit, this may indicate an issue with gas pressure, air in the line, or another component in the system.
Proper flame appearance and stable operation are key to safe and reliable performance. If you are unsure about flame characteristics or adjustments, we recommend consulting a qualified technician.
How difficult is this part to replace?
Replacing a pilot assembly is generally considered a moderate repair and can often be completed by a homeowner with basic mechanical skills.
The process typically involves accessing the burner area, disconnecting the pilot tube and sensor leads, removing the old assembly, and installing the new one in the same position.
While no specialized tools are usually required, the work does involve gas connections and components that must be installed correctly to ensure safe operation.
For someone comfortable working with hand tools and following instructions carefully, this is a manageable repair. However, access to the pilot assembly can vary depending on the fireplace model, and some units may require additional disassembly.
If you are unsure about working with gas systems or identifying proper flame characteristics after installation, we recommend having a qualified technician perform the replacement.
How do I know if my pilot assembly is bad?
A bad pilot assembly will usually show clear symptoms related to ignition problems or unstable flame performance.
Common signs of a faulty pilot assembly include:
• Pilot will not light at all
• Pilot lights but will not stay lit
• Weak, small, or flickering pilot flame
• Pilot lights but the main burner does not turn on
• Intermittent operation or frequent shutdowns
In many cases, the issue is caused by a worn or failing thermocouple or thermopile, a clogged pilot hood, or a damaged ignition component. Dirt, dust, or corrosion can also affect how the pilot flame contacts the sensor.
A proper pilot flame should be steady, strong, and fully engulf the thermocouple or flame sensor. If the flame is weak, not making good contact, or going out unexpectedly, the pilot assembly may need to be cleaned or replaced.
Before replacing the assembly, it is also important to rule out other possible causes such as low gas pressure, air in the gas line, or a faulty gas valve.
If cleaning does not resolve the issue or the components show signs of wear or damage, replacing the pilot assembly is often the most reliable solution.