Fryer pilot won't stay lit
A standing pilot that goes out the moment you release the knob is telling you one specific thing: the safety valve is not getting enough electricity from the flame to stay open. Most of the time that is a lighting technique, a flame, a connection or a high limit, not a new gas valve.
Stop. Don't light anything or operate switches near the fryer. Turn the fryer's gas valve off, ventilate, and call your gas utility or a gas technician. Pitco's manuals also require a 5-minute wait before relighting a pilot that has gone out, so any gas inside the fryer can clear.
How a standing pilot stays lit
On a millivolt fryer — Pitco SG14, SG18, 35C+, 45C+, Dean and Frymaster SM series and most basic gas fryers — the pilot heats a small sensor. Pitco uses a thermopile; Dean and Frymaster's millivolt fryers use a thermocouple. Heated by the flame, it produces a tiny voltage, measured in thousandths of a volt, which holds the gas valve open. While you hold the knob in, you are holding the valve open by hand. Let go, and if the sensor isn't producing enough voltage, the valve closes and the pilot goes out.
So "lights but won't stay lit" is almost never a gas supply problem. Gas is clearly getting there. The question is why the sensor isn't producing or delivering enough voltage.
Models with a controller and electronic ignition, such as the Pitco SGH50, have no standing pilot to light by hand. Their ignition module sparks for about 90 seconds, then locks out if it doesn't sense a flame, and the controller shows HEAT FAIL or IGNITION FAILURE. Pitco's service manual says to check, in order, the high limit, the ignition module, then the heat demand relay. The high limit section below applies to them too.
First: are you lighting it the way Pitco specifies?
From Pitco's installation and operation manual for SG-series fryers:
- The tank must be full of oil before the valve is ever turned to ON.
- Turn the gas valve knob to PILOT, push it in, and light the pilot.
- Keep holding the knob in for 60 seconds after the pilot lights.
- Release. The pilot should stay lit.
Sixty seconds is longer than most people hold it. The sensor needs that time to heat up and produce enough voltage, so letting go after 10 or 15 seconds is the most common reason a perfectly good pilot goes out. After gas work, or with air in the line, Pitco's 35C+/45C+ manual says to hold the knob in for about a minute before lighting to purge the air, and that first ignition may take a while.
If it goes out: wait 5 minutes and try again. Pitco says that after three failed attempts you stop and troubleshoot.
Match the symptom to the cause
| What happens | Where to look |
|---|---|
| No flame at all when you press and light | Gas valves closed (the building supply and the fryer's own valve), no gas reaching the fryer, or a pilot orifice or supply line blocked with dirt or lint |
| Lights, goes out the moment you release | Knob not held long enough, flame too small to heat the sensor, a loose or dirty sensor connection at the gas valve, a weak thermopile or thermocouple, or a tripped high limit |
| Stays lit, goes out later or during service | Draughts from air conditioning, make-up air or the hood blowing the flame off the sensor; a high limit tripping as the oil heats; low gas pressure |
| Pilot stays lit, burners won't come on | Thermostat set too low or faulty, high limit open, or the gas valve's main side — see below |
The checks, in order
1. The pilot flame
The flame has to wrap around the sensor. Dean and Frymaster's millivolt manual gives a target of about ¾ inch above the pilot burner, and calls out a flame that wavers and doesn't fully envelop the thermocouple as its own fault. Pitco's manual shows the same thing in a picture: a flame too small to produce enough voltage, next to one the right size. A weak, lazy or yellow flame usually points to a dirty pilot orifice. Adjusting the flame is done at a screw on the gas valve; on Pitco, clockwise lowers the flame and the output.
2. Draughts
Dean's first remedy for an unstable flame is to look for air conditioning or make-up air equipment blowing across the fryer, turn it off, and watch the pilot again. A pilot that only goes out when the hood fans are on high, or when the back door is propped open, is a draught problem, not a parts problem.
3. The connection at the gas valve
The sensor lead screws into the gas valve. Dean and Frymaster's troubleshooting is to check it is screwed in properly, then remove it and clean the end with fine sandpaper or emery cloth, and check all connections for cleanliness and security. Grease and heat oxidise these contacts, and a few millivolts lost at a dirty contact is enough to drop the valve.
4. The high limit
The high limit is the safety switch that shuts off gas if the oil gets dangerously hot. In Pitco's 35C+/45C+ manual, the thermopile is tested with a meter on one of the high limit terminals — the high limit sits in the same low-voltage circuit as the pilot sensor. A tripped or faulty high limit breaks that circuit, so the valve can't hold.
Resetting it: Pitco's quick guide says to open the fryer door, find the gas valve, and feel on top of the box labelled high limit reset for a red button. Push it down and release. Let the fryer cool first; the switches sit near the burners.
On the electronic SGH50, Pitco's service manual gives the trip point as 450°F ± 15°F, and says the switch won't reset until the oil has cooled to about 400°F. If it still won't reset once cool, the switch is defective.
It means the oil really is getting too hot, or the switch is failing. Pitco's manual says that if the burners don't turn off at the lowest thermostat setting, the thermostat could be defective. Overheated oil is a fire risk. Stop using the fryer and call for service rather than resetting it again.
5. The thermopile or thermocouple itself
When the flame is right, there's no draught, the connection is clean and the high limit is fine, the sensor is the next suspect. Pitco's 35C+/45C+ manual gives the numbers a technician works to:
| Measurement | Pitco specification |
|---|---|
| Acceptable thermopile output | 300–500 mV |
| Target when adjusting the pilot | 400 ± 50 mV |
| Meter | DC millivolts, 0–1000 mV scale |
| Where to measure | Negative to the pilot bracket, positive to a high limit terminal |
| Between adjustments | Wait 3–5 minutes for the reading to settle |
Low output with a good flame means a worn sensor. A thermopile and a thermocouple are different parts, and many fryers use one or the other, so order by your model number.
6. Gas pressure and the gas valve: technician territory
If everything above checks out, what's left is gas pressure and the combination gas valve. Pitco specifies supply pressure of 7.0 ± 2.0 inches water column for natural gas and 12.0 ± 2.0 for LP, with manifold pressure matching the data plate inside the door. Measuring and adjusting gas pressure, and replacing a gas valve, are jobs for a qualified gas technician.
Things that look like faults but aren't
- The first light after gas work takes a long time. Air in the line. Pitco expects it.
- The burners cycle off while the pilot stays lit. That's the thermostat doing its job.
- It won't light straight after going out. The 5-minute wait is a safety requirement, not a fault.
Pitco also says a fryer should never be left in standby overnight — pilot on, burners off. Shut it down completely.
For problems beyond the pilot on a Pitco — HEAT FAILURE or DRAINING messages, a fryer that won't drain, or a filter that won't return oil — see Pitco fryer troubleshooting.
What to tell the technician
- Make, model and serial number, from the data plate inside the door.
- Natural gas or LP.
- Exactly what happens: no flame at all, goes out on release, or goes out later.
- Whether the high limit was tripped, and how often.
- Whether it happens with the hood or air conditioning running.
- On a controller model, the message on the display.