Kenmore Pro Elec. Oven Not Heating Up

[bldn10]

This is a 10-year old Kenmore Pro dual fuel freestanding range model no. 790.79523. I don't use the oven much and frankly am not sure if it ever worked correctly. I have checked the voltage and replaced the temp sensor., but:  

in Bake mode it will not heat past around 250*; 

it appears to me that both elements heat but the top one does not get red and water poured on the floor does not quickly boil off;

in Broil mode, the top element gets red hot as it should,;

in Convection Bake mode, the fan comes on but the elements are as in Bake mode.

I'm afraid I need a new control board but before I shell out $188 I'd like others' thoughts. Thanks,

Bill/Memphis

  

[Brian B]

Try to calibrate thermostat by with a little finger button dance. You can find calibration info in user manual, if you dont have it, just go online.

[bldn10]

The calibration feature is to adjust the actual oven temp up or down from what the setting (thermostat) is and is limited to 35*. For example, if you have it set on 400 but the actual temp is 375, that can be adjusted using the calibration. It's not that my elements shut down at too low a temp - they stay on but the temp never gets above 250. The elements do not seem to be getting full voltage in Bake mode.         

[Brian B]

Maybe see if you can get an amp draw from the control to one of those elements that are not red, compare to red one to confirm the control board

[tjweaver84]

Did you check voltage to the range, or did you check the voltage drop across the elements? The tech sheet says bake and broil elements should have voltage applied during bake and during the first temperature rise the convection element should have voltage applied. Looking at the block diagram of the tech sheet you would want to check the following points for drop of 240 vac

P7-P1 (Broil)

P9-P1 (Bake)

P11-P1 (convection)

You could also do current checks of elements. Bake and Convection should have around 10 amps and broil should be around 17.

[bldn10]

Just to the range, TJ, I haven't opened it up yet. Let me ask you this - first, I assume that the elements work like most heaters, A/C compressors, etc. in that they cycle on and off at 100% power? And the board acts simply as an on-off switch, either sending full power or nothing? If so, then how can my top element, which I know is capable of going red, partially heat in Bake mode? [Unless it is cycling so fast that it never goes red.] If we get to the point where it seems highly probable that it is the board, that's all I need to know. Thanks.         

[Budget Appliance Repair]

16 hours ago, bldn10 said:

 [Unless it is cycling so fast that it never goes red.]

That is exactly what happens, almost all the Frigidaire built ranges cycle the broil element on for about 10 seconds of every 1 minute duty cycle, (Bake power turns off when the Broil is power for this 10 second period).  This is for more even preheating of the oven cavity in bake mode.   Once it has reached pre-heat temp some of them only then cycle the bake element on/off to keep the temp stable and don't turn the broil on anymore.

[tjweaver84]

The tech sheet for your model does not state a duty cycle for the elements, but the control will cycle them as needed to preheat and maintain temperature. Looking at tech sheet it looks like your unit uses both bake and broil after it finishes first temperature rise and preheat is finished. For preheat (in both bake and convection) it cycles bake, broil and convection elements and runs convection fan at high speed. Once preheat is finished if in bake it stops the fan and stops using convection element. In convection it should continue to use all 3 elements and shifts fan to low speed after preheat.

The different options (bake, convection etc) should have different duty cycles for the different elements, but while energized you should be able to check by current if they are doing the amount of work they should be doing.  My hypotheses would be that either one of the elements is not putting out the heat it should be (amp test) or the board is not reading the RTD correctly (test sensor resistance as below, stick thermocouple (or thermometer if not thermocouple) in oven and check actual temperature vs what the display shows).

The convection and bake elements have same power rating so should have similar amps (around 10), broil is a higher watt element so should have a higher amp reading (about 17).

Temperature sensor (RTD) for the oven can also have resistance checked at a couple known temperatures (70F should read about 1080ohms and if you have a heatgun you can heat the sensor to ~1000F you should read about 2875 ohms).

If all the elements are testing in spec, the RTD tests in spec and the board is cycling elements correctly it should reach temperature. Also check for loose connections while you are in there. If all connections are good and everything (RTD, elements, set temperature on display) tests in spec then it points to the board not doing it's job.

[bldn10]

Ok, I finally got around to pulling it out and checking the board. What I found is that both elements get 240 v  at some time or other. This thing really does a lot of cycling back and forth between the upper and lower elements. On Bake it starts w/ the lower for <20 secs., then switches to the upper, then neither, then back and forth and so on. But it never reaches the set temp. I'd think the elements would stay on until the set temp is reached, and then alternate to maintain.  Broil works just fine. Convection Bake seems right but is slow to get up to the set temp. [Recall that I just replaced the temp sensor.] I didn't like the way the plug is loose in the socket so I am going to replace the latter. As far as replacing the board, I'm afraid this test was inconclusive. I suppose I should check the lower element. If I can figure out how to get to it.    

[bldn10]

I'm certainly no appliance man nor electrician and my inexpensive digital multimeter may not be accurate but, even so, these results seems anomalous.  Current on the lower Bake element shows .069a, 0.00a on the Conv. Bake, and .098a on Broil. 

Resistance is 23.4, 22.3, and 14.3, respectively.   

[bldn10]

Looks like I lost my audience. I guess I'm just going to go ahead and replace the board.  

