Jenn-Air Broiler Fan Runs Constantly

[HmeOwnr]

Re: Jenn-Air Broiler Fan Runs Constantly

I have a Jenn-Air single oven MODEL SVE47500 and the problem is that when the oven temp goes on then the exhaust fan runs thus cooling the box so no cooking takes place... look like it needs a new Electronic Clock Control Board. Where can the best price be found for the Oven Control Board p/n WP71001799?

[HmeOwnr]

Re: Jenn-Air Broiler Fan Runs Constantly

I've done a lot of troubleshooting on this problem, which has been reported almost as often as the JennAir dim clock symptom. Although I have not discovered exactly what the problem is, I'd like to summarize the information that is known, so that others might be able to take it farther than I could.

Photos show the original (faulty) board that came with the range (1995). Here is what is known:
1) Correct fan operation is to come on when the oven is set to broil or shortly after initial warmup. The fan will then run until the oven temp again reaches about 200 degrees, then shut off. Faulty operation is for the fan to keep running for hours after the oven is cool, or forever.

2) The problem (as yet unknown) is on the main controller board and is fixed by replacing the board (confirmed) - costs over $200.00.

3) The controller board is absolutely not sensitive to freezing or heating - the only outside sensor used is the oven temp sensor inside the oven. Freezing the temp sensor with freeze spray will stop the fan. Those results suggest that one or more parts have changed value or failed permanently.

4) DC operating voltages are produced on the controller board (13 volts and 6 volts) by linear means and crude zener diode regulation. There are only 2 electrolytic filters on the board (both replaced).

5) The fan is turned on by the uPC which sends a high signal to a relay drive IC (shown) that produces and active low on one side of the fan relay coil. The other side of the coil is controlled by a switched +12 volts, glue logic and other unfathomable logic processes which ultimately are controlled by the uPC.

6) The main uPC "fan on" output (pin 26) and relay drive work normally. The mystery lies in the logic (and lots of it) connected to the other end of the relay coil. Personally, I can't understand why the uPC can't do all the work and just issue one output, but I really have no experience in heat control designs.

7) All indications are that the problem is on the daughter board shown in the photos. Lines to the daughter board go back and forth to the oven thermostat plug (J10) and to the uPC, then back and forth to a calibrating resistor (J9) on the main board. The calibration resistor at J9 is not used on the new controller board and that is the only discernible difference between the two boards as far as I can tell.

8) The daughter board contains 2 ic's and a handful of transistors - one LM339 quad comparator and one LM224 quad op amp (both ic's were replaced). No obviously faulty transistors or resistors. There are 2 SMD caps on the rear (.15 ufd). Found one leaky and replaced with no difference.

Why there needs to be 4 comparators and 4 op amps I have no idea, especially with a uPC and an EEprom. I imagine that at least one function is a precision reference voltage. Another may be a current sensing circuit. I think the decision to run the fan takes place on this board, then is sent to the uPC, but this is not a certainty. There are a handful of transistors on the main board as well. None of them show any signs of being faulty on either board.

The new board comes with a metal shield that fits between the controller and the back of the oven. The sheet that comes with the new controller says that the shield "is to block the path of any potential moisture from contacting the back of the relay (controller) board." Don't know if I believe that part. Why there would be moisture on the back of the oven? It makes a lot more sense that the shield would deflect or disperse some of the oven heat.

That's all I know. The new controller fixes the problem. I hope someone can take this information and find something I missed; at least its a start. There's probably a 10 cent part that has changed value. I don't think that the uPC just forgot a few lines of code; all other functions on the old board, including keeping the oven at the proper temperature, work normally.

Longbow

Hi Longbow,
Can you tell me what supplier has the controller board available at $200? Thanks

2) The problem (as yet unknown) is on the main controller board and is fixed by replacing the board (confirmed) - costs over $200.00.

