Thursday, July 22, 2010

Replacing a gas oven ignitor

My new house has a Thermador range with gas burners and gas oven. I've used it a couple times since moving into the house, but it has a strange problem. When using the oven to bake something, the flames will ignite, then sputter and flicker as the oven comes up to temperature. It seems to bake okay, but the noise from the flames doesn't sound normal. I checked the oven's manual to see if the thermostat has some sort of proportional control so that it tapers off the gas valve as the oven approaches the set temperature. It does not. The flames are supposed to ignite fully, then extinguish altogether.

I started reading about oven problems on the internet, and found a classic problem of searching for information with search engines: there are too many ways to describe a problem. I found people with gas ovens who saw flames that:

flickered
sputtered
fluttered
hiccuped
wavered
pulsed
pulsated
intermittently burned
burped
etc.

Anyway, it seems the root cause of any sort of flame problem is almost certainly the ignitor. This oven has a "hot surface ignitor", which is basically just a heating element that is positioned close to the burner. When the heating element is activated, it becomes hot enough to ignite the gas mixture coming out of the burner. Once the flame is ignited, the heat from the flame will keep the ignitor yellow-hot. As a safety feature, the oven is designed to only allow the gas valve to open when the ignitor is yellow-hot. If the ignitor cools down, the flame must have gone out, and the gas should be shut off. The oven determines the temperature of the ignitor by passing current through it. As the device heats up, it's resistance lowers and enough current flows to activate the gas valve. If the resistance becomes too high (because the ignitor cools down), the gas valve is shut. Ignitors apparently wear out just like light bulb filaments, and eventually their resistance slowly increases over years of use. Eventually, the resistance rises high enough so that the gas valve is just at the cusp of being activated. As the ignitor's resistance fluctuates just around the point where the valve is being switched, the flames will sputter and the oven will not heat as quickly as it should. As directed by troubleshooting guides on the 'net, I put an ammeter in line with the ignitor while the oven was running: 2.9A. It should be 3.2 to 3.6A.

I searched for genuine Thermador replacement parts, since I wanted to keep this oven in original condition. The Thermador website seems to require a registration just to browse for parts, and did not seem very end-user friendly. Forget that! I found some aftermarket ignitors sold by online appliance repair sites for about $80. Then, I found a general fits-all flat-style ignitor for $40. Then, I checked eBay and found a general flat ignitor for $13.50 plus $4 shipping. I figured that I would try it since it was so much cheaper than the rest it would be worth the gamble.
The new ignitor is below the old ignitor in this photo. They are very similar. The new part has two mounting wings, while the original had only one. The length of the stainless steel cage is identical, and the ceramic insulator is a little shorter on the new part.

I installed the new ignitor and the oven works perfectly. The gas snaps on, the flames are steady, then the flames snap off when the thermostat opens. Great!


Here's a shot of the ignitor near the burner tube.

23 comments:

  1. Thanks!

    I have a Thermador Gas Oven just like that too and the part is about $95! Here is the link to the part:
    http://www.repairclinic.com/PartDetail/Hot-Surface-Glow-Bar-Igniter/1013977

    My question is: any generic flat-type igniter works?
    Do you have any particular Part Number that you recommends?

    Thanks!

    Cam
    cnn90@netzero.net

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  2. Anon, the "flat-type" ignitors are all very similar and essentially interchangeable. I would recommend getting a cheap one off ebay since I think they are all made in the same factory and the big manufacturers just add a huge mark-up to the price. Good luck!

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  3. I thought the current draw is different for different models.
    Do you still keep the box so I can get the exact part from you? I'd rather use something that you know works!

    Cam

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  4. Anon, I don't have the packaging anymore, but I believe eBay item# 130462958049 is of the same type. Good luck.

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  5. Thanks!

    Cam
    Omaha Nebraska

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  6. You installed this generic Ignitor in July 2010, is it still working 6 months later?

    Cam
    Omaha NE

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  7. Thanks!!!
    I already ordered the Thermador part, so it is kind of late to return it but I now know what to do the next time!!!

    Thanks!

    Cam

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  8. Thank you to Ben Krasnow for this info. I’d like to write a short DIY (hope this is OK with the owner of this blog!) for those who want to replace the Ignitor. If you are worried about the difficulty, fear not. It is very very easy! I made some mistake and learn it the hard way (because I could not find any DIY on the web!), so I write to help others.

    Thermador Gas Oven Ignitor Replacement:

    Search the internet to understand how the Gas Oven Ignitor (yes, Ignitor, not Igniter) works. Basically it allows current to flow through to heat it up, once it draws certain current that satisfies the “computer”, the gas valve is opened and the burner is fired up.

    OEM is Bosch #415504, I paid $95 for this via Repairclinic.com. However. Per Ben Krasnow, one can use the generic flat-type Ignitor such as Frigidaire GE 5303935066 or WB2X9998 ($15 on ebay as of Dec 2010). So next time I will use WB2X9998, no need to spend $95!

