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Kelly
Kelly, Appliance Technician
Category: Appliance
Satisfied Customers: 19129
Experience:  Highly accurate diagnostician with over 30 years experience!
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I have a Kenmore gas range - Model 790.71463703. The cook

Customer Question

I have a Kenmore gas range - Model 790.71463703. The cook top is working fine, but the oven apparently has an incomplete combustion, as it's creating carbon monoxide when we use it (we had the fire dept come out and test the levels - it's definitely coming
from the oven and not the cook top). One thing to note is that we've noticed the face of the control panel on the top has started to melt and become disfigured (image attached). I don't know if that plays in to the problem. We had to replace the control panel
a few years ago because the oven wasn't working, but we did not replace the face of it at the time.
Submitted: 1 year ago.
Category: Appliance
Expert:  Kelly replied 1 year ago.
Hi, welcome to Just Answer. My name is ***** ***** I look forward to helping you! A weak igniter can cause this issue as well as a problem with too much fuel to air ratio. Has the range been converted to LP? Is the oven sooting inside?
Customer: replied 1 year ago.
Nothing has changed on it since we bought it (no conversions or anything). I'm not seeing any sooting.
Expert:  Kelly replied 1 year ago.
Okay, and do you know how the CO was tested? Did they just take a sample from the kitchen area or did they probe the actual oven vent?
Customer: replied 1 year ago.
Both. They had a reading in the kitchen and then took a reading in the oven to determine that was the source. I also have a digital carbon monoxide detector that was reading the same amounts as their sensors.
Customer: replied 1 year ago.
Looking again, and it does appear that shooting has occurred. This is recent because it hasn't been this bad.
Expert:  Kelly replied 1 year ago.
Well, there is no way to measure the oven itself unless they had a combustion analyzer. A CO detector is not able to determine the CO output of an oven. However, if there are no other gas appliances in the kitchen, it may be an issue. Given that the control is getting damaged, too, I suspect the issue lies with the oven vent. The vent is shown as number 36 in the diagram at the link below. Do you have a long brush that you can use to sweep through that vent? CLICK HERE
Customer: replied 1 year ago.
I would think it's fairly easy to determine it was the oven. They turned the stove top and got 0 reading. When the oven turned on, their sensor shot up. There's no doubt it's coming from the oven. There are no other gas appliances nearby. And the fact the stove top didn't set it off would lead one to believe it's not from the gas supply.
Expert:  Kelly replied 1 year ago.
The oven will concentrate CO at the vent, a very small area. That is why you need a combustion air analyzer. It is the same as sticking a CO probe in a water heater vent, of course it will read high, you are reading a direct vent of the CO. But that is really neither here nor there. Like I say, I suspect the issue is with the vent. Are you able to clean that vent with a brush to see if it is clear?
Customer: replied 1 year ago.
Ah...I understand now. Let me look for a brush. Any recommendations? It's kind of an awkward open to get a brush inside.
Customer: replied 1 year ago.
Should I clean from the top of the vent, or go inside the oven and clean from the bottom?
Expert:  Kelly replied 1 year ago.
A condenser brush, like the one below, works great! CLICK HERE
Expert:  Kelly replied 1 year ago.
A long flexible brush from the top will work the best. Those style brushes are available at most any hardware store.
Customer: replied 1 year ago.
Vent is clean. Were you expecting soot or it being clogged?
Expert:  Kelly replied 1 year ago.
Yes, or sometimes food gets dropped down there during spillovers. If you remove the floor of the oven do you can see the burner flame, is it orange or blue with light yellow tipping? Was the original issue just the CO detector going off?
Customer: replied 1 year ago.
Flame looks fine on the bottom.Yes - CO detector went off when my wife opened the oven after baking for an hour. We have a digital reading detector. After I took it outside, reset the detector and got it to zero, I brought it back in the house, and I noticed it was hovering between 30-40 PPM.
Expert:  Kelly replied 1 year ago.
Okay, well if the flame is blue, it is burning correctly. How close is the CO detector to the oven?
Customer: replied 1 year ago.
When it went off, it was on the ceiling about 10 feet away and 6 ft above the oven
Expert:  Kelly replied 1 year ago.
In the kitchen? Has it always been mounted there?
Expert:  Kelly replied 1 year ago.
The excerpt below is from the CPSC site at the link below. CLICK HERE CO alarms should be installed according to the manufacturer's instructions. CPSC recommends that one CO alarm be installed in the hallway outside the bedrooms in each separate sleeping area of the home. CO alarms may be installed into a plug-in receptacle or high on the wall. Hard wired or plug-in CO alarms should have battery backup. Avoid locations that are near heating vents or that can be covered by furniture or draperies. CPSC does not recommend installing CO alarms in kitchens or above fuel-burning appliances.
Customer: replied 1 year ago.
We have an open floor plan. The alarm is detector is battery operated (like a fire alarm).It's technically in the breakfast area of the house. It's been there for 7 years and never gone off. Something is definitely wrong with the oven. I don't think there's anying wrong with the placement of the detector.
Customer: replied 1 year ago.
Here's a picture.
Expert:  Kelly replied 1 year ago.
That is why I asked how long it had been placed there. If the flame is good and nothing has changed regarding the combustion air available to the oven, I suspect the CO detector may be acting up. They have a 5-7 year life, so it will be a good investment to replace it now anyway. I would start there and if the new detector alarms. One thing I have seen , especially in newer, well insulated homes, is if the AC is on or other air handling equipment, it can actually reduce the combustion air from the oven and cause the flame to lift from the burner. It can be very difficult to diagnose because once you open the area to inspect the flame, you introduce more combustion air. If you open that window with the oven on, does it still alarm?
Customer: replied 1 year ago.
I don't understand how it could be anything other than the oven. The firemen came out with very sophisticated sensors and determined it was from the oven. When the oven was off, no CO. When turned back on, it came back.Nothing was different about the night the alarm went off than any other night.
Expert:  Kelly replied 1 year ago.
I totally understand, I am just trying to determine what may be causing it. You say the flame is good and the vent is clear, so it makes no sense. Beyond replacing the range, I am out of ideas. I will place your question back to the list for others to see in case another has an idea. Please do not rate or it will lock your questions and delay any further responses.
Customer: replied 1 year ago.
Thanks for your help.

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