Whirlpool Dryer Can't Change Temperature

[TechnicianBrian]

Model # LEP6646AW0, the complaint was the dryer would only heat on the high heat or air dry settings, and not the low heat. Dryers with multiple temperature selections will often use a device called a bias heater to achieve differing temperature outputs. The bias heater is generally part of the operating thermostat (older models the bias heater may be a separate piece attached to the thermostat) and is in essