LPG Bain Marie Won’t Heat or Pilot Goes Out? Fixes & Spares
Last updated: July 2026
In 30 seconds:
- Most “broken” LPG bain maries are one of three things: air in the pipe, a released tap that needed a 15–20 second hold, or a shifted thermocouple.
- Safe first checks: cylinder valve open, cylinder not empty, regulator seated, five-minute wait between attempts.
- Water not hot enough usually means low water, a knob off the 90 max position, or limescale on the tank base.
- If you smell propane, shut the cylinder valve and stop — leaks are engineer territory, immediately.
- Don’t dismantle anything: the manual says stop using the unit and get professional repair for genuine faults.
It’s 11:40, the queue starts at twelve, and the bain marie won’t light. This guide works through the faults that actually stop an LPG bain marie in a food van — what you can safely check yourself, what each symptom means, and when to hand it to an engineer.
The two failure points the Infernus gas bain marie manual plans for — failed ignition and a flame that dies straight after lighting — cover the overwhelming majority of real-world faults on these units, and both usually have owner-level causes. The checks below follow the manual’s own fault-finding table for the LPG units we stock.
Read this first. Owner-level troubleshooting means checks — not repairs. The manual is explicit: in case of breakdown, do not disassemble the appliance; stop using it and have it repaired professionally. Anything involving the burner, valve, injector or thermocouple is a Gas Safe registered engineer’s job, and if you ever smell propane, close the cylinder valve and stop there.
Safe First Checks (Two Minutes, No Tools)
Step 1: Confirm Propane Is Actually Reaching the Unit
Cylinder valve fully open, cylinder has propane in it, regulator seated properly on the valve, hose not kinked or trapped. An empty or half-closed cylinder is the most common “fault” in mobile catering.
Step 2: Reset the Lighting Sequence
Turn the tap back to the off position, wait five minutes, then run the full sequence again: tap pushed in and turned anti-clockwise, red ignitor pressed until the pilot lights, tap held for a slow 15–20 seconds before release.
Step 3: If It’s New or Just Had a Cylinder Change, Keep Trying
Air in the inlet pipe stops ignition, and the manual’s advice is simply to repeat the sequence until the propane gets through. Three or four patient cycles is normal after a cylinder swap.
Step 4: Check the Water Level
A wet unit needs its bath. If holding performance is the complaint, confirm the tank is filled to just below the pans and hasn’t quietly boiled down during service.
Step 5: Check the Knob Position
Maximum flame is at the 90 position — either side of it reduces the heat. A knob nudged during a wipe-down is a classic slow-bain-marie cause.
Fault: It Won’t Ignite at All
The manual’s fault table gives three causes: no propane supply or wrong pressure, a damaged control valve, or an ignition electrode that has loosened and shifted. The first is yours to check (Step 1 above). The other two are engineer replacements — and if a leak-test or pressure check is needed, that’s engineer work too. If the spark is clicking but nothing lights after repeated cycles and a known-good cylinder, stop and book the visit.
Fault: The Flame Dies as Soon as You Release the Tap
First, be honest about the hold: 15–20 seconds, tap fully in, every time — releasing early is the single most common cause and it isn’t a fault. If a proper hold still won’t keep it lit, the manual points at the fire detector (thermocouple) having dislocated or its lead having dropped, poor ventilation starving the flame of oxygen, or low propane pressure. The thermocouple adjustment is explicitly an engineer’s job; ventilation you can fix by clearing the vents and the 100 mm side / 350 mm rear clearances.
Fault: It Lights but the Water Never Gets Properly Hot
Work through the cheap causes first: knob off the 90 position, too much cold water added at once, lids off letting heat escape, or a draught through the hatch stealing the burner’s output. Then consider limescale — a scaled tank base insulates the water from the 3.3 kW burner underneath, and the fix is the descale routine in our LPG bain marie cleaning guide. If none of those move the needle, low propane pressure is on the manual’s list — engineer.
Fault: It Cuts Out Mid-Service
A flame failure device doing its job. Something killed the flame — a gust through the serving hatch, a knocked tap, a cylinder running empty and its pressure sagging, or blocked combustion air. Check cylinder weight and vents, shelter the unit from direct draughts, and relight with the full hold. Repeated unexplained cut-outs with a full cylinder and clear vents mean the engineer checks pressure and the thermocouple.
Fault: You Can Smell Propane
Close the cylinder valve now. No relighting, no sniffing around with a lighter, no service until it’s found. A soapy-water check on the joints is as far as an owner goes — anything that bubbles, and anything you can’t find, goes straight to a Gas Safe registered engineer. Leaks are the one fault with no DIY column at all.
