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Cherrybark  
#1 Posted : Wednesday, October 12, 2011 3:02:24 PM(UTC)
Cherrybark

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There are two blowers in this dual oven. They are electrically connected so when either oven is on both blowers should operate. The blowers should start as soon as either oven is turned on.

Both blowers work with the lower oven but neither operate with the upper oven. I've done resistance checks on the wiring and everything is good. Nice shiny connectors all around. I pulled the control board and none of the components are scorched nor is there any obvious damage.

My arm still hurts from my wife slugging me when I suggested installing a toggle switch on the face of the oven controls to operate the fan so I'm looking for other ideas. Whirlpool no longer makes the control board for this unit, scrounging for a refurbished board seems iffy and I'm still in shock after looking at prices on new dual wall ovens.

I'm not hesitant to check voltage levels, solder new components or do other work on the board but I have no idea how to diagnose the problem. Suggestions would certainly be appreciated.

Carl
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denman  
#2 Posted : Thursday, October 13, 2011 3:43:10 AM(UTC)
denman

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Here are your parts
Replacement parts for WHIRLPOOL RBD305PDS12 ELECTRIC OVEN | AppliancePartsPros.com

See the attachment for the tech sheet.

Manufacturers do not publish board schematics so I would trace the connection back to the the relay that controls the fan and then replace that.

If you get the numbers/info off the relay you may be able to find one on the net.
A good place to start would be Digikey.

This is a gamble as you do not know if the relay or the board parts controlling that relay is at fault.
You could try measuring its coil to see if that is blown.

I am not a fan of trying to do a live test on it as messing with 240 volts and having parts hanging loose often ends up badly.

Another possibility is to have the board repaired. There are a number of companies that do this, just Google "appliance timer repair".
File Attachment(s):
RBD305.pdf (425kb) downloaded 8 time(s).

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Cherrybark  
#3 Posted : Thursday, October 13, 2011 4:10:46 AM(UTC)
Cherrybark

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Denman, Thanks for going to the trouble to post the wiring diagram for the oven. I couldn't agree more about the folly of doing a live test with parts hanging loose. A hot board touching the oven frame would be an expensive and potentially dangerous mistake.

The numbers on the relays are easily read. I'll let the internet teach me about testing a relay coil. If the relay is clearly at fault I'm off to Digikey.

I'm continue to be in favor of a $2.50 flat black rocker switch but that's been a hard sell!

Thanks for your clear suggestions.
denman  
#4 Posted : Thursday, October 13, 2011 7:49:22 AM(UTC)
denman

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OK if all else fails here is an idea that may be an easier sell than the rocker switch.

Instead of a switch get yourself a normally open thermostat that closes around 100 degrees F or so. Sort of like the ones in a dryer but with a lower temperature and a normally open instead of a normally closed. Should be able to get one at any decent electronics supply house perhaps even some electrical supply. Also Digikey will have them. Just make sure it can handle the fan amperage and it will turn on about 20 to 50 degrees F above ambient temperature but will not turn on at room temperature.

Then mount it above the oven on the protector plate (Item 7 in Section 2 of the parts) or where ever you think it will work properly.
With luck this will be less hassle than installing a rocker switch.

So it will close above usual ambient temperature when the oven warms up and turn on the fans and then it should shut them off again when the unit gets close to room temperature.

Big advantage is that wifey will not even know it is there.
Cherrybark  
#5 Posted : Thursday, October 13, 2011 12:34:43 PM(UTC)
Cherrybark

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Denman, that's an excellent idea. Even I like it better than installing a rocker on the front panel! I have two more questions that I hope won't try your patience.

Do you have any idea what the temps run on the surface of the protective plate when the oven is 350 or how quickly they drop when the oven is turned off? My goal is to select a temp for the cut-off that will turn the oven off after a reasonable time and not run for an hour seeking ambient. I have no clue how good the insulation might be or what the affects of the airflow might be and would be guessing. Of course, I can pull the oven out of the wall and run it if you don't happen to know off hand.

