Jenn-Air Broiler Fan Runs Constantly

[b700029]

If you really want to figure it out, trace the PCB and make a schematic.

[drhook]

Hey everybody,
First I'd like to give thanks for the other post on the control board (clock) fix.

After fixing the control board for 23 cents plus shipping everything worked fine. Then a day later the cooling fan and light came on and stayed on. I found the problem to be a short caused by the factory fold in the ribbon cable connected to the same board.

Quick test to verify:
turn off the power at the breaker
drop the front panel
remove screws that hold board and retainer in place
turn on the power
tilt the board upward and back
at some point the fan should go off (you may need to bend the cable straight a little)

Quick fix:
cut a strip of packing tape about 4" long and slide it behind the ribbon and around the front so that the ribbon curls into the connector on the board like it should.

I don't know how long the fix works for but I'll be keeping my eye on it.

[PCBONEZ]

Thanks for the note.
I'm sure it will help someone with one of those ovens in the future.
.

[Longbow]

Thanks for your experiences on this dr. hook. The flex-cable on the timer board isn't all that great and it is easy to push it in off center. I've heard a number of reports of the same symptom happening after the clock display has been fixed. Assuming the connector at the timer board is ok, the "cooling fan runs all the time" symptom is unrelated and so far all the details are still a mystery. The only thing that is known is that the main controller board fixes that problem. Some people just disconnect the cooling fan and leave it like that. But the fan does keep the timer board from roasting. I still don't like the idea of combining microprocessors and ovens, but that's progress for you.

[Longbow]

After thinking about the cooling fan symptom for some time, I think it is worth noting that a likely explanation may have to do with the EEPROM. It is up to the designers, but many generic uPC store the program and user settings in EEPROM. Many articles report how easily EEPROM data is corrupted by timing errors, incorrect power-up and power-down circuit design and so on. Not all of the data is instantly trashed, which would explain how only a few functions might be affected. Each time the stove goes down in a power outage (as an example) the integrity of the data may be compromised.

Anyway, this explanation seems the most likely to me. Since many JenAire owners deal with the fan runs all the time (along with erratic error codes and other mystery behavior), there it is - my guess. The only way to test this theory would be to have a known faulty board and replace the EEPROM with one from a known good board. Since the IC is an 8 pin generic part, good data can easily be read out and stored in a file...and used to re-write a new part.

[bluto]

You might also try replacing the ceramic resonator/oscillator. Its that blue thing marked Y1. I looked and the HD404316 does have internal memory just like the HD404318 on the clock board (although a bit less memory than the 318). So I am not sure why they would need the 8 pin serial eeprom right next to it. Maybe calibration data? The clock board has no such eeprom on it.

I had similar thoughts about a bad micro on my range hood. Turned out the culprit was the 30 cent ceramic resonator: http://www.badcaps.net/forum/showthread.php?t=8654

[b700029]

The HD404316 is programmed by mask ROM, i.e. the program is hardcoded into it at the factory and can't be changed.

Just for curiosity, can you dump the EEPROM and make a circuit schematic? It might help others find a cheap fix in the future.

[Longbow]

I neglected to mention the eeprom number. It is a 93C46 Microwire. the .pdf is listed below.

Making a schematic of the entire controller is beyond what anyone would likely care to do. I did make a partial of the relay control lines just to see if there were any false logic signals between the micro and the fan relay. Nope, the problem is almost certainly in EEPROM. I'm not a software expert but the type of data stored in this arrangement is never certain. User data and calibration is certainly in the eeprom. It is also possible that part of the main program is in there as well.

I do have a faulty board with the old eeprom intact as well as a new board installed in the oven. This eeprom uses a microwire (like an SPI) interface so data can easily be read to a file. At this point the fastest way to test this guess is to just swap the eeproms. Someone with an eeprom reader may volunteer to help on this one also. Strangely enough, the new part comes with a metal shield that mounts between the controller pcb and the back of the oven. The data sheet says that the shield keeps moisture away from the controller board. I don't think I'm dealing with a board that has absorbed moisture. Besides, it would be dried out every time the oven is turned on. Some climates might develop condensation as the oven cools, but that points to other problems.

The timer pcb and the controller pcb work as a team. Just like a lot of home entertainment gear, the timer handles the display and the keypad input, exchanging serial data with the main controller. So why would there be a second eeprom at the timer? Answer: because there is already an eeprom on the controller board.

Finally on the subject of the ceramic resonator. Obviously the whole system goes down if the micro does not have a system clock. But that's not the symptom. All functions work normally except for faulty cooling fan operation and occasional mystery error codes that can be cleared by pressing "cancel". Are you suggesting that these problems are caused by a c.r. running at the wrong frequency? In my experience that would be doubtful. But yes, I did measure the frequency and replace it just to see what happened - no change.

[bluto]

Originally Posted by Longbow

At this point the fastest way to test this guess is to just swap the eeproms. Someone with an eeprom reader may volunteer to help on this one also.

Sounds like fun. If I had the equipment, I would dump mine just to aid in the reverse engineering. If one had the ability to dump the contents they could try all kinds of fun stuff. Maybe zeroing out all (or a portion of) the contents would cause the micro to re-write all the settings. It is possible that, if given the lack of calibration data, the eeproms are installed blank and get populated upon first power up.

Also trying to pin down the root cause, isn't it possible for these chips to 'wear out' after a certain number of writes? So the failure mode being observed is the result of 'bad data' on the eeprom? It says 1,000,000 E/W cycles on the data sheet, though...

But yeah all of my other theories on this thing have been disproved so take that with a grain of salt.

