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Fixing Commercial Fryers [Video]

With almost 300 comments on our Repairing Commercial Fryers post, we figured it was time to get a video out there to better illustrate how easy it can be to fix a fryer yourself.  In this video, Chris Tavano, walks you through calibrating the thermostat, bypassing the hi-limit, taking out the thermopile, taking out the combination safety gas valve, and other troubleshooting tips for commercial fryers.  Please note, before fixing any kitchen equipment, you should ensure the power and/or gas is off first (in the example below, you’ll calibrate the thermostat before turning off power and gas).

For more information, please see our previous post on how to fix commercial fryers.


Hello, welcome to Tundra Restaurant Supply.  I’m Chris Tavano and I’m here to troubleshoot some fryer maintenance today.  Common problems we tend to see are thermostat controls and calibration; in other words, your pilot light won’t stay lit, your burner won’t ignite, your oil is too hot or is too cold.  A lot of common problems associated with that are the gas burner safety valve, as well as, the hi-limit control and thermopile [Chris said thermopiler, but it is indeed formally called a thermopile].  Today, we will be using our Frymaster MJ35 for our example maintenance.

Calibrating the Thermostat: Checking the Oil Temperature Against the Fryers Thermostat

Alright, so first thing we’re going to talk about is the thermostat and how to calibrate the thermostat to help calculate exactly what the problem is.  So, a lot of times you’ll have your thermostat, and your hi-limit shutoff is around 450⁰.

So, what you want to do is set your thermostat to 350⁰, get a thermometer and put it in the oil basin itself, and you want to make sure that, that comes up to the temperature of 350⁰. At the same time, when that temperature has reached on the thermometer, you’re going to lower your thermostat down to about 250⁰ until it clicks off.  And then you’re going to turn it slightly up, and let the oil cool down.  And when that valve kicks back on for the fire, you’re going to make sure that, that temperature on your thermostat is also what’s reading in the thermometer that’s sitting in the oil.


Once you’ve identified the problem of your thermostat being off from the actual fryer oil temperature, the first place to look is your hi-limit switch.  And what the hi-limit does is a safety precaution saying that it’s going to turn off your fryer at exactly 450⁰, and never go higher than that. 

What we’re going to do in here is, you take your two-wires that go to your hi-limit switch, and we’re just going to unscrew them, and switch them in place to bypass that [we’re bypassing the hi-limit switch here].  We’re going to take the one that gives us the source to the thermopile.  This one is our actual limit, and we’re just going to bypass it and go instead to the thermopile.  Really, all you need to do is get the one that connects back to the thermopile so we have a constant source again of that flame.


Alright, if you found out that your hi-limit switch is not the problem, the next place to look is your thermopile.  A thermopile converts your thermal energy into electrical energy.  It is the source of your thermostat.

Back in this corner here we have our pilot light and our thermopile. The thermopile is the rod that is connected to this snaked wire.  Takeout [usually unscrew] the probe itself and there’s your thermopile. [The thermopile needs to be checked for corrosion or broken wires and replaced if damaged.]

Combination Gas Safety Valve

If you’ve found out that the hi-limit and thermopile are not the culprit of your thermostat controls, the next place to look is the combination safety gas valve.  That is not an easy thing to replace, it is not a quick thing to replace, and it’s not necessarily cheap, but it is something that needs to be done, and it’s much better than buying a whole new fryer itself.

If you look at this particular model, the whole unit of the [combination] safety gas valve itself cannot be removed from right here, so what you’re going to do is find your closest joints.  Unscrew those, and your other one right here.  And your actually going to pull out the entire device with all of the component pipes associated with it.  Once you pull that out, you can replace these pipes [take the pipes off of the combination safety gas valve] so that way you have the actual safety gas valve itself.  And then you can get that replaced, you can hook it back up to your previous pipes, and then again, you can screw that back on to the actual gas lines themselves.


Alright, so your last troubleshooting tip would be the thermostat itself.  If you find that you’ve gone through all of that stuff, and your pilot light is staying lit, but however, you aren’t holding temperature through what you had calibrated earlier, and it’s not being consistent, odds are the thermostat itself is bad and needs to be replaced.

Other Common Problems

Alright, so other common problems to try and troubleshoot with your fryer tend to be [small] explosions, it’s too hot or metal fatigue.  A lot of times, you’ve got to check the basin of your fryer itself, and make sure that there are no thin spots, worn out spots or any holes within the basin.  If that exists, you have to get a new fryer.

