Model #PLES389DCB, the convection fan on this slide in range would not work when a convection cooking cycle was selected, which made this particular cycle unusable. The customer noted all the other cycles seemed to work just fine and called Frigidaire to schedule a service call. The technician that arrived did a few checks (according to the customer) then determined the fan had failed and needed to be replaced. The estimate was more than the customer had expected and decided to do some checking online for a second opinion. I began working with this customer on the problem and after a few electrical checks we determined the fan motor was not the problem, but rather the control board was not powering the fan. Not the answer the customer wanted to hear, but at least the correct part was getting replaced. Here is how we determined the failure.
The convection cycle on ranges equipped use one or more motors to drive fans that create convection currents within the oven cavity. These currents ensure the entire oven is at the same temperature and allow for more items to be cooked at a lower temperature. The big benefit is more even cooking on delicate items such as cookies and cakes, and they can be cooked on every oven rack at the same time. The fans are usually surrounded by a range part called a convection 'halo' element that provides for the heating during the confection cycles after the initial oven preheat.
Because the problem seemed to be with the motor itself, which is located on the back of the oven, it can be difficult to access to do any real troubleshooting because the oven itself must be removed from the cabinet. Not a big deal if the motor turns out to be the problem since you need to get back there anyway to replace the motor, but first I suggested we use a multimeter to do some basic electrical checks before to much appliance moving takes place.
The control boards on these ranges are easily accessed by removing the surface unit knobs and then the large plastic screws that hold the panel to the mount behind. Once loose, the panel can be tilted toward you giving easy access to each electrical connector and to the board itself. Using the wiring diagram as our guide, we can see the circuit can be checked by measuring the resistance from the wire connected at pin 7 and any white neutral wire. The customer did a check between this red wire at pin 7 and the white wire at pin 5 and measured about 38 ohms which indicates a complete circuit through a load. Now the convection element is in parallel with the motor and will read some resistance too, so you would want to ensure the resistance for both the motor and the element were being measured. One way to do this is reverse the leads on your meter and you will only be measuring the motor because there is a diode on the line to the element. This diode only allows current to flow in one direction so your meter will read the element and motors resistance in one direction, but only the motors resistance in the other direction. Neat trick if you know it's there.
Based on the customers findings, the motor and element measured good, so the next check would be to measure voltage between the same to wires and since this is a 120vac circuit, we should expect 120vac to be measured when a cycle was started. The customer checked the circuit but found no voltage present which indicates the control board is bad.
The customer purchased a new control board from my friends at AppliancePartsPros.com and after installing it into the range, had a working convection fan again. Pleased with the success of this repair and the money saved, I suspect this customer will be doing more little tasks around their home.
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