Ask Me Help Desk - Intermittent Wall Oven

I own a Frigidaire convection wall oven model FEB386CE. After the oven has reached the programmed temperature and has been operating for a while the broil and bake elements stop working. It appears that once the oven has cooled, they again are functional. The convection element works any time. I note in the wiring diagram there is a thermal circuit breaker together with a relay.

Any idea what the problem is likely to be? Help would be appreciated!

Thanks.

It could be a tempreture sensing probe. Newest appliances equipped with all those electronic controls can be difficult to troubleshoot without a easy to understand wiring diagram.

If I had to guess, a probe should tell the board to call for heat, to which the board would most likley energize a relay, or small contactor to provide voltage to an element. Of course, it may also have to pass through a high limit, as you said, a thermal circuit breaker, relay, etc.

The only way to know for sure is to access the controls and test points. Pull the wiring diagram, turn the oven on and wait for it to kick the elements out, then using a volt meter, perform line to line troubleshooting to see where your voltage stops.

Using a volt pen that labman has advocated using can make checks more user friendly to the novice DIYer. However bear in mind, that your element probobly requires 220-240 volts. You could very well have 120 volts standing on either side of the element all of the time.

This is also why its important (if you use a volt meter) to reference to the other potential of the circuit. This means that holding the black lead of your meter to ground is no good!

Hold the black lead of your meter to one side of the 220 volt circuit. (can be one side of the element) then take your other red lead and start checking the other side.

Can you post your wiring diagram? Or scan it and email it to me? If I had something like that to look at it *might* make it somewhat easier for me to explain. I won't garentee as I hate troubleshooting things that run through a control board, but I'll give it a shot.

A WORD OF CAUTION:

Troubleshooting live circuits line for line can be dangourus if not respected. There is voltage there than can certainly get your attention. I normally kill the power to the machine by a breaker or unplugging it until I have it dissasembled for troubleshooting. Then I make sure I have all of my test points within easy access withough having to stick my hand in dark corners.

Thanks for your help. Here's the wiring diagram.

Well this isn't to bad.

You said the bake and broil element both cut off after so long until it cools. You also mentioned a "convection element" I didn't see this listed on the diagram, all I see is a convection fan. I'll assume that's what you meant.

It sounds like we can narrow this down to a handfull of possibilities.
a) the thermal ciruit is tripping and not resetting until it cools
b) the probe on the board (what detects over temp) is faulty and making the board think the temp is correct in the oven
c) the board itself is faulty. I can see that your relays for both elements seem to be built into the board, so if it tuned out to be a relay, then you would just have to replace the board anyway.

To find out, disassemble the oven to access the nessesary test points. Make sure you kill the power to the oven while you do this for safety. Once you have everything out where you can reach it easy, reapply power and allow the ovens malfuntion to occur so we can troubleshoot it.

That relay you are talking about seem to be for canadian models only from what I can see.
Plant one lead on your meter anywhere on the L1 side of the circuit. The incoming power terminal would probobly be best. Then using the other lead, check for voltage on both sides of your thermal cuircuit breaker. If you have voltage on both sides of the thermal circuit breaker, this is not your problem. Check the canadian relay in the same manner. If voltage is present there, then finally check the L2 side of the element. (note- you other meter lead should still be on the L1 incoming supply terminal block), if voltage is present there, then that side of the circuit is in working order.

Once we reach that conclusion, take your lead off L1, and plant it on the L2 incoming supply terminal block. (basicly switch it around so we can check the other side of the circuit)

Refrencing to L2, test for 220-240 volts on test point E6 and test point E7 on the terminal board. If there is not voltage there then the board is not closing the relays allowing the elements to energize, this could be due to a faulty board, or faulty probe.

If there is voltage there, then finally check for voltage at the L1 side of the element, if there is voltage there then the element should be heating. If not, then it would have to be a faulty element, but I really don't think that's the problem. If there isn't voltage at the element, but is voltage on the terminals I mentioned above, then you probobly have a loose wire somewhere.

Now, back to the board, if no voltage is at E6, and E7, then we must find out why those relays aren't energizing. Id check the probe, and ohm it out, check for resistance. If the prove is open or closed all the way, its faulty and should be replaced. If the probe checks good, then it could be the board itself. Its rare for boards to fail, but it does happen.

I have made some alterations to the diagram you send, scanned it and am reposting it here for your review, I have color coded the points of interest.

L1 potential is green
L2 is red
The probe is blue
I have "X'ed" some possible test points.

Hope this helps.

Remember my word of caution, do be careful when doing these test, you are working with live voltage, and injury could result if not practiced with care.

Awesome... Thank-you very much for your help. I live in Canada and thus it is the Canadian model...

Is this another good reason for avoiding anything with digital controls?

Quote:

Originally Posted by labman

Is this another good reason for avoiding anything with digital controls?

Im thinking that you don't have much of a choice anymore, seems like everything is digital.

I deal with food equipment each day that I feel horribly overcomplicated and over enginerred. All for more bells and whistles.

Then you get into repair cost. I can only imagine what the cost of that board is when companred to an good old fashined mechianical t-stat.

I looked around this summer before buying a water softener. I didn't see ANY that weren't digital.

Quote:

Originally Posted by labman

I looked around this summer before buying a water softener. I didn't see ANY that weren't digital.

To bad I don't work on water softeners. Nice to know there is still hope.