Gas Oven 'Glowbar' Igniters
How they work, how to replace them
Most gas oven systems today are ‘electronic ignition’, and use
a ‘glowbar’ type ignitor electrically in series with an oven
valve.
Electrical current passing through the ignitor operates a small
heater that ‘warps’ an internal piece of bimetal to open the gas
valve. As long as the burner flame continues to heat the ignitor, its
electrical resistance remains low enough to keep the valve turned on.
If, for any reason, the flame is extinguished, the igniter's
resistance increases and the valve turns off the gas to the burner.
While the valves are very reliable, the igniters have become the
most common parts failure on these systems. Which is to be
expected, I guess; they’re doing their job in a gas flame!
Igniters come in two basic types, ‘flat’ and ‘round’, seen
below, and they can’t be interchanged.
Each type operates at a particular amperage
level, and is matched to the type gas valve it operates. The stainless
steel ‘cages’ that protect them usually correspond to their actual
shape, which helps you figure out which one yours uses. And to
make it even easier, there’s pretty much only One round one that
fits them all. Flat ones vary only in the length of the ceramic
block to which they’re mounted. Electrically they’re nearly all the
same.
While it’s possible to diagnose one of these systems using an
ammeter, it usually isn’t necessary. Since I try to keep life simple,
and since these igniters have really dropped in price the last few
years, it’s pretty easy to figure out what’s up with your cold oven.
If your oven doesn’t light, but you see the ignitor glowing, it will
most likely be glowing a very dull red and not drawing enough
current to operate the valve. Or, in some cases, it will operate the valve very slightly and you’ll smell some gas odor. Neither case is desirable or acceptable!
Watch a clock or stopwatch. If it takes more than 2 minutes to light, you’ll want to replace the ignitor; it’s the culprit in 90%
of these. And this is the best way for you to diagnose your ignition system! In most cases, that’s all there is to it. You don’t even
have to worry about wire polarity on the new ignitor – they can
be wired either way. Just be sure it’s wired like the old one, and
not connected to 120V directly, or it will burn out.
Ignitor and
valve must be in series with each other, or you’ll burn out one or
both, fast!
If you’ve replaced the ignitor and it glows but the oven still doesn’t
light, it’s time for a new valve. They’re pricier, but I usually
recommend doing this once in a range’s life if necessary. Still
much
cheaper than a new range.
If there’s no ‘glow’ at all, take a close look at the ignitor, and
you’ll
often see a crack, or it may even be obvious that it’s broken apart.
You can use an ohmmeter to test for continuity if no cracks are
visible.
Just be sure to power the range down. In some models, one side of
the oven valve is always ‘hot’ with respect to ground, like some
electric
range bake element terminals.
New igniters ship with two ceramic wire nuts, and you simply connect
the new part’s wires to the originals, using the original plug if
yours
has one.
A bit of hi-temp. grease on the mounting screws will be a big help if
you have to repeat this job in the future. These screws are subject to
very high heating, and can ‘freeze’ into their threads so tightly
you’d
like to blast to get them out sometimes!
Copyright 2003 www.DavesRepair.com
This article may be reprinted and distributed freely only
in its entirety, including this message.
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