Gas ranges use one of two types of ignition systems for the oven: pilot flame ignition or hot surface. You can read about each kind and how they work in this scroll from the Appliantology scriptures. Here’s an excerpt:

Within the the world of pilot ignition ovens, two types of pilot flame systems are used:

1. the pilot flame is either always on (called a “standing pilot”) or

2. a spark lights up the pilot flame when you turn on the oven (called a “spark-assisted pilot”).

Today, I’m gonna ‘splain how to replace the thermostat in the first type of pilot ignition oven listed above, the standing pilot ignition.

Lots of these old gas ranges are still out there in use today. I actually prefer these ranges to the newfangled electronified junk they’re making these days. The other distinguishing characteristic of this type of range is that it requires zero electricity to operate. No electrical outlet is required because there’s nothing electric on this range. That makes this type of range a popular choice for homes (and camps) which aren’t connected to the power grid. In fact, the pictures in this article were taken during a repair I did for some friends of ours in Vermont who live off-grid.

This article deals with replacing the thermostat in a standing pilot range. One of the symptoms that the thermostat is bad is that the oven won’t fire up but the stove burners still work. So, does this mean that the thermostat is the only thing that can cause the oven to quit firing up? Nyet, tovarish. You may have a bad gas valve or a fouled pilot assembly. So, how do you verify that the thermostat is the problem? I refer you, once again, to my timeless tome on this topic. Here’s another excerpt from that seminal work:

But when you turn on the oven or the thermostat calls for heat, the pilot flame gets bigger and jumps down so it can heat up the thermocouple bulb. This extra gas to increase the pilot flame size comes from the thermostat. This is important to know because it leads to a couple of fine diagnostic points:

• If the pilot flame jumps upwards or just gets bigger, but doesn’t shoot down, then you need to replace the pilot assembly.
• If the pilot flame size does not increase or jump down when turning on the oven thermostat, then the problem is the thermostat not sending enough gas to the pilot assembly. It’s also possible that the pilot gas supply tube has a hole in it somewhere.

Now, slowly re-read the pearls above several dozen times and savor them like fine saké. It helps to also burn incense and chant “Fixitnow.com Samurai Appliance Repair Man” at least 100 times while meditating on this arcane wisdom.

Once you’re posilootely, absotively certain that the thermostat is the bad actor here, then you may proceed with the pictorial guide that tip-toes you ever-so-gently through the tulips of this repair. And you remember the deal with thumbnail pics, da? That’s right, grasshoppah: you gotta click ’em to see the larger picture with the enlightening annotations.

And if you need to buy a new thermostat for your range, type your model number into the parts search box below and you you can buy it right there. It may give you a warm, fuzzy feeling in your navel to know that when you purchase parts through the links at my website and repair forum, it lets me write how-to articles like this one and save you wads of cash on service calls. Domo!

OK, when you’re ready, grab ‘hold of those two large lumps at the base of your spine and let’s romp…

On this range, the thermostat is located in the middle of the control panel. You can access it by removing the grills and lifting the hood, as shown here.

The thermostat temperature sensing bulb is connected to the thermostat via a copper capillary tube. This tube is bonded with the thermostat body at the factory and pressure charged with a gas that expands in response to the temperature. OK, you can uncross your eyes now ‘cuz that’s about as techie as I’m gonna git in the article. The take-away point is that you cannot replace the thermostat separately from the sensing bulb and the new thermostat comes with a factory-fitted sensing bulb.

Notice how the thermostat capillary tube is routed through the top of the range and into the oven and the bulb is mounted on the side of the range. You’ll copy this when you install the new one.

When working on an electric appliance, the first thing you do is unplug it before disassembling it. Similarly, when working on a gas appliance, you need to shut off the gas supply before taking it apart. In a properly installed gas range, the shutoff valve is located behind the range, as shown here. Note that the gas supply line here is copper. This is an older installation where this was the norm. Nowadays, the preferred practice is to use steel flex tube.

Shown here I’m starting the disassembly. The burners are removed and the two aluminum gas tubes are unscrewed from the back of the thermostat body.

To remove the thermostat body from the gas manifold, you’ll need to remove its mounting bolts. In this case, the mounting bolts are located underneath the thermostat. A piece of gasket material between the thermostat body and the manifold tube creates a gas-tight fit. Remember: any connection that passes gas () must be leak-checked when you’re finished.

Here’s the manifold with the old thermostat removed. The gasket material that I mentioned above is stuck to the underside of the old thermostat. The new thermostat kits usually come with a new gasket. That’s about it for the thermostat.

While we have this beast torn apart, let’s feast our bloodshot squinties on the gas valve as an enriching excercise. Here it be. Notice that it has its very own capillary tube and bulb. Wassup wit dat, yo? That’s the flame sensing bulb. It’s a safety feature that prevents the gas valve from opening (and letting gas through) if there’s no flame present. In other words, that bulb has to sense a flame before the gas valve can open. Does this sound like diagnostically useful information? Ya sure, ya betcha! Tuck that away and ponder it during your next morning constitutional.

And here’s a closeup of the pilot assembly itself. This can be another source of problems, as mentioned in my prolegomena comments.

On the back side of the pilot assembly is a plug with a small, precision drilled hole in the middle of it. If this hole gets dirty or partially clogged, which it will on occasion, then the pilot flame will not put out enough heat to open the gas valve.