[gozzard36]

Re: Jenn-Air Broiler Fan Runs Constantly

A Thermo Sensor is a Thermocouple. Also called an RTD.
It's a variable resistor.
Unless a cap is shorted it's not going to change much.
A relay would be used because it's old tech and switching AC to the fan.
The Thermocouple would switch a transistor that powers/de-energizes the coil in the relay which sends power to the fan.
.
Most likely suspects are the thermocouple and the relay (reported working) but it could be the transistor.

Just a point of clarification: The RTD does indeed act as a variable resistor. A thermocouple is a device of two differing metals which creates small voltage differences as temperatures change. These thermocouples also require a reference junction whose temperature is known to be able to extrapolate the voltages with reference to the junction.

[Longbow]

Re: Jenn-Air Broiler Fan Runs Constantly

I hope someone out there can dump a working EEPROM to file. That way we can see if that part is the culprit. The appliance sheet in the photo is correct. But, it is a wiring diagram, not a schematic. There is no schematic on the board except in the bowels of the RobertShaw corporation. Appliance manufacturers don't expect component-level troubleshooting. Couple of other comments: I did study the detailed tech sheet on the microprocessor. It is an early micro that is definitely not a hot item on things like controller boards these days.. One thing I noticed was that there is a special programming language for chips of this series. I've never heard of that chip-level language, but that's not my line of work.

Someone mentioned further back in the thread that the micro is mask programmed and thus could never lose its memory. Well, maybe he works for the manufacturer of the chip, but the tech sheet is full of instructions on how to program the IC, what commands do what, i/o pin definitions, etc. And, the serial interface is definitely not one I have seen. Its not a memory chip, but it does have a large chunk of memory for storing the program. So it now looks like they selected that chip for the on-board memory capacity too.

I've recently become aware that some board materials in older equipment can indeed absorb moisture, or undergo some kind of chemical reaction which turns the board into a chunk of conductive plastic. I came across one board like that. I could measure resistance in the megohm region between any 2 places on the board just by jabbing my probes into it. Cool. However the new oven controller board is made of the same yellow junk that old one is.

One final thing. Some people are insisting that we are dealing with a faulty thermocouple or temp sensitive resistor. This is not correct. The problem is definately fixed by replacing the controller board, which is on the back of the oven. The purpose of the broiler fan (misleading) is to cool the space directly above the broiler element. That space contains the timer pcb. Yes, the fan cools the timer board when the broiler element is ON, runs for a minute or two after broil is OFF, then stops. There is no temperature sensor in the timer pcb area. The control board is nowhere near the broiler area, so the whole thermocouple thing is on the wrong track. But, a new controller board fixes the problem. That's the way it is.

[kc8adu]

Re: Jenn-Air Broiler Fan Runs Constantly

u2 eeprom corrupt?
anyone dump a working board and make a new eeprom for a sick one?

[SundayRacer]

Re: Jenn-Air Broiler Fan Runs Constantly

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

Thanks

[blfuller]

Re: Jenn-Air Broiler Fan Runs Constantly

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.

[Kyrie]

Re: Jenn-Air Broiler Fan Runs Constantly

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.

[russw]

Re: Jenn-Air Broiler Fan Runs Constantly

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.

[mike101650]

Re: Jenn-Air Broiler Fan Runs Constantly

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

[russw]

Re: Jenn-Air Broiler Fan Runs Constantly

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

[Scenic]

Re: Jenn-Air Broiler Fan Runs Constantly

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..)

[b700029]

Re: Jenn-Air Broiler Fan Runs Constantly

^ 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]

Re: Jenn-Air Broiler Fan Runs Constantly

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

[b700029]

Re: Jenn-Air Broiler Fan Runs Constantly

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]

Re: Jenn-Air Broiler Fan Runs Constantly

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.

[bluto]

Re: Jenn-Air Broiler Fan Runs Constantly

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.

[Longbow]

Re: Jenn-Air Broiler Fan Runs Constantly

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.

[b700029]

Re: Jenn-Air Broiler Fan Runs Constantly

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.

[bluto]

Re: Jenn-Air Broiler Fan Runs Constantly

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: https://www.badcaps.net/forum/showthread.php?t=8654