Secondly, I'm in a small town and don't have a decent electronic supply house so Digikey it is. If you don't mind checking, it looks like one of the Bi-metal Cutouts on page 2227 of their online catalog would be suitable. The fans draw .5A each, all of these switches handle 15A @ 120V and half of them are normally open. I'm asking for help selecting the correct "package" to surface mount on the protective plate. Most of the detailed pictures look like they would require a cut-out on the plate or am I missing something or perhaps even have the wrong series of switches.

Thanks again for being so helpful.
Cherrybark  
#6 Posted : Friday, October 14, 2011 3:43:46 AM(UTC)
Cherrybark

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I pulled the control panel off to check the relays and realized this also gave me access to the protective plate at the top of the upper stove so I could do temp measurements as well.

The board uses a very common, well documented relay to control the fans and it was a simple matter to confirm continuity across the two pins that energize the coil. I'm assuming, even with the relay on the board, there wouldn't be continuity if there was a problem with the relay.

I used a electronic, BBQ smoker thermometer (both the meat & air probes) as well as an oven thermometer to measure the surface of the protective plate while the oven was running. After 30 minutes at 350 the temps ranged from around 135 to 150 on the various thermometers. When the oven was turned off the temps dropped very slowly because there is a lot of thermal mass in the oven metal. Even with the oven door open and a small fan running in the open space it took a long time for the temps to drop significantly. I suspect a temperature cut-out switch, mounted on this surface would run the fans for a long time after the oven was turned off and they these aren't particularly quiet fans!

Playing with the lower oven, which does operate the fans, the control logic turns the fans on when the oven is turned on. After the oven reaches a certain temperature, the logic will run the fans for several minutes after the oven is turned off. I'm assuming this delay is driven off the oven temp probe since opening the oven door will shorten the run time.

None of this helps with a simple solution to drive the upper fan, I'm just posting the information for anyone else who comes along with the same problem. There are appliance timer repair companies who work on the control boards for these ovens. The first one I checked had a special note for Whirlpool board, stating they charged double for repairing these units because it was so difficult. Lovely...
denman  
#7 Posted : Friday, October 14, 2011 3:54:36 AM(UTC)
denman

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[COLOR="DarkRed"]I have two more questions that I hope won't try your patience.[/COLOR]
Not a problem.
My friends call me Mr. Jiggery Pokery so I actually enjoy doing mods.

[COLOR="DarkRed"]Do you have any idea what the temps run on the surface of the protective plate when the oven is 350 or how quickly they drop when the oven is turned off?[/COLOR]
I cannot say but if you get one at around 100 to 130 degrees F it should be OK.
It should cool fairly quickly as your fan is up there, I think.
So a test may be the best thing.

[COLOR="DarkRed"]
Secondly, I'm in a small town and don't have a decent electronic supply house so Digikey it is. If you don't mind checking, it looks like one of the Bi-metal Cutouts on page 2227 of their online catalog would be suitable. [/COLOR]
Looked at that page but did not see anything that I thought would be OK.
Who knows perhaps the pages are different depending on your browser (I use Firefox)
Following is one that I think would work.
It is on Page 2224. Specs say it is Normally Open and trips at 105 degrees F with a 5 amp rating.
It could be mounted with a couple screws to the plate just be sure they are not to long.
If the fan then runs too long you could use a couple standoffs under the screws so it measures more of the ambient temperature rather than the plate temperature.
Digi-Key - 723-1220-ND (Manufacturer - C53GAB105A-090Y)
Cherrybark  
#8 Posted : Tuesday, October 18, 2011 9:33:47 PM(UTC)
Cherrybark

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denman,

It turns out the switch is a "non catalog" item and Digi-Key never got back to me with a source. However, Amazon (of all places) had a comparable switch.

For anyone working on this problem, the Senasys 120°F Fan-Style Snap-Disc Switch is suitable and readily available. It is simple to mount the switch on the rectangular flue leading from the blower to the front of the oven. Drill a couple of small holes, use two sheet metal screws, hook up two wires and you're done. The surface of the flue nearest the fan takes a long time to heat up. Mounting the switch closer to the front of the oven, just in front of the wiring harness, puts it in an area with the right temperature range. The blower turns on near the end of the pre-heat cycle, runs for the entire cooking period and turns off after a reasonable period of time when cooking is complete.

Thanks again for coming up with a simple and very satisfactory solution.

Best Regards,

Carl
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