Quick Fault-Finder
| Symptom | Most likely cause | You or engineer? |
|---|---|---|
| No spark, no light | Ignition electrode loose or shifted | Engineer |
| Spark but no ignition | Cylinder empty/closed, air in pipe after cylinder change | You — check supply, repeat sequence |
| New unit won’t light first time | Air in the inlet pipe | You — repeat until purged |
| Dies on tap release | Hold too short; thermocouple shifted | You (hold 15–20 s) → engineer |
| Water not hot enough | Knob off 90 max, water level, lids off, limescale | You |
| Cuts out mid-service | Draughts, cylinder low, vents blocked | You → engineer if repeated |
| Propane smell | Leak at a joint or hose | Engineer — close cylinder valve first |
| Weak flame everywhere | Low pressure, wrong regulator | Engineer |
Spares: What Fails and What It’s Called
Everything serviceable on these units is a single standard part — thermocouple, ignition electrode and piezo ignitor, 0.88 mm propane injector, propane control valve and knob, burner, drain valve. The 4-pot and 6-pot share the same burner set, so parts are common across the range. Route spares through MobCater as your retailer with your model name and we’ll match them — the units themselves are on the bain marie category page, with the Infernus LPG 4-pot bain marie from £399 if a replacement works out cheaper than a repair on an older unit.
When to Stop and Call the Engineer
Any propane smell. Any fault that survives the safe first checks. Anything needing a tool. The weekly routine in our LPG bain marie maintenance guide exists precisely so these calls are rare — and a unit that was commissioned properly per our LPG bain marie setup guide mostly never makes them. Unauthorised repairs invalidate the warranty, so the moment a fault is real, professional hands are also the cheapest hands.
Frequently Asked Questions
Why won’t my LPG bain marie light?
Check the supply first: cylinder valve open, propane in the cylinder, regulator seated, hose unkinked. Then rerun the full sequence — tap in, anti-clockwise, ignitor pressed until the pilot lights, 15–20 second hold. After a cylinder change, repeat several times to purge air from the pipe. If it still won’t light, the electrode or valve needs an engineer.
Why does the flame go out when I let go of the knob?
Nine times out of ten, the hold was too short — the thermocouple needs 15–20 seconds in the flame before it will hold the propane valve open. If a full, patient hold still fails, the manual points to a dislocated fire detector or dropped lead, which is an engineer adjustment, or to poor ventilation and low pressure.
Why is my bain marie not keeping food hot enough?
Usually one of: the knob sitting off its 90 maximum position, the water bath run low, lids left off pans, cold draughts through the hatch, or limescale insulating the tank base from the burner. All five are owner fixes. Food should hold at 63°C or above — if it can’t after those checks, have the engineer confirm propane pressure.
Why does my new bain marie fail to light the first few times?
Air in the inlet pipe. The manual calls this out for first use: there’s air between the cylinder and the burner, and ignition fails until it’s pushed through. Repeat the lighting sequence — it typically clears within a handful of cycles. The same thing happens in miniature after every cylinder change, so be patient before assuming a fault.
What do I do if I smell propane near the bain marie?
Close the cylinder valve immediately and take the unit out of service. Don’t relight, and don’t hunt for the leak with anything but soapy water on the joints. Any bubbling — or any smell you can’t trace — goes to a Gas Safe registered engineer before the next service. Propane leaks sit outside owner troubleshooting entirely.
Can I fix a bain marie thermocouple myself?
No. Adjusting or replacing the thermocouple means working around the burner and propane valve, which the manual reserves for professional repair — and unauthorised work invalidates the warranty. What you can do is diagnose it: a flame that dies on release despite a proper 15–20 second hold is the classic thermocouple signature to report.
Why does my bain marie keep cutting out on windy days?
Draughts. A gust through the serving hatch can snuff the burner, and the flame failure device then cuts the propane — exactly as designed. Reposition the unit out of the direct draught line, keep the rear and side clearances open for combustion air, and relight with the full hold. Persistent cut-outs on still days need the engineer.
Is it worth repairing an old LPG bain marie?
Compare the quote with replacement cost: the Infernus LPG 4-pot starts from £399 with pans, lids and tap, and the 6-pot from £499. An engineer visit plus parts on a tired unit can approach half that. One failed thermocouple on a young unit is worth fixing; multiple faults on an old one usually aren’t.