[vee8power]

What are the symptoms? No heat?

Sorry, I only read the last 2 posts.

Edited December 14, 2019 by vee8power

[Terry Carmen]

On 12/7/2019 at 11:59 AM, bldn10 said:

I'm certainly no appliance man nor electrician and my inexpensive digital multimeter may not be accurate but, even so, these results seems anomalous.  Current on the lower Bake element shows .069a, 0.00a on the Conv. Bake, and .098a on Broil. 

Resistance is 23.4, 22.3, and 14.3, respectively.   

>  Current on the lower Bake element shows .069a, 0.00a on the Conv. Bake, and .098a on Broil. 

Those are all wrong. The current should be 10 amps or more on the bake element when it's on.

I think you blew up your meter. The inexpensive meters (not clamp on) can't measure more than 10 amps. Some contain a fuse, some just blow up.

As for the oven, check the voltage to the bake element while it's set for bake. If you don't have ~240 volts at the element, check the oven wiring before buying a control board. If you do have 240 volts and it's not getting hot, you need a new element.

Also check your meter. Plug it in to a regular outlet and see if you get 115 volts more or less. Also check the current for a lamp with a 100 watt bulb. It should run about 0.8 amps.

> control board

The elements are actually powered by a separate relay board. You'll need to see if the problem is that the relay board isn't delivering power or that the control board isn't energizing the relay board.

 

Edited December 14, 2019 by Terry Carmen

[bldn10]

Thanks for weighing in, Terry. Forget those current nos. -  I now realize that my DMM does not even read AC Amps, only AC and DC mA and DC amps. I had it on DC10A so those nos. are who knows what. Probably did blow it.

But, yes, I am getting 240 V to all elements. On Bake the oven will not get over 250*, Broil seems to work OK, and Convection Bake will eventually reach set temp but is too slow to use. I have replaced the temp sensor, which appears to have been OK. It seems like the elements just don't stay on long enough.      

[Terry Carmen]

> But, yes, I am getting 240 V to all elements. On Bake the oven will not get over 250*, 

That makes it easy. If the bake element is getting 240 volts at the bake element terminals, and it's not getting really hot, it's bad.

 

Edited December 14, 2019 by Terry Carmen

[bldn10]

I did a little test by unplugging the upper element and then turning it on in Bake. I was able to confirm that the lower (true hidden) element does come on and gets somewhat hot but it seems to be cycling "normally" although the temp is not rising normally. I was thinking that an element either works or it doesn't - it doesn't heat partially if getting full 240V. If that is so, then it would seem that the element is OK but duty cycle is off. FWIW I pulled the plug from the board and checked the resistance of the yellow and orange wires and got 46 +/-.       

[Terry Carmen]

8 minutes ago, bldn10 said:

I did a little test by unplugging the upper element and then turning it on in Bake. I was able to confirm that the lower (true hidden) element does come on and gets somewhat hot but it seems to be cycling "normally" although the temp is not rising normally. I was thinking that an element either works or it doesn't - it doesn't heat partially if getting full 240V. If that is so, then it would seem that the element is OK but duty cycle is off. FWIW I pulled the plug from the board and checked the resistance of the yellow and orange wires and got 46 +/-.       

240v @ 46 ohms would make it about a 1,000 heater, although I don't know how many watts it's supposed to be.

[Budget Appliance Repair]

On 12/7/2019 at 8:59 AM, bldn10 said:

Resistance is 23.4, 22.3, and 14.3, respectively.

This was the previous listed Ohms for the elements which don't look out of reason.

The 46 Ohm reading between the Orange and Yellow is the reading thru two elements.

You need to remove the RED wire from the relay board DLB OUT then check from the RED wire to:
BLUE - BROIL on relay board
YELLOW - BAKE on relay board
ORANGE - CONV on relay board

Edited December 16, 2019 by Budget Appliance Repair

[bldn10]

OK, thanks, I saw that in a video online and wondered about it. I'd think the best way is to isolate the element from the chassis.

But seems to me that we should be able to determine if it is the element w/ the functional evidence we have. First, does an element either work or not? I.e. no middle ground? On or off.  The Bake element does get hot so does that mean it is OK?

If so, are we back to the board?  

[bldn10]

I finally got a board and just put it in. No difference So I guess it's on to the lower element. 

Anyone need an Electrolux 316443915?    

[bldn10]

I pulled the lower element out and the resistance is 23. Put the original board back in and plugged the lower element in outside the chassis. Now no elements are coming on. :-/

[Vance R]

If they work before you changed the "new" module out. odds would be something in hook up. Need to double check. 

[Terry Carmen]

5 hours ago, bldn10 said:

I pulled the lower element out and the resistance is 23. Put the original board back in and plugged the lower element in outside the chassis. Now no elements are coming on.

Check the plug that goes on the header with no side pieces. It's easy to get in "off by 1" so everything is in the wrong slot./

Edited January 19, 2020 by Terry Carmen

[bldn10]

Hey, good to have you back, Terry.

LOL the power plug was indeed off by 1. I have the original board in now and both the upper and lower elements come on and cycle but neither gets very hot, nowhere close to red. If an element gets even a little hot does that absolutely mean that it is working 100% correctly? If so, I'll try the new board again.  Thanks.

      

[bldn10]

Tried the new board again w/ same results.