Commercial Gas Griddle Troubleshooting Guide

A griddle with a cold corner and a scorching centre wrecks consistency — the same burger cooks two different ways depending on where the chef puts it. It is also one of the most misdiagnosed faults in a commercial kitchen, because the advice you'll find first is usually the least likely cause.

This guide runs the checks in the order that actually finds the fault. For the parts, see all gas equipment parts.

Why is my gas griddle heating unevenly?

Work through these four in order. The first two account for most genuine faults.

1. The thermostat capillary bulb has come out of its clamp

This is the one that catches people out, and it is worth checking first because it costs nothing.

On a thermostatic griddle, the thermostat senses temperature through a capillary bulb clamped tight against the underside of the griddle plate. Contact is everything: the bulb must be touching steel to read plate temperature.

If that clamp works loose — and vibration, cleaning and years of heat cycling all loosen it — the bulb ends up hanging in the air under the plate. It now reads the cooler air temperature, decides the griddle is nowhere near setpoint, and holds the burner on at full rate. The result is a severe hot spot directly above that burner while the thermostat still thinks it is under temperature.

Check: with the griddle cold and isolated, look underneath. The bulb should be firmly held against the plate, not dangling. Re-seat it in its clamp and a large share of "uneven heat" complaints disappear.

2. Blocked or worn burner jets

Griddles run under a plate that drips fat continuously. Grease, carbon and food debris partly block burner ports and jets, which cuts the gas rate to that section of burner. Less gas there means less heat there — exactly the cold patch you're seeing.

Check with the flame, not the food. Run the burner and look along its length:

• Even crisp blue the whole way — burner is fine, look elsewhere
• Dead or weak sections — blocked ports, clean them out
• Yellow or lazy flames — aeration or jet problem, see below

Jets that are eroded, corroded or have been drilled out at some point in the past should be replaced rather than cleaned — once the orifice size is wrong, the gas rate is wrong permanently.

3. The griddle isn't level

Worth checking because it takes a minute, and on griddles it matters more than on most equipment — fat and oil pool at the low end and change how heat transfers there. Check side-to-side and front-to-back and adjust the feet.

It is a real cause, just not usually the main one on a commercial unit that has been in place for years and was level when it was cooking properly. If the unit hasn't moved and the heat has changed, look at the bulb and the jets.

4. The thermostat is out of calibration

If the bulb is properly clamped, the burner flame is even, and the unit is level, the thermostat itself may be reading wrong. Verify before replacing: heat the griddle to a set temperature, let it cycle, and check the plate with an infrared or probe thermometer at several points.

Why won't my gas griddle light?

Same chain as any commercial gas appliance. Check gas supply first — is the isolation valve fully open, and is other gas equipment working?

Then the pilot system:

On a griddle specifically, the pilot assembly sits directly under a plate that sheds fat onto it all day. Blocked pilot orifices are far more common here than on other equipment, and cleaning the pilot is always worth doing before condemning parts.

Why won't my griddle hold its set temperature?

If the plate gets hot but drifts, overshoots, or crashes when you load it, the fault is in temperature control rather than the burner.

• Capillary bulb loose or out of position — as above, the first thing to check
• Capillary kinked or fractured — the fluid inside is what drives the thermostat. Lose it and the thermostat fails, usually to fully open (griddle runs flat out) or fully shut (no heat at all). A kinked capillary cannot be repaired
• Thermostatic valve failed — on griddles the temperature control is often a thermostatic gas valve rather than a separate stat. If the valve no longer modulates, it can only be on or off
• Undersized for the load — a griddle that holds fine when idle and crashes under a full load is being asked to do more than its gas rate allows. That's not a fault

Always verify with a thermometer before ordering a replacement thermostat. Chefs judge griddle temperature by feel and habit, and "it's not hot enough" is sometimes a setpoint change nobody mentioned.

Why is my griddle flame yellow?

Griddle burners should burn blue. Yellow, soft or lifting flames mean the air-to-gas mixture is wrong, and that produces carbon monoxide as well as poor heat.

Causes in order:

• Air shutter on the venturi closed too far — starves the burner of primary air, giving soft yellow flames that soot everything
• Grease or debris in the venturi — same effect, common on griddles
• Blocked or wrong burner jets
• Wrong jet for the gas type after a conversion
• Supply pressure wrong — needs a manometer and an engineer

Yellow flames with sooting is a fault to act on, not to live with. Isolate the appliance and get it checked.

Why does the griddle control knob spin or feel loose?

Almost always the knob rather than the valve. Griddle knobs sit right in the heat and grease path, and the plastic splines soften and round off. Once rounded, the knob turns without moving the spindle. Replacement control knobs are among the cheapest parts on the machine.

If the spindle itself is stiff, sloppy, or gas passes when the tap is off, the valve body is at fault and needs replacing.

What gas pressure should a UK griddle run at?

Most griddle troubleshooting content online is American and quotes inches of water column. In the UK, commercial catering appliances are set up around 20 mbar for natural gas and 37 mbar for propane (LPG), and the correct figure with the correct injector marking is on your appliance data plate.

Threads here are BSP, not the NPT sizes on US listings — check before ordering gas pipe fittings. Converting between natural gas and LPG means changing injectors and re-commissioning: Gas Safe work.

How do I stop uneven heating coming back?

Griddle faults are overwhelmingly grease faults. A short routine prevents most of them:

• Clear the grease trough and drain properly every day — what overflows ends up on the burners and pilot
• Check the burners and pilot assembly for grease build-up on your deep-clean cycle, not only when something breaks
• After any strip-down or deep clean, confirm the capillary bulb went back into its clamp. This is the single most common way a working griddle becomes an uneven one
• Keep the unit level

Can I repair a commercial gas griddle myself?

Diagnose freely — checking the bulb clamp, looking at flame quality, cleaning grease off burners, levelling the unit and verifying plate temperature are all reasonable in-house jobs.

Fitting gas parts is not. In the UK, work on commercial catering gas appliances must be carried out by a Gas Safe registered engineer holding the commercial catering qualifications. That covers gas valves, injectors, burners and pilot assemblies. Work out what's failed, order the right part, have it fitted and tested.

Frequently asked questions

Why does my griddle have one permanent hot spot?

A single fixed hot spot above one burner is the signature of a capillary bulb that has come away from the plate in that zone. The thermostat never sees the plate get hot, so that burner never throttles back.

Should I level my griddle or replace parts first?

Level it first — it takes a minute and costs nothing. But if the griddle used to cook evenly in the same position and now doesn't, levelling is unlikely to be your answer. Check the bulb and the burner flame.

Can I clean burner jets instead of replacing them?

Cleaning is worth doing and often restores the burner. Replace the jet when it is eroded, corroded, or has been drilled out at some point — once the orifice size has changed, the gas rate is permanently wrong and no cleaning fixes it.

My griddle takes forever to heat up — is that a fault?

Check flame quality first. A burner running weak across its whole length points to gas rate: blocked jets, restricted supply, or low pressure. If the flame looks strong and even, the griddle may simply be recovering from a heavy load, which is normal.

How fast can I get a griddle part?

We hold genuine replacement gas parts in UK stock. Order before 10am for next-day delivery, free over £25. Call 073 8051 5838 with your griddle make, model and the number on the old part and we'll match it.

Need help identifying the part?

Send a photo of the thermostat, valve or data plate and we'll tell you what it is.

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