Bake Element not working. Is it the thermostat or controller board?

[leorosi]

I own a frigidaire professional series built-in oven model CPEB30S9FC1 that is approximately 7 years old. A few weeks ago while cooking pizza at 400 degrees smoke started coming out of the oven after 20 minutes and the oven started to give out a continuous beep and the control panel showed me F10. Clearly the oven hit a high temperature and burned the pizza. The oven was completely unresponsive and would not turn off at which point I had to cut the breaker. After the over cooled down I turned the breaker back on and reset the oven clock. I attempted to use the oven and bake again but the heating element would not get hot at all. I then cut the breaker again and left it off for a few days. I attempted again to use the oven with the same results. Since then I have had the following observations and trying to figure if its the oven controller board or the Shut-Off thermostat.

1) When I kill the power to the oven with the breaker and leave it off for a few hours then turn it back on, the bake element works until it reaches the temperature I set at which point the element goes off but it never comes back on again. No F10/Runaway Temperature.

2) Broil works and the broil element works 100% with proper temperature. The broil element goes on and off as expected when the desired temperature is reached. No runaway when the broil is working.

3) I checked the OHMS on temperature sensor and it comes back back normal at approximately 1K (per company spec).

4) I verified the bake element and it works 100%. No issues.

5) I checked electrical power on the bake element terminals with the oven running and set at 350, and there is LOW power...

Here is where things get complicated.

1) Although I have the electrical schematic of the oven, It's not easy for me to trace the wires coming to the front of the oven on the controller board to see if the thermostat has continuity. I know the thermostat is in the back off the oven but pulling out the oven to test it DIRECTLY is NOT easy. The previous homeowner poorly installed the oven and would require me to dismantle a huge section of my kitchen cabinet to pull it out and so Im trying to trace the wires to the controller up front.

2) I don't see any electrical issue with the controller board (cold solder, burned relay) and the board works properly in terms of the time, buttons, etc but don't know of a way to properly know if the electronic temperature controller works or not.

So...

If the issue was the thermostat why would the broil element work 100% and not the bake element? Is the thermostat also connected to the broil or does it work separately for some reason?

If the issue is the controller board why would it work for broil and not bake? Wouldn't it simply not work for either and also have issues with keeping time, buttons not working, etc?

I'm trying to minimize my cost and time in repairing the oven. The controller is real easy to replace but if I buy a new controller and its not the issue I'm out $300. Of course if it is the issue then I'm ahead of the game in other ways..

If I assume it's the thermostat and go through all the trouble of pulling out my cabinets and the oven to replace it while cheap, would easily take up the better part of a day and risk the possibility of damaging the cabinet.

I have read in numerous forums that Frigidaire ovens are horrible and its a common problem but since there are so many variables with mine, not sure how to proceed.

If anyone has any idea about better diagnosing the controller I would greatly appreciate it...Thanks so much!

[AJ]

Is the thermostat also connected to the broil or does it work separately for some reason?

Bake and broil use the same thermostat.

If the issue is the controller board why would it work for broil and not bake?

Bake and broil each use a different relay.

The controller is real easy to replace but if I buy a new controller and its not the issue I'm out $300.

Not if you purchase it from www.repairclinic.com or www.appliancepartspros.com as both let you return any part for any reason for up to 365 days after purchasing it. Even if you installed the part and it did not correct the problem, simply return it.

[tgoods]

The control is easy to check.  When calling for heat check for voltage between the black L1 wire and the yellow bake wire.  If the relay is open, you'll see about 240vac. By what you're describing, it's 99% a bad bake relay.

[AJ]

Another option if it works for you is to see if http://fixyourboard.com can repair the board, unless you can replace the bake relay yourself.

[AppTek]

I fixed one of those today. Bake relay was ok and broil relay was not closing. Desoldered and replaced the broil relay.
I see a lot of bad solder jobs on Electrolux boards. Usually fix them on site.

[niobrara]

You carry relays for control boards ?

[AppTek]

We carry some. I order omron relays from a local electronics shop. Some we recycle from used boards.

[niobrara]

How due you warranty the boards you repair ? I have a bunch of bad ones that I save for what ever reason,but have never tried to repair one .

[leorosi]

Out of curiosity, this morning I turned on the oven to bake at its maximum of 550. To my surprise it actually started to heat up and the whole element glowed full red. No issues around the feet(s) of the element so the element is good.

However, after 15 minutes, the F10 runaway alarm went off. The element would not shut off and still glowed red. I had to shut oven off from the breaker.

A few hours later after it cooled down, I again started the oven again at 250. Nothing. Then 350, nothing. Then again at 550 it started working and heating up again full blast. I did not let it go to runaway temperature, instead after 10 minutes, I set the temperature down to 350. The oven gave out its "temp reached" beep since it obviously achieved it with the oven originally set to 550 and the element turned off. I heard the relay switch off as well as the bake element panel indicator going off. I left it running at 350 to see if it would go back on. After 30 minutes, the temp inside went below 350 to around 200 (i used a cooking thermometer to check) but the bake element would not go on.

So it looks like at full power (550 degrees) bake element fires up but wont shut down. At a lower temperature it does not start at all but from 550 and going down, the oven does detect proper temp and turns element off.

I let the oven cool down again and this time just used the broil element and it fires up properly and turns off when the desired temp is reached..

Does any of this make sense at all? Does it still point to issues with the controller board?

Thanks

[AppTek]

That is strange. You may have 2 problems? If the element does not always come on, it may be a relay on the board. I have seen them intermittent. Broken solder joint that connects sometimes. Also, after an over temp shut down the safety thermostat may be slow closing.
The over temp sounds like maybe the sensor or control board. Check resistance of the sensor at room temp. and as the oven heats up.  Sensors are cheap. You could always try a new one.

niobrara: I have not had any issues thus far. Lol lucky I guess. Also I only warranty the part I fix. If the board develops another problem later it is not warranty. I do tell the customer that if it fails in 90 days then i will credit the cost of the timer rebuild only against the cost of a new board. The service call and labour to remove/install the board is extra and non-refundable.

[tgoods]

I still think is just the relay.  Relays fail in two ways, either they fail to close or they stay closed and fail to open.  You have a relay that's doing both.

[AppTek]

Tgoods, I never thought of that. Very possible. I have not seen any stuck closed yet myself but if the relay is broken inside, the switch could be floating around.