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Website owner: 
Dave Harnish
CEO: Gracie (RIP 3-16)
Dave's Repair Service
1911 Heath Hill Rd
New Albany, PA 18833
Email:
drs@sosbbs.com


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The DRSNews

December 2004  
Merry Christmas!

In this issue:  

1) Electronic Control Range Error 'F' Codes

1) 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 pretty well 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 has become pretty famous by now, as it was widespread - and I still see it from time to time. (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 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 we'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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