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Earlier I mentioned that the stove doesn't work. This evening we took it apart.
We took out the burners and tested as much as we could with a multimeter. Our major finding was that the previous owners used this thing as a grill A LOT and never ever opened it to clean. I used this opportunity to scrub the bejesus out of a lot of it.
Anyway, the problem we've seen is this: when any of the burner controls are turned on, the "caution, it's hot" light will illuminate and that's it. The burners stay cold. We determined that the modules themselves were fine - they are of a very simple design, too, so we could quickly tell they were fine.
Next we found how to take the control unit facing off. Wow, that's a lot of wires... and a heck of a lot of grease. Sadly, the complexity has so far defeated us. We're trying to figure out, given a multimeter and a broken stove, how the thing should once have worked. There are no wiring diagrams available on the net. The stove manual, which of course we still have, is not very detailed and says only to install the stove "in accordance with local codes".
We got as far as trying to remove the top facing before we realized that was probably the only thing holding the guts of the stove up, so we sheepishly put a whole bunch of screws back in.
More on this later, I hope.
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| Interior Wiring |
We took out the burners and tested as much as we could with a multimeter. Our major finding was that the previous owners used this thing as a grill A LOT and never ever opened it to clean. I used this opportunity to scrub the bejesus out of a lot of it.
Anyway, the problem we've seen is this: when any of the burner controls are turned on, the "caution, it's hot" light will illuminate and that's it. The burners stay cold. We determined that the modules themselves were fine - they are of a very simple design, too, so we could quickly tell they were fine.
Next we found how to take the control unit facing off. Wow, that's a lot of wires... and a heck of a lot of grease. Sadly, the complexity has so far defeated us. We're trying to figure out, given a multimeter and a broken stove, how the thing should once have worked. There are no wiring diagrams available on the net. The stove manual, which of course we still have, is not very detailed and says only to install the stove "in accordance with local codes".
We got as far as trying to remove the top facing before we realized that was probably the only thing holding the guts of the stove up, so we sheepishly put a whole bunch of screws back in.
More on this later, I hope.
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Your controls - part number 240P-871 - show up in a cross reference table on page 236 of this catalog (http://www.marcone.com/resources/catalogs/range.pdf) . The crossed part number is 5501-333.
There's a diagram of how this type of "infinite control" ( there's your problem - division by zero... ) works on page 227. That shows 5 contacts that might help you decipher how yours is connected.
Page numbers given are from the status bar in Acrobat, not the listed page numbers in the text.
Breaker OFF for the first test here!
I'd suggest you ring out from the burner contacts ( heating coils removed for access ) to the back of the controls to verify there isn't a broken wire or similar.
Then with breaker back on, check for 240 VAC ( let's be careful out there... ) across the appropriate contacts on the back of the controls.
My guesses - either you've lost a leg of the 240 coming into the stove or the controls are defective. If ALL of them are nonfunctional, but the heating elements seem to be a reasonable resistance, then it's likely that the supply side power is the culprit. If this has gone bad one burner at a time, then look to the controls.
And hopefully this is coherent and at least somewhat helpful. It is rather late here, so no guarantees.
Good luck.
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Check under the counter for a large wall plug. It might be direct wired, but an oven style plug would make sense.
Measure voltage from the angled holes to the more rounded hole. Or to the center one if there is no ground ( ie rounded hole ). You may have lost half of a breaker. The indicator light might work with only half the voltage present, but neither burner will.
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* Yes, they are in Norway so it would be a bit of a trip, but a great story. I do actually know someone who lives in the same building as the pot-stirring guy.
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*nod* Yeah, we looked at the connection to house power first. Sadly, it is indeed direct wired.
Half of a breaker? How would one "lose" half of a breaker?
I'm curious: if half the voltage is present, wouldn't the burner get somewhat warm? After all, those high-to-low-temperature control knobs are just big potentiometers.
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No broken wire from burner to the back of the controls. However, no 240 coming into the module plug blades (we didn't check behind the controls with the breaker on). We checked those before we understood which blade was which, and were confused to see around 120 occasionally. I bet you're right about one leg of the 240 being dead. (And yes, ALL burners are nonfunctional.)
How the heck do you lose one half of the power...? I guess that's a question for an electrician, unless we can see an obvious problem at the breaker box (we haven't seen anything obviously wrong there yet).
Thanks!
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Heh, heh. That's what I get for making assumptions.
