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WFG515S0ES1 Whirlpool oven will not maintain temperature

Eggman317

Premium Member
Joined
Feb 10, 2018
Messages
12
Location
Pittsford, NY
Model Number
WFG515S0ES1
Brand
Whirlpool
Age
1-5 years
Our 14 month old oven heats up to temperature fine, then the burner shuts off (as it should), but it never turns back on to maintain the temperature. If I cancel it and restart it, it turns back on and heats up, but the same problem continues. I checked the temperature sensor, and it reads 1080 Ohms, so it appears to be working, but I read somewhere that it may read correctly at room temperature, but fail at elevated temperatures. It is a fairly inexpensive part, so I could buy one and see if it fixes it, but I thought I'd see if anyone else has a thought before I did that. Any help? Thanks.

I just ran a diagnostic check and no error appeared. I also heated the oven up to temperature, unplugged it and checked the temperature sensor again while the oven was still hot (the sensor connector is accessible in the back). It is now reading a little over 1600 Ohms. Is that what it should read at this elevated temperature?
 
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rickgburton

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If the temperature was around 350*F, that's the correct resistance. Measure the resistance of the bake and broil coils on the oven safety valve. Your meter should indicate 216 ohms for both coils. If one is out, neither one will work.
Safety Valve WPW10602001
MGR7662WB4 Gas Valve.jpg
 

Eggman317

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Messages
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Location
Pittsford, NY
Rick, thank you for the reply. The safety valve is fine. Both are reading 216 Ohms. What else could it be? I'm afraid that it is the control board (the most expensive part to replace). I'm hoping it is something else though. Any other thoughts?
 

rickgburton

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OK, After the oven reaches temperature and shuts off you're saying it never turns back on, correct? Do you hear the igniter spark? After the oven turns off and the temperature drops below the set point check for 120 VAC supply voltage at the DSI board across J1-4 and J1-6. If the voltage is correct check for 8-18 VDC across J1-1 and J1-2.
 

Eggman317

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Messages
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Location
Pittsford, NY
Yes, once it turns off after it reaches temp it never turns back on again, although the display still reads the set temperature. The ignitor does not try to light once it cools down a little. Although last week it did spark and not ignite when we tried to start it from the beginning. That problem seemed to go away and this new problem appeared. At least this is what WAS happening. Interestingly, when I tried to check the voltages right now it is working fine. The oven is igniting and holding temperature correctly. Strange. I'll keep an eye one it. Something must not be right, but maybe it is intermittent. Any thoughts?
 

Eggman317

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Messages
12
Location
Pittsford, NY
OK. I think my oven is possessed. Here I what I'm doing and what the oven is doing:
1. Set the temperature to 450 for dinner. It worked fine (as I posted above).
2. Cancelled, then set it for 350, after it had cooled down to 280 and it heated up to 350, but never kicked back on again.
3. Cancelled and immediately set it to 450. When I pushed start, the display read 385!
4. Cancelled and immediately set it to 325. When I pushed start, the display read 305!
5. Cancelled and immediately set it to 425. When I pushed start, the display read 420! It heated up for a minute, then stopped. It did not kick back on to heat it back up though.
I repeated this at several different temperature and the display always seems to read about 10-20 degrees below the set point I choose.
 

Eggman317

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So, it appears to be heating up way above the set point. I put a thermometer inside to read the actual temperature. I set it to 350 and looked at the thermometer when the display read 350 and the oven shut off. The thermometer read 450. No wonder the fries I baked for dinner got so burned! The oven does actually kick back on to heat it up, but not until the actual oven temperature drops back down to 225 or so, which is several minutes later. It then heated up to I'm not sure if that means the temperature sensor actually is bad? I just checked the resistance when the display said 350, but the oven was at 450 and it read 1140 Ohms.

I checked the terminals you mentioned too. While it was cooling down, I was reading 94 VAC across J1-4 and J1-6 and nothing across J1-1 and J1-2, although I think my probes are too big to contact the ferrules on the ends of the wires.

Sorry, I keep playing and noticing more things. In diagnostic mode it says the temperature is 300 degrees, which matches my thermometer. I cancel and immediately press bake, set the temp to 300 and press start. The oven starts heating up, but the display only reads 200 degrees. It heats up to 300 degrees on the display, but 380 on the thermometer. I cancel and enter diagnostic mode again and the display reads 400 degrees. It cools down to about 200 (by the thermometer), then heats back up.
 
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Eggman317

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I was hoping it was just the temperature sensor, but it was reading the correct resistance (see my first post), so I thought it was working fine. If you think it could still be that, I'll order one and try it out first. If it doesn't help, maybe I can return it and get a control board.
 

rickgburton

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..... the oven was at 450 and it read 1140 Ohms.
That's not the correct resistance. 1140 ohms is barely above room temperature. I posted the RTD sensor temperature chart in post #9.
 

Eggman317

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It was reading 1080 Ohms at room temperature and a little over 1600 Ohms at around 350 (at least the display said 350 when I checked it then). So it matched the chart. I just checked the resistance again though when it was up to temperature. The display read 350, but the thermometer read about 450 and the resistance was around 1790 Ohms. So, maybe that is the problem.
 

rickgburton

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So how good is your thermometer? If you purchase a part from a link on this site and it doesn't fix the problem you can return it for a full refund less shipping.
 