[Scenic]

Originally Posted by bluto

Maybe zeroing out all (or a portion of) the contents would cause the micro to re-write all the settings. It is possible that, if given the lack of calibration data, the eeproms are installed blank and get populated upon first power up.

Certainly possible, but buying a new (blank) EEPROM would probably be easier than trying to erase the existing one unless you already have an EEPROM programmer. Plus if it didn't work, you'd still have the original one.

[b700029]

If you have a PC with a parallel port, an EEPROM programmer can be nothing more than a few wires.

(If I were making one I'd probably separate the input and ouput pins though, just like it says in the datasheet.)

[Scenic]

^ If only it was that easy for 24Cxx EEPROMs.. I might be able to fix my 40" LCD then lol

[b700029]

Originally Posted by Scenic

^ If only it was that easy for 24Cxx EEPROMs.. I might be able to fix my 40" LCD then lol

24Cxx is I2C which needs a few more parts, but it's still pretty simple.

[Scenic]

That indeed looks a lot more simple than what I've found on the net so far (which was mostly ponyprog related)
Any tips for software to read/write the contents?
(mainly for doing backups first in case shit hits the fan..)

[russw]

Originally Posted by drhook

Hey everybody,
First I'd like to give thanks for the other post on the control board (clock) fix.

After fixing the control board for 23 cents plus shipping everything worked fine. Then a day later the cooling fan and light came on and stayed on. I found the problem to be a short caused by the factory fold in the ribbon cable connected to the same board.

Haven't seen any recent updates in this thread topic but I'd like to thank you Drhook for your post. I have a blacked out display on our SVE47600W downdraft slide in oven range and have been researching the issue when I came across Bluto's thread and this one. I originally thought that maybe the display issue was heat related since heat venting from the oven door is just below the display.

I was able to still use the oven "blindly" (tho sometimes I would get a very dim display after the oven had been in use and fully heated) until a secondary problem arose. Sometimes the range would sound an audible whistle which I could cancel but it would start again at various time durations. This would suddenly occur without warning even though the range was not being used. I think I shut off the circuit breaker to stop this annoyance.

Subsequently the issue with the fan running and the oven light coming on simultaneously developed and did not abate unless I shut down power to the range. Powered on the light and fan run continuously and control panel buttons don't respond. The last operation with the range was to run the "Clean" cycle which seemed to function as designed.

I now know how to get at the related control board and will check and replace caps. I will also check that ribbon cable to see if that affects the fan/light issue thanks to you.

Russ

[mike101650]

got lost on first post so this is a post so that I can post.

[russw]

Re: Jenn Air SVE47600W downdraft slide-in range issues posted above.

"I now know how to get at the related control board and will check and replace caps. I will also check that ribbon cable to see if that affects the fan/light issue thanks to you."

Upon accessing the control panel after removing the knobs and the unscrewing the heat element controls for each knob I discovered that a rodent had chewed through the flex ribbon cable on the left side which effectively disconnected the first 3 or 4 traces in the cable (see pic below). Because there appeared to be no easy way to repair this damage the membrane keypad assy had to be replaced. The 4 caps on the clock controller board were also replaced.

After reinstallation, everything was back to normal operation. So apparently the issue with the continuously running fan and oven light being on is related to those first four flex cable leads as well as non-functioning keypad buttons. More details on that issue posted in the Dim LED thread.

Note almost empty bottle to left of range on countertop in 3rd photo which facilitated installation.

[Kyrie]

I'm posting just to offer the details of my recent experience with this problem, in case it triggers an "A ha!" moment for someone else:

My oven recently developed the dimming clock problem described in the other thread. It got progressively worse over weeks, until one day my wife turned on the oven, and it appeared completely out to her. I looked at it, and I think it was very, very dim, but not completely out. Certainly, it was unreadable. The odd thing, and the reason I'm posting in this thread, is that the broiler fan was also running. This was the first time that fan had come on at a time when it wasn't supposed to.

I started researching the problem, which brought me here, and to the dim clock thread. In the couple of weeks that went by as I researched, ordered caps, and got around to fixing the clock board, we used the oven blindly, and it reliably turned on the broiler fan every time the oven started to get warm.

I've fixed the clock board problem by replacing the 68 uF cap, and everything seems normal again -- except that the broiler fan turns on at 220 F every time now. I did not replace the other caps on the clock board.

Now I'm living with it as-is for a bit, while I figure out whether the new fan behavior annoys me enough to do something about it. After having to repair that board, I'm not sure I object to this new, more aggressive cooling functionality. But the one thing that I can't shake is that these problems are somehow related. At the very same time my clock dramatically failed, the broiler fan developed this new behavior. The odds of them being unrelated problems seem low. I know stranger things have happened, and that the fan problem could have arisen coincidentally, but man, that's hard to swallow.

I'm left wondering if the failure of that capacitor on the clock board somehow caused a cascading failure somewhere else.

[blfuller]

My Jenn-Air started doing the broiler fan thing as well recently. I did the replacement of the caps a year or two ago. I came across a schematic for the oven and the cooling fan appears to be tied to the "cool" relay on the main board that is located on the rear of the oven. It is also tied tied to a neutral post on a block that interconnects with the downdraft PC board. Not sure if this is the common neutral for the electronics which has a "L1" (for Line 1?), "N" (for neutral?) and "L2" (for Line 2).

There is a fault code table but mine isn't showing any fault codes in the display so who knows what is causing the relay to activate the cooling fan.

There is the "F3" code that shows the problem being the cooling fan on with no oven function selected. It states that Ohm Sensor, wire harness to sensor are the components to check.

[SundayRacer]

Is this schematic for your oven or a generic... If yourswhat is the model number.

Thanks