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The 240 VAC breakers have 2 sets of contacts, one for each "leg" of the power coming in. Since the burners use no neutral, if one set of breaker contacts has quit working, you'll see no heat. ( For reference - houses are wired across a 240 VAC center tapped transformer. The neutrals go to the center tap. )
If you check diagram on the catalog page I pointed to in my first post you'll see that the controls are not just pots. They're little thermostat sort of things. Rather clever - and thanks for posting this problem BTW - I learned something new too.
This arrangement makes sense if you consider that in order to do the trick with a pot, the pot would have to dissipate all the energy not sent to the burner when the heat is set to anything but "full". Lots of waste heat that way - at the knob. A bit of a hazard to the cook. The on-off method only sends what's needed. I'm guessing the cycle time must be pretty short for the range top versions. I've never noticed one cycling.
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Good point.
I've never noticed one cycling either, so I too would guess the cycle time is pretty short. This is interesting! I've never thought much about how stoves worked.
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Thanks!
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Now at least we know not to call Jenn-Air; the stove itself is fine.
Thanks!
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I disconnected the red from the system to make sure there wasn't any kind of high-resistance short. No change.
How do you think we could have a partial-voltage failure?
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It now looks like our stove is fine and the power it is getting is at fault. It has enough power for lights, but not enough for burners. I'm not taking apart the breaker box, so it's time for an electrician!
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Corrosion or a loose connection ( leading to oxidation, etc ) at the breaker would be the first thing I'd check. This would be high resistance at a connection somewhere. Which incidentally would tend to get very hot at high currents.
A damaged wire between the breaker box and the stove is another possibility. As would be the splice where the stove connects to the feed wire. ( grease in the wire nuts maybe ? )
Exercise caution in the following. Don't work alone, electricity is bad for you, etc. ad naseum...
Oh - the red wire's connections at the breaker and at the stove top are obviously suspect at this point.
Set the DMM to 600 Volts AC and probe the terminals on the breaker that feeds the stove. Some breakers have set screws that you can probe ( near where the wires connect ), some you'll have to stick the probe tip in where the wire connects to the breaker. You should see 240 or a reasonable facsimile. If not, the breaker is suspect. Verify by probing across each breaker terminal to the neutral bar. You should see 120 at each terminal on the breaker, but if it's bad, the 27 volt reading or similar will show up again.
If there is no obvious problem on the output side of the breaker, you might have a bad contact on the back side of the breaker. I mention that just in case nothing else has cropped up. Hopefully whatever is wrong will be obvious in a visual inspection.
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At this point oxidation or a damaged wire seems like the likely cause. Maybe one of those squirrels that gets under the house. I've decided to delegate to an electrician, because I don't feel like crawling under the house, and don't feel like I want to open up the house service circuit breaker box. He's coming tomorrow morning. We'll let you know what happens.
Thanksgiving masacree!
Turns out that the oven was (correctly) wired across two phases, and that one phase was gone (out at the pole.) Engaging the thermostat completed a circuit through the oven to power the streetlight (which was on the "dead" phase.) (I know a similar, earlier story of a laundry dryer having similar effect - house lights came on dimly when the dryer was heating, off otherwise... in that case, a neighbor had apparently backed into the power junction box coming into the house and cracked one of the feeds...)
So, I don't know if this *helps* you at all, but yes, losing a phase is entirely possible. It occurs to me that the circuit breakers I've seen for this are usually a ganged pair (so when one trips it mechanically throws the other one); so you *could* conceivable have lost "half" a breaker - I'd probably try flipping it off and then on again and checking the line with a meter, though I'd then leave it *off* because
The risky scenario is that if the breaker blew because a squirrel ate through one line and shorted it... it may still be shorted and if the (possibly damaged) breaker doesn't reopen fast enough, it could catch fire. That's the reason you probably want to leave it to a (licensed but more importantly insured) electrician...
Re: Thanksgiving masacree!
Okay, now THAT'S good correlative reasoning -- and a darned funny story, too, from the safe "distance" of the future!
And yeah, we have a ganged breaker pair on this one. We've turned the breaker off and on numerous times; whatever's going on, both sides of the breaker are perfectly happy with it. Given the voltages I've seen, this makes me think the failure is out past the breaker box toward the street. Anything inboard of that should be making the breaker very unhappy.
Electrician is scheduled to arrive in nine hours. :)
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Nice to see that all those times I bugged the crap out of repair guys by following them around asking how stuff works are paying off once in a while.
:-)