Eggman317

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I'm sure it is not that good. It is just an analog candy thermometer. I was just using it to get a comparative ballpark reading. Since it was reading 100 degrees different there is obviously something amiss. I'll try the sensor and see what happens. I'll let you know.
 

Eggman317

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I received and installed the temperature sensor. The oven still heats up to 100 degrees above the set point initially, then it cools down to 10 degrees below the setpoint, then heats up to 10 degrees above the setpoint. So, it appears to only heat up too much for the initial heat up. I took the new sensor out and put the old one in and it did the exact same thing. I'm thinking it is not the sensor. It may have been doing this before too, but I wasn't being patient and opened the door too much to cool it down faster. Maybe that is why I was getting low temp readings on my thermometer. So, something doesn't seem right still, but it is usable. Would the control board be the problem with it heating too much initially? I know for a fact that it wasn't holding temperature at one point previously, because we cooked dinner and it wasn't even close to being done at the time it was supposed to be and the temperature seemed way too low. It is not doing that now though. ????
 

Eggman317

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Well, I'm back. It was working fine for a while (with the original temperature sensor and control board), but just this week started acting up again. It was doing the same thing again, heating up to 100 degrees above the set point for the initial heat up, but then going to the right temperature after that. So, I bought a new control board, since I had already tried the temp sensor. I swapped them out and it still did the same thing. So, the temperature sensor didn't fix it and the control board didn't fix it. What else could it be? It is definitely getting way too hot initially.
 

rickgburton

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...heating up to 100 degrees above the set point for the initial heat up, but then going to the right temperature after that..........It is definitely getting way too hot initially.
OK I think you're missing something. That's basically how all ranges work. It's normal for the first temperature rise to go past the set point, some models as much as 50°. After that, the temperature usually starts cycling off ±10° of the set temp. Even if the initial temperature rise was 100° over the set point, it shouldn't matter unless you have a recipe with 1-2 minutes cook time. I have a feeling your analog candy thermometer might be giving you erroneous information. You need a DMM that uses a digital thermometer with a fast response time.

...the temperature sensor didn't fix it and the control board didn't fix it. What else could it be?
Here's why I question your candy thermometer. It can't be anything else. The control board uses the information from the oven sensor to control the spark module and oven valve. Where did you get the control board and what is the part number? It's possible you got a bad new control board. That's not uncommon in the appliance world. Measure the resistance of the oven sensor at different temperatures. In the past I've seen oven sensors check good at room temperature but open or short at a higher temperature.
 

Eggman317

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Rick,

Thanks again for the response. I have to admit that I bought the control board used on eBay, since we are moving and didn't want to spend $200+ on a brand new board. It would seem strange that it would have the exact same issue though. I tried to check the resistance of the temperature sensor, but it was acting funny. When I check it with the sensor out I get around 1180 Ohms at room temperature, which is fine. When I try to check it when it is installed and the oven is heating up it jumps from 1 Ohm to 1500-1700 Ohms then immediately to 1900+ Ohms, then back to 1. The probes are fully into the sensor's connectors and it keeps doing this no matter how I fidget with the probes to ensure they are making good contact. It also causes the oven gas to shut off sometimes and stop heating up. I bought a new sensor and the multimeter is doing the same thing. I'm not sure why this would do this. It almost seems like there is a wiring problem somewhere in the oven.
When I check the temperature sensor with it unplugged but still installed (after heating up the oven) it reads correctly (although it matches the candy thermometer readings). This is what I got:
1865 Ohms when the oven said 350 and the candy thermometer read 450
1660 Ohms when the oven said 250 and the candy thermometer read 350
1350 Ohms when the oven said 150 and the candy thermometer read 250

I got similar results with the new and the old temperature sensors. So, I don't think that is the problem. It is either a wiring issue or the control board again. Although, again, what are the chances that both boards are bad and giving me the exact same temperature issue. Thoughts?
 

rickgburton

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Eggman317 said:
... again, what are the chances that both boards are bad and giving me the exact same temperature issue.
With a used board I would say 60/40. There is a lot of appliance places that sell used appliance. They buy a bunch of used appliances from major retailers. It's the ones the major retailer picks up when they deliver a new appliance. They buy all the ones they picked up for about $20 each, junk or not junk. They fix the ones that are fixable and sell them for a profit and strip the parts out of the ones that are not fixable for future use. Most of the time the parts they save are for them. Then came eBay and amazon and they found a new market for used parts. None of the parts are tested when stripped from an appliance. They usually tell you, if it doesn't work they will send you another one.

That's a common part to fail on that model. Most appliances are replaced when the repair costs starts getting close to the price of a new machine. I'm sure there were a lot of people that opt for a new range when the service tech told them the price of the control. The control is the only real expensive part on the machine. The only other reason to replace it is if they were remodeling their kitchen. So a used board either came from someone remodeling or the more likely, a range with a bad control board.

Here's a temperature resistance chart for the RTD sensor:
RTD Sensor.jpg
 
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