Kitchenaid Electric range oven elements fault

[FunWithPaul]

Hi guys,

I have a Kitchenaid electric free standing range (kerc607hbs8) that is pretty old...

Everything works, except for all of the oven elements.

The way this oven works is that the RED line current powers one side of all of the oven heating elements when any oven function is selected (via a single relay),

and the other side of each element is connected to the BLACK line current through the power relays on the Power Control Board (when they are activated by the control).

Mine doesn't. (the Black line current is never connected to the elements)

Reading online, a common fault is the oven thermostat, should be about 1100 ohms at room temp. It is.

 

Some ovens have a TOD (thermal overheat device) on the back wall of the oven. This one doesn't.

It has two thermal switches under the Control Panel (one turns the cooling fan ON at 165f, and one turns the Black line current to P-6  OFF at 205f.

Both of those are working correctly (at room temp)

 

I purchased a (supposedly) working Power Control Board #WP9782437, installed it, but there is no change.

From what I can tell the P-8, P-3, P-4, P-2 connections on the Power Board are not being connected to the Black line voltage...

I have a nice picture of the schematic, but can't upload it.

You can see it here

https://imgur.com/VBKLnmC  

"I think" the problem is the supply to what is in the blue box (the pins listed above)

If you look at the pic The Red, and Black (added color) lines all test correct, and the green circle is for the temp thermostat.

Does anyone have a service manual for this Range?

Any ideas? besides throwing (EXPENSIVE!) parts at it?

 

Thanks,

Paul

[16345Ed]

Always start with basics. How’s the wall outlet test? How’s power at terminal block, etc...

[reliableappguy]

I would definitely verify power at the terminal block and to the control board.  If you already replaced the control, it appears from the schematic that either the switch is open in the double line break, the 20 amp fuse is open or there is insufficient voltage to the unit which could be verified at the terminal block.

[FunWithPaul]

On 2/14/2020 at 6:22 AM, 16345Ed said:

Always start with basics. How’s the wall outlet test? How’s power at terminal block, etc...

All good.

I have checked the line current at the board, the black 120v into the board is fine,  as is the red 120v at the elements (when bake is ON )

[FunWithPaul]

5 hours ago, reliableappguy said:

I would definitely verify power at the terminal block and to the control board.  If you already replaced the control, it appears from the schematic that either the switch is open in the double line break, the 20 amp fuse is open or there is insufficient voltage to the unit which could be verified at the terminal block.

My first guess was the relay contact points (I could hear it clicking, but no heat). Nope... when bake is selected, the relay clicks and red line voltage IS connected to one side of the elements at 120v.  The black line voltage TO the powerboard is good,  but (I am assuming) the relays on that board are not closing (no signal?) None of them do. But the DLB relay gets IT's signal from the Power Board...  so the Power Board IS activating the DLB...

There are no error messages either. The oven thinks everything is fine.

I am down to the Control Board or the white connection wires (because the control board controls the power board, which controls the elements)

 

 

[ECtoFix]

3 hours ago, FunWithPaul said:

My first guess was the relay contact points (I could hear it clicking, but no heat).

Guessing isn't going to effectively troubleshoot the problem.

Are you testing the circuit using a VOM?

[Vance R]

First thing we need to do is stop talking about and checking for 120 vac.  Need to verify L1 to L2 is 220 vac at the terminal block with a meter. Next step depends on what is easiest to measure. Ideally you would measure voltage at the element to see if you get 220 vac. If that is difficult put one meter lead on L2 at the terminal block, turn on the bake and measure terminal P2 on the board with the other lead. If you get 0 vac the problem is in the board. If you get 220 vac, try the DBL relay next because it is probably close to the main board. The drawing doesn't indicate terminal numbers or colors of wires of the relay. Measure both terminals still tagged to L2. If you get 0 vac on one terminal and 220 vac on the other terminal - Its a relay problem or control voltage problem. If you get 0 vac on both terminals move on the the fuse, same pattern - your looking for a change of 0 vac to 220 vac. Whatever is in between the change of voltage is your problem area.

BTW - Thanks for the wiring diagram. Wonderful job of circuit tracing 👍. It makes troubleshooting way easier.

[FunWithPaul]

Hey All,

Thanks for all the input.

Did I say at the beginning that I AM NOT an appliance repairman?

But I do know how to use a DVOM and understand 120 and 220 voltages.

What I DIDN'T know (at the beginning) was that oven uses two relays to connect the opposing line phases together.

When I said "my first guess" I meant "before I even pulled the range from the counter"...

My FIRST check was to check for line voltage at the DLB (as I could hear it click, but no heat to the elements... I thought "it is the contacts" I have seen MANY failed contactors in my lifetime..)

When any oven function was selected, there WAS line voltage on both sides, and I assumed that meant it was good.

I was wrong.

Had I known that the Power Board was connecting Black line current to the "downstream" side of the relay, I would have disconnected the P-2/P-4/P-3/P-8 plug that feeds the elements the Black line current.

What I was seeing on my first check was Red line voltage on the "upstream side, and Black line voltage on the other. If I knew more about his oven, I SHOULD have had 240v (from either side to GND.

That made me search other places...

Nope, It WAS the contacts of the DLB.

I FINALLY figured it out, just following the schematic, when I realized the working relays on the Power Board were feeding Black line voltage to the downstream side of the DLB...

But , I learned A LOT about this range...

There is no TOD (thermal overheat device) on the back panel, but there is a 20a line fuse (inside black heat shrink) in the Red line, just downstream from the terminal block.

There are two bimetal switches under the Display Board, one turns the black line voltage  to the Power Board OFF at 205f, the other turns the fan (located at the bottom, under the left side panel to duct cool air over the Display Board and Keyboard Units), ON  at 165f.

Common faults:

Temp probe failure. It should be appx 1100 ohms at 75f

The P1 pins on the Display Board come "unsoldered" from the traces, causing no display.

 

I still cant post pics,

if you want to see the Power Board part # WP9782437

https://imgur.com/gallery/E43NMsI

 

 

[FunWithPaul]

On 2/15/2020 at 6:32 AM, reliableappguy said:

I would definitely verify power at the terminal block and to the control board.  If you already replaced the control, it appears from the schematic that either the switch is open in the double line break, the 20 amp fuse is open or there is insufficient voltage to the unit which could be verified at the terminal block.

Thanks reliableappguy,

You were right.

It WAS the DLB.

I had checked for voltage on both sides (when a bake function was selected) and "thought" it was passing line current through.

It wasn't.

I was seeing Red 120v on the supply side (upstream side), and Black 12v on the feed side (downstream side) of the relay.

Thanks for the help.

Paul

[reliableappguy]

Great. I am glad to hear you got it resolved.

[Jake's Repair]

For not being an appliance repairman, you look like you have some kind of electrical and mechanical knowledge. Good job!