If the pilot assembly seems to be in good shape otherwise, you can simply clean out this orifice with isopropyl alcohol and compressed air (about 50 psig will do it). Use an air nozzle with a rubber tip so can get a good seal when you squirt compressed air through it.

OTOH, if the pilot assembly looks too boogared up to use any longer, then just replace it.

Here’s the pilot assembly reinstalled and re-connected to its gas supply tube.

Here I’m checking my work by firing up the oven to make sure it fires the burner tube. This is an exciting action shot showing the pilot assembly in the ready position, just waiting for the oven thermostat to be turned on.

Needless to say, we had normal ignition and all systems were go. The Samurai whupped-up on another insolent appliance and restored its design function. Now, go and do likewise.

To learn more about your range/stove/oven, or to order parts, click here.

If your gas oven isn’t firing up, start your diagnosis by checking the ignitor for the proper current draw. “Uh, do what?” you ax, with glazed eyes. Don’t be intimidated by techie-sounding procedures. This is simple stuff– if you can fog a mirror, you can measure current draw. This article explains how to make simple electrical measurements and this one explains what you’re looking for in the gas oven ignitor.

Once you’ve proven that the ignitor is drawing insufficient current (and, therefore, is the correct part to replace to fix the problem), use this handy pictorial guide to hepya change it out.

The wiring for most range ignitors is accessed underneath the oven by removing the pots drawer, as shown here. Why do you need to access the wiring? Two reasons: 1) so you can measure the current draw and 2) it’s part of replacing the ignitor since the new one has to be wired in the same way as the existing one. Take note of where the wires go. The ignitor wires are not polarity-sensitive so don’t worry about “reversing” them.

In this particular range (a Maytag), I had to remove a covering panel to expose all the wires.

Here, I have my clamp-on ammeter on one of the ignitor wires to make a current draw measurement. You can see the closeup of the meter in the next pic.

You can see the current draw reading is 2.4 amps. For a square ignitor, such as this one (you’ll see it in a subsequent picture), the minimum acceptable current draw is 3.4 amps, well above what I’m measuring here. Obviously, in order to make this measurement, the oven has to be turned on and the ignitor getting voltage. This is a LIVE test, meaning there’s live voltage on the circuit. Fire in the hole! Fry yo ace if’n you ain’t careful, Hoss, so… BE CAREFUL!

On some ranges, you’ll need to remove the back panel to get to wiring for one or both ignitors (there’s one each for bake and broil). Yes, this means the range needs to be pulled out from the wall. In the case of a wall oven where the freakin’ engineers didn’t bother to make it service-friendly, you’ll need to remove the entire wall oven from the cavity. If this is the case with yours, you’ll quickly understand why I abhor wall ovens.

Here’s a typical bake ignitor. Note that this one is square. Some ranges, such as older Whirlpools and GEs, use a round ignitor. These two types of ignitors have different current draw specs and are made to be used with different types of valves. This means they are not interchangeable. So, if your range uses the square ignitors, you can only replace it with another square ignitor. The brand doesn’t matter since, by convention, all square ignitors have the same current draw and all round ignitors have the same current draw. For replacement square ignitors, I find that the Maytag universal square ignitor kit is the most cost-effective and reliable. I use this kit in all brands that require a square ignitor.

Note the finesse with which the Master handles his ¼” nut driver. It’s such beautiful poetry in motion that it makes me all verklempt. Or maybe it’s just allergies…

Sometimes, the head breaks off one of the ignitor retaining screws or, worse yet, the retaining screws are phillips screws and they wallow out on you. That’s what we call a Plot Complication (PC). A PC can be any event that results in the failure of the voluntary nervous system to contain a spontaneous convulsion of the autonomic nervous system as it spews voluminous streams of choice adult language, causing any casual observers present to wet themselves uncontrollably.

I can usually work the screw loose using my little channel lock pliers on the threaded of the screw. I’ll then replace the screw with a slightly bigger diameter machine screw with a pointed end and course threads so it cuts itself into the bracket. It ain’t gotta be perfect or purdy, all it’s gotta do it securely hold the ignitor in position.

Lots of times, you’ll need to remove the bake burner tube to allow enough room so you can run the wires for the new ignitor. You’ll usually find two screws securing the burner tube: one in back and…

…one in front.

Here’s the bottom of the oven, with the bottom pan, flame spreader, and burner tube all removed so we have unencumbered access to the bake ignitor wires.

On this range, I also removed the broil burner tube and the broil ignitor is left dangling, just itching to be replaced.

Again, on this particular range, and maybe in the one you’re working on, you’ll have to remove the back panel behind the range. Shown here is the wire harness connector for the broil ignitor. so you just need to connect the new ignitor wires to this harness connector– no need to go all the way back down to the gas valve, like in the bake connector.

So, there you be, Buddy-ree. Easy as pie and 1-2-3. If’n you need parts for your range, come buy ’em from me. Merci!

To learn more about your range/stove/oven, or to order parts, click here.

Dave wrote:

My maytag gas oven is taking longer to pre-heat. What do I check?

You need a new ignitor, such as the one shown here in the thumbhail pic. Click it to git it, install it and you’re good to go. Slam dunk.

Some background reading, if you want to know more:

Troubleshooting a Gas Oven That Won’t Fire Up

Making Basic Electrical Measurements

To learn more about your range/stove/oven, or to order parts, click here.