Model #KESC307HBS4, the customer called for service on this range due to some intermittent heating issues that she recently experienced while cooking for the Easter holiday. Along with the unreliable heating, there was also a distinct buzzing that was coming from somewhere inside the oven itself. A technician arrived to have a look, but he was having some difficulty pinpointing the source of the noise, and why this range was not heating correctly. He asked if I could have a look at it with him and offer up some guidance.
Heating issues on electric ranges can sometimes be difficult to locate because the information generally provided by customers is rather anecdotal and without specific bits of information we can use in our diagnosis. Many higher end ranges use multiple heating elements, or hidden elements during the various cycles to better control the temperature, but these can mask a problem simply because it is hard to pinpoint which element has failed if the one next to it is heating properly. The hidden bake elements are also hard to identify a failure, because the element can fail, but if the broil element is on during preheating, the heat generated will often feel as if it is coming from the bottom of the oven cavity. When attempting to diagnose which one of the oven parts has failed, it is often best to do electrical checks than to simply rely on our senses.
This range uses a hidden bake element along with a dual broil element for the various heating cycles. Each element is controlled by the logic board located under the user panel based on inputs from the temperature probe inside the oven cavity. Oftentimes, when inconsistent temperatures begin to be noticeable to a customer, this sensor is the cause, simply due to it's inaccurate readings. The technician I was working with was of the opinion, the sensor was going bad and the noise or buzzing sound out of this unit was the result of a bake element going bad. Since the element is hidden, he didn't have an opportunity to visually inspect it, but the area the sound was coming from made this a logical deduction.
When I arrived on this call, the noise was the first thing that seemed very out of place and although the heating issue was the reason for the call, I figured I would locate the noise first to get it out of the way. The noise seemed to come from between the storage drawer and the oven liner, which is where the bake element is located. But having some experience with these models, I figured the noise was more likly from the cooling fan on the left side of the drawer. This fan is used to aid in cooling the electronics and it's exhaust is located in the left rear of the cook top. Once the drawer was removed, the sound was definitely coming from that area, but once the housing was removed, I was surprised to find the source was actually a relay.
This relay is the double line break relay which is used to complete the L2 circuit to each of the heating elements. Controlled directly by the logic board, it is mounted remotely and was an engineering addition to this line of ranges to prevent users from getting shocked in the event of an element arcing to the chassis. A check of the relay with my meter showed the sound was the result of the contacts opening and closing very rapidly. The relay appeared to have water leaking from it which is likely condensation trapped inside the housing, which may explain it's unusual behavior. And with the relay cycling at a rapid pace, that would also explain why the oven was suffering from unexplained heating problems. If the relay doesn't remain closed, each element cannot be cycled properly by the logic board and slow or inaccurate temperatures would be the logical symptom.
The technician was able to pick up an replacement relay from our parts supplier and with the power disconnected, installed it in place of the failed relay. With power back to the unit and a bake cycle started, the relay was as quiet as expected, and the range quickly came to it's preset temperature. A test with the temperature sensor on my meter verified the displayed temperature was indeed accurate, so it looks like we were able to solve two problems, by replacing just one component.
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