    1. Wear work gloves. The only tool you need is Phillips #2 screw driver. Turn oven gas knob to OFF position. No need to disconnect electricity for this procedure.

    2. Remove all cooking racks from oven.

    3. Remove door (search for Thermador procedure). Basically locking clip on the hinges and door comes out. Set it aside.

    4. On the bottom facade, there are 2 metals tabs that hold the bottom oven tray in place. Loosen (do not remove) these screws and remove the 2 tabs. The bottom oven tray will not slide out as is, read on.

    5. On each side, there are 4 clips that hold the side rack. Remove only the bottom outer clips.

    6. Now slide the bottom tray out and set it aside. Look down and you will see the 2 screws holding the Ignitor. Note the factory wiring, upper wire of Ignitor goes to Blue wire in the Oven. Personally I do not think polarity matters here (I may be wrong) but you may as well do the exact same thing as factory!

    7. Replacing the Ignitor is a straightforward procedure. Reconnect the wiring. Do not re-install the bottom oven tray yet! Turn gas knob on to about 250-300F to test-drive. The Ignitor will glow red hot and in about 15 seconds or so, the gas will flow and the burner is on. Now turn gas knob OFF and re-install everything.

    That is all boys and girls! Thank you to this blog owner again!!!

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    Replies
    1. My husband replaced our igniter, turned oven on and it worked great. Then we had a "pop" sound and the brand new igniter was blown out. Any thoughts as to what went wrong?

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  9. Further to my DIY above, I forgot to mention I have the 48-inch professional model, basically similar to this blog ownner's 36-inch model.
    My model is PRG486GDUS.

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  10. My wife loves me again and by following Bens instructions our Thrmador PRG 486GDUS oven is back in business for a total of 30 minutes of easy labor and less than $20.00 in parts.

    Thank you!

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  11. Thanks, I am going to use the same method on my old hotpoint, to get a bit more life out of it

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  12. Thank you! We have had the sputter problem with our Thermador (same model) for a while now and this has hopefully avoided some high repair bills. Now to search for the ignitor and I will report back when all is finished.

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  13. Just bought one from ebay for $18 total including expedited shipping!

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  14. SUCCESS!! Thank you all for the info here. The $18 part arrived on time (and even included ceramic splicers for the wires!), I followed the instructions above and it now works like a charm! I was able to eliminate the step of taking off the oven door by accessing the screws that hold the above mentioned clamps by partially opening the oven door which gives enough room to remove the two phillips screws.

    My wife just said "listen to that lovely oven ... it even looks better now."

    Thanks!

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  15. Thank you to all the above information. I too moved into a house with this oven. It worked for a short time. I am fairly technical(HVAC Technician)and work on almost anything. Instead of taking the easy way (going to this site for information), I checked gas piping, pressure, gas valve, wiring, and even cleaned the burner. My wife and children have been annoyed by the lack of heat, odor, and noise of this oven for almost a year. I am on the way to an appliance store to purchase new ignitor as we are hosting a holiday party this evening and i can't wait to have one shipped. I am happy to pay the price as this has been a huge headache.
    My Amp reading is 2.7
    Thank you to all....

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  16. Hi Ben,

    I have the exact same oven and while I was turning on the rr range, I turned it past the clicking sound to light the oven and it got stuck. I forced it and it broke the little tab and now it will not trigger the ignitor. How do I replace just that part?

    Thank you.

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  17. I have the 48 thermador, when I turn on my oven it makes it normal noises, but does not heat and the kitchen smells like gas. Could this still be an ignitor? And also, it is the left side smaller oven that is doing this. Would I still follow the above directions that were posted to replace it? Many thanks!!!

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  18. Hii there!!!! I was wondering if you can provide me with the model #of this range I need to order one of the burner cap to get the right one...its been really difficult to find this model online my came without the model # it was a hand me down >>>please help

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  19. Hi Ben i have 48" Thermadore range and my two left burners that are simmer burners don't come on no spark no gas can you give me some advice what it can be. One time the ignitor got stock i turn off the power reset and from that date nothing happens on the two burners.
    Thank you for your time please reply.

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  20. Hello. Wanted to thank you for the great advice. Followed the steps and everything worked great after about 20 minutes and $20. I have the same problem with my broiler. It does not ignite. Could it be the igniter as well. If so, is it the same part nunber as the oven Ignitor? Please advise. Thank you again.

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  21. I had the same problem with my DCS, still trying to figure out this problem of having the tip of the igniter blown out after a few minutes. There was a factory notice regarding the spacing of the igniter tip to the cage that should be around 1 1/4" away from the end. This could be my problem since my replacement igniter was positioned around 1/2" from the end.

    I will try this as soon but had invested up to 3 igniters doing this experiment. First one was the stock DCS, 2nd one was oem with the same Amp rating and rectangular, 3rd one was the made by Whirlpool. All three have their tips blown up.

    So I will order one last one, 4th one, and try the distance suggested by DCS on their service amended document. Funny the original one that failed after 5 years was positioned almost less than 1/2" though..

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