Jenn-Air FCG20510 oven fluttering gas modulation

[slantsixdan]

When in bake mode at any reasonably normal baking temperature (say, from 300 to 450), I frequently hear odd fluttering modulation of the gas flow to the burner. Instead of a long burn followed by a shutoff, I get a long burn followed by a series of very short...sort of "Pffp, pffp, pffp, pffp, pffp, pffp, pffp, pffp, pffp" sounds like, as I say, fluttering modulation of gas to the burner. Sometimes these are followed by a long burn, sometimes by silence. Have noticed no especial performance trouble from the oven, no smell of raw gas or anything, and it does reliably light off and heat up, and -- at least according to the temp display on the electronic control panel's readout -- does attain and maintain the temperatures I select.  I will confess I haven't put a real thermometer in the oven to check.

Guru, if you have this service manual and can upload it, I would surely appreciate it.

Thanks in advance, all.

[Budget Appliance Repair]

May have a oven safety valve going bad. The bi-metal may not be snapping open and close with a snap but a slow gradual bend. This would cause a small leakage of gas as the flame is going out and do the pffp,pffp,pffp,thing as the gas is gradually being shutoff instead of an instant off.

You may even have a very, very tiny gas leak when the range is off and just not smell it because it is so small.

You need to take the oven burner off and check for leakage directly at the oriface opening.

Watch the oven burner as you turn it on and see if the when the flame comes on it does so in a very quick manner or if the flame starts out real small and gradually gets to full flame. I would say that if the flame doesn't come to full flame after first coming on in less then a second or two you have gas safety valve going bad.

[That Guy]

Or you could have a weak ignitor. Seeing how this is the famous 12400035 ignitor and knowing how much they love to fail. I would try it first.

[Samurai Appliance Repair Man]

Well, I tried but I can't look up the manual you need with a Canadian model number.  I think Willie's on the right track, though.  I've seen lazy bimetals in gas valves cause this problem as well as marginal ignitor current draw.  A current measurement may provide more insight.  If you have a clmp on amp meter, measure the ignitor current draw and post the results.

[slantsixdan]

Drat. Didn't figure this to be a Canada-specific model...it hasn't got bilingual labelling or anything. Maybe just different regulatory approvals. *shrug* Any suggestion for how to cross the Canadian model to a US model similar enough to make reading the manual worthwhile? It was made between '94 and '96, if I'm not mistaken. And 13 pages' worth of model-applicable parts come up when searching under FCG20510 on repairclinic.com .

No clamp-on ammeter, though I do have a regular series type that'll probably be a great deal more hassle to use in this case, I'm guessing.

[Budget Appliance Repair]

If you don't have clamp-amp meter then check the voltage at the valve with the ignitor glowing and flame burning and see what AC voltage you have directly at the valve.

It should be pretty close to what the amp reading should be. I had never known this before, (always used a clamp-amp meter), tell someone here mentioned it.

You should see an AC voltage of right around 3 volts if the ignitor is ok.

[slantsixdan]

Thanks! Will give that a try.

Now I'm going to have to find a quiet way of asking really ignorant questions like "How do I gain access to the bottom burner and its ignitor & wires?". :shock:

[Trying to help]

The unit was a Jennair made for Sears only unit.  You will not find a Service Manual for it, at least not through normal channels.  Is the unit on LP or Natural gas?  If LP, could just be end of ignition extinction popping.  Kind of like when you turn off your BBQ and start walking away.  You hear a flutter and then a poof or pop.  The hotter it gets, the more pronounced it is.  The model would be comparable to a CRG9800CAB Maytag which I do not believe had a service manual either.  Since they were just similar ranges with the only difference being a fluorescent light, they were just covered under a generic service manual produced at the time. 

[slantsixdan]

Thanks, great info. The unit's burning natural gas, not LP. I thought of the barbecue effect you mention, but:

  1) Didn't know it happens with LP but not NG (why?)

  2) It's definitely not the same effect.

Any idea how I'd get hold of this generic service manual you mention?

Thanks again...

[Trying to help]

I'm traveling today but will be back in office Thursday.  I will see if I have the part number for the manual.  The reason the noise is more prevalent in LP is because of the pressure differential.  It is almost like a flash back or vacuum effect when it kicks off.