Other places you need to look are in your exhaust manifolds and in the flume burners themselves.  A lot of times they get caked with grease and excess runoff, and over time, those just don’t get cleaned out the same way that the oil basin itself gets cleaned.  So you’re going to want to check those on a monthly or quarterly basis, and try to clean out the soot.  If it’s caked in there, odds are you might need a new fryer as well.

Another common mistake is liquid propane to natural gas conversions.  Those are one-way valves, so to convert from natural gas to liquid propane, there’s one valve for that.  To go from liquid propane to natural gas, there’s a different valve for that.

For more information, please see our previous post on how to fix commercial fryers.

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  1. This is a great how-to video, thank you! I’m always looking for great content and resourceful information for the bar and restaurant owners we support. I pinned it to one of our Pinterest boards geared toward this audience. Thank you!

  2. Hi. I have an Anet deep fryer that has a small flame coming from the top and generates black smoke. What could this be from? It’s a gas fryer and oil is in it so I’m not sure why it flames and smokes

    • Tundra Restaurant Supply

      Robert, where exactly is the flame coming from? Is it burning off carbon, etc. If it has no source it might be bypassing gas somewhere.

      Can you blow out the flame & reignite where it’s coming from?

  3. I have three gas fryers. each say they are set up for propane or lpg gas. two of the fryers were already in the kitchen when i bought the place. The kitchen is hooked up to natural gas though. So how do i know if these fryers have been converted over. Is there anything on the gas valve that states whether it’s for natural or propane?

    • If the conversion was done by a professional, hopefully they would have applied the stickers that are usually supplied with the conversion kits explaining that the unit has been converted. They are typically applied near the model number location or directly on the combo safety valve.

  4. I have just bought an imperial fryer it looks like it hasn’t being used much at all everything looks like new but when it’s lit flames shoot out the chimney . I’ve cleaned the jets and the flute can you help ( basin like new to )

    • Hi Colin,

      Chances are you have one of 2 problems. Either the flue path is still clogged and not getting proper flow or if you already cleared that out the more likely cause would be manifold pressure and orifice sizing. If the unit is not mixing the right ratio of oxygen to fuel it will not burn blue and clean. These adjustments require specific tools and training and should be preformed by a qualified technician.

      – Paul
      Tundra Team

  5. Hello, my cousin owns a pizza shop and has two fryers. One is a four basket and the one with the problem is a two basket, both Natural gas. He was cleaning the larger of the two and managed to spill greasy water all over the smaller and now when it’s turned on, the 4 burners come on as normal but then the orifices light up right after and flames shoot out of the orifices where the primary air normally mixes before traveling down the venture tube of the burner. Also because of this happening there is now a lot of soot on the ports, however they still work like they should (minus the flames at the ports) He had no problems until the other fryer overflowed with greasy water and I am just finishing up my first year of college to become a gas tech and haven’t got to involved with commercial burners yet. I am thinking that there is a blockage of some sort but am confounded that the ports still operate. your opinion would be greatly appreciated as it is March break and wont be able to get my teachers opinion for several days..

    • Hi Jason,

      Airflow could have something to do with your problem. If the flue is blocked it might be pushing the flame back down. Also your burners might not look like it, but if the holes get blocked even just a little it could be restricted by 25% or so. Take out your burners and put them on your char broiler covered with aluminum foil and cook them at full heat for an hour and then put them aside for another hour before you wash them out as they will be 1000+ degrees, but this will burn off every bit of carbon and a bunch of ash should wash out of them. Doing this every 6 months isn’t a bad thing to do. Remember, cleaning often solves a lot of issues in a kitchen.

      – Paul
      Tundra Team

  6. Hello, I have a gas fryer that has a very low blue flame on the pilot which doesnt enable me to light the fryer burners or flutes. We cleaned out all the parts in case there were any clogs but same thing. Any ideas of which part might be faulty.

    • Paul, it sounds like you just need to adjust your pilot up a little. This picture should show you where to remove the cap exposing the adjustment screw underneath.

      – Paul
      Tundra Team

  7. Hello

    I have a almost a year old Pitco deep fryer. It lights up fine but when it reaches its temperature, it shuts down. It will not light up when I try to ignite it again as soon as it goes off, but I wait for 30mins, it ignites properly again. Any idea what might be the issue here.

    • Nick,

      You have to have a high temp thermometer in the oil to really tell what might be going on. It’s possible that the thermostat is letting the unit get too hot and the high limit is doing it’s job and shutting off the unit before it catches on fire, or the high limit is bad and shutting off too early. You had mentioned that you’ve had the unit for less then a year. If that’s true, then the unit is under warranty and you should reach out to the factory with your Model and Serial number and they should take care of it for you.

      – Tundra Team

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