Chosen Solution
Dryer throws a F40 code 4-6 seconds after startup.Replaced Thermal Fuse and Thermoresistor (Both new and old fuses had continuity when checking with a multimeter.Checked circuit board, apparently had been replaced somewhat recently (past couple of years). Heard about the burnt relay on the board as a possible issue (previous board might have had a burnt relay and that’s why the whole board was replaced), but found nothing wrong, all connections looked good. Service manual said blower motor but the model doesn’t have a blower motor, the same drive motor that turns the drum also has a belt that goes to where the blower motor would be on other models. There did not seem to be anything wrong with the drive motor, had difficulty figuring out how to check between the phases. Model 110.78062801 with Steam.
Hi, Perhaps the best way to check the drive motor is with an AC clamp ammeter to measure the current through the motor. (supplier example only to show the meter) Looking at the schematic on p.16 of the Tech Sheet W10156035A for the dryer it shows the connection of the two windings. Initially the windings are in parallel until the motor runs up to speed and then the centrifugal switch operates and disconnects the start winding. The current through the motor will be nearly double the value on start to what it is on run. I’m wondering if the control board monitors the current through the motor and if there is a problem with say the centrifugal switch not operating and leaving the start winding in circuit that it detects this and stops the motor and gives an error code. It could also be a faulty winding but measuring this would be difficult as their specific resistance values aren’t shown, just within what range they could be. I suppose that you could measure the combined parallel resistance and check what you get. It could be anywhere between 0.56 Ohms and 1.35 Ohms though. Anything outside this range would indicate that something is wrong. Maybe too low a resistance to measure with a standard Ohmmeter but you can only try. Disconnect the wiring harness from the motor and measure between 4M and 5M (or 3M) on the motor terminals
