The
DRSNews
December
2004
Merry Christmas!
In this issue:
Electronic Control Range Error 'F' Codes
Last
month we talked about calibrating temperatures in 'analog' ovens,
so I thought it only fair to mention some of the issues with
electronically controlled, 'digital' ones this month.
One of the built-in features
of these microprocessor controllers is error detection. Most
errors are reported and displayed in the display as 'F' codes,
and these codes are really helpful in figuring out where to start
in diagnosing your oven's problem.
Early 'EOC' ('electronic oven
control') ranges used only 9 or 10 of these codes, and were
fairly simple compared to those being manufactured today.
But the basic 'F' codes have remained [almost] standard,
and even if you don't know what the 'complete' code might
mean, you can use these to at least get to the general
area of the problem.
These codes are just the
letter 'F' followed by a number, that appears in your oven's
display when there's trouble. Often accompanied by beeping, these
usually require attention before the oven can be used.
Many newer codes are 4
digits, with the second pair of characters narrowing the
problem down more specifically. There are so many of these
now depending on range brand, there's not space to cover
them all in this article, but here are the most common two digit
codes:
*F0 - Failed transistor in
control (replace control)
*F1 - Again, internal failure
on earlier models
(Note - many of the earlier Maytag products
(Magic Chef, JennAire, a
few others) threw an *intermittent* 'F1' code, accompanied
by annoying, persistent beeping. For whatever reason, this
often happened through the night, and the first few I
saw drove me to distraction because there were no service
bulletins from the manufacturer on this until it had been
happening for a while (Fun!). Anyway, in these cases, the
keypad will have failed.
One key will usually 'leak'
just enough current to trick and 'confuse' the processor
into this error code. This problem became infamous
after a few years, as it was widespread - and I still saw it
years after it started. You can unplug the membrane keypad's connector to
diagnose this on most models.
*F2 - Oven temp went too high
- exceeded 590F without door locked, or 990F with it locked (On
newer models, indicates a shorted keypad - we call it a 'stuck
key' code. As above, unplugging the keypad connector
will help with diagnosis)
Other F2 causes can be:
*high resistance connection
in sensor circuit - This is one I see a lot, and like an F3, can
be caused by solder cracks on the board. I've soldered literally
hundreds of these since their introduction, and always have
to smile at the manufacturers' literature that tells us these
boards aren't serviceable.
*Sensor exposed to a
temperature of 40F or lower (I haven't seen this one yet, but I'm
told it happens on downdraft units with short vent runs and
a vent damper that doesn't seal well.)
* Interference from cordless
phones (Have seen this one, especially with earlier phones -
usually when the phone was very close to the range), ham
radios, etc. It seems the board's wiring harness acts as an
antenna in these cases. The harness should be run as close to
the chassis (ground) as possible to prevent this.
* Moisture or grease
accumulation causing current leakage across sensor pins on board
(I have yet to see this one, but I'm sure it happens)
*F3 - This used to be the
most common code, and indicates an open or ground in the
sensor circuit. Either the sensor itself is open, or
a harness connection, thermal fuse (some use one in the
harness), or (most commonly) solder cracks on the board at
the pins that the sensor plugs into. Early sensors were a
common source of this problem, but their reliability
seems to have come a long way. I don't see nearly the
numbers of sensor failures that I used to. Normal
resistance readings vary a bit among brands, but if yours
reads somewhere around 1000 ohms at room temperature, it's
probably OK.
Other 'F3' causes:
*many sensors connect with a
plastic harness plug that's located where the sensor leads
exit the oven cavity. This plug, if installed too close behind
the oven wall, can contact the hot wall and melt. I've seen
these really charred 'crispy', and usually eliminate the
plug when replacing a sensor, using small ceramic wire nuts
instead.
*Even a bit of corrosion on
sensor harness plug connectors can cause this problem.
Current flow through this circuit is very low, and it doesn't
take much to disrupt it.
*F4 - Shorted sensor or
wiring. I find very few sensors themselves shorted, but
sometimes encounter an F4 caused by melted harness plugs as
mentioned above.
*F5 - usually another
internal controller circuit board failure,
requiring its replacement (But indicates a door latch
problem on newer ranges).
*F6 - Time-keeping circuitry
problem - can be caused by fluctuation of the 60Hz power
supply (Another rare one - can indicate a
'cancel' key failure on newer ranges).
*F7 - Stuck button or
function key (bake, broil, clean, etc, on control
- another one I don't remember ever seeing - I feel so
deprived!)
*F8 - another internal
problem affecting temperature control circuitry -
yet another reason to price a new control!
*F9 - Door lock circuit on
older ranges - often caused by pinched or melted door lock
switch wires.
Well, that should get you
started on the way back to a normal oven. Be sure you get
prices on parts before ordering, especially on the controllers
themselves. They can be really pricey. Feel free to contact
me if you need help researching one for your oven.
***
I had hoped to have room in this issue to tell
you about some really neat time-saving software I've been using,
but it'll have to wait for next time. I've been trying to keep
these newsletters from getting so long that they become a
burden to you. As those of you know who've been reading this rag
for a while, I can get long-winded! (I see those heads
nodding...)
***
Merry
Christmas! Wise men still seek Him!
Warmly,
Dave Harnish
Dave’s Repair Service
New Albany, PA
drs@sosbbs.com
www.DavesRepair.com
On
December 25, we celebrate a unique Life that was detailed in
writing, far in advance!
'But
thou, Bethlehem Ephratah, [though] thou be little among the
thousands of Judah, [yet] out of thee shall He come forth until
Me [that is] to be ruler in Israel; whose goings forth have been
from of old, from everlasting.' - Micah 5:2, written approx. 700
years before His birth, and only one of about 300 pre-written
details!
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