Frigidaire ovens FEB398WECD

[Tim M]

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I was working on a Frigidaire double electric oven FEB398WECD where the top oven wouldn’t heat at all. She’d had a repair guy in from one of the big outfits for her garbage disposal and he said the it was probably the thermal cut-off, at he could call up Frigidaire and get the part for $80. He didn’t have much time and couldn’t get the thing out of the wall, so she called me.

After a lot of work, we managed to get the thing out, and the thermal cut-off tested no resistance and was working fine. I bypassed the cut-off to double check, and still no heat. The guy who fixed the disposal had made the most likely guess given the symptoms, but that wasn’t it. The temperature probe and the heating element tested OK. It was getting 220 power.

Hmmm. My genius of a brother-in-law, an electrical engineer, jack-of-all-trades, and general fix it guru, didn’t have a lot to say about ovens last time I remember. Online everything pointed to the thermal cut off and I wasn’t finding what I needed on the spot. A search landed me on the Appliance Samurai page that I had been so impressed with before, and I contacted him.

Describing my problem briefly to him, he told me to check the few things I’d tried and then said to work backwards from the element. Check the voltage from each lead and the one that wasn’t giving me its 110, just trace it back from there. I’d need the wiring diagram, he said, but it wasn’t on the oven, or up in the controls. I could download it, but he said it would cause more problems then it would solve if it was for a slightly different model. I found it on some appliance parts web sites, but they were all so blurry I couldn’t read it all. In retrospect, I should have tried going directly to the Frigidaire web site. As much as I like to avoid the internet these days, it’s undeniably useful for manuals and parts.

So I start metering one side of the lead to the heating element and I get its 110V as I ground the other lead from the volt-ohm meter to the stove body. Now, wait a second, it’s gone. I’m hearing a clicking of a relay as it disappears and comes back, so I figure it must heat a little, rest a little, heat a little rest a little (to paraphrase George Carlin).

?? Is that right? Do some ovens not consistently apply power to the element? If not, why?

OK, so now the other lead should be dead. Right? No, I’m getting the same 110V intermittently with the clicking. Alright so I test both leads to each other and get 110V intermittently and not 220. That doesn’t seem right. With some fast switching during a single spaces between clicks, I find that when there is 110V between the leads then the first lead has 110V between it and ground and the second has zero between it and ground. After the click, when there is zero Volts between the leads, it is the opposite: the first lead now tests zero Volts between it and ground and the and the second now tests 110. A puzzlement. Curiouser and curiouser. I couldn’t figure this one out, but seeing as I was only getting 110V between the leads, I believe the Samurai’s suggestion to be the only option and start to trace it back.

?? So can anybody explain to me what I was getting on the meter? It just occurred to me that maybe it was some phantom current showing up as 110V but a fraction of an Amp, but I don’t think so. Should I have a better meter that can tell Amps too? So are the two leads doing what they appear to be and taking turns conducting power, which they shouldn’t be, or was only one operating?

So, without a useful diagram, I take everything apart to follow the wires as I trace it back. One of the wires changes color as it splits into a broil and bake wire behind a piece of tape after leaving the cut-off. I get back up to the relay board and find that the leads to the elements come in right next to the leads bring power into the unit. Guess if I’d thought about it I might have known. Power in is OK. Power out to the element behaving the same as it was at the element. Test the lower oven relay to see how it should be behaving: 220V with each lead getting 110 at the SAME time, as I would expect. OK it’s the relay. I hook up the upper oven’s leads through the lower oven’s relay and control to confirm. Nothing like having (almost) two of everything to teach me how it is supposed to work. Definitely the relay.

?? Was there an option besides replacing the entire board?

I look online for the board with transformer. $259 at Sears (probably more from Frigidaire), $186 from RepairClinic, $124 from PCApplianceRepair. Put it in and it works. Then wrestle the thing back into a hole that is too small less than a week before Thanksgiving.

So I’m hoping to get a bit of an idea, why it was doing what it was doing. Replacing the part and getting it going was satisfying, and I’m still mystified as to what was happening exactly.

[Samurai Appliance Repair Man]

Great job in getting this far! That's some of the best troubleshooting I've seen from a Grasshopper in many moons.

Did you disconnect one lead from the heating element while you were making your tests?

[Tim M]

Yes, I'd disconnected both leads. Maybe because I'd had the element out. Both were disconnected and not touching anything. I hooked the volt-ohm meter up to each about 50 times both because I couldn't understand what I was seeing and to be sure what reading I was getting when it was 110 between the leads and what when it was zero. It was hard to get it between the leads and then between one lead and ground all before a click. Then each time I got a zero reading I wondered if it was really zero or just not making a good connection, but then I'd be out of time. I did it enough on the (disconnected) leads to the element, and then repeated it up on the relay board, that I'm pretty sure about this.

When you get time, I'd love to hear some comments of the paragaraphs with a "??" before them, just for my own education, to help me understand and to help troubleshoot next time.

Goodnight.

[Samurai Appliance Repair Man]

You should be getting power steadily, not cutting in and out like you're seeing. And the fact that you're seeing BOTH lines flicker in time with each other means something common to both is affecting them. Looking at your wiring diagram, one side of the element is connected directly to L2. If it's cutting out, too, then we have to rule out a problem with the neutral connection. Start at the power block and make sure all those connections are good n' tight. Repeat your voltage test on the L1 and L2 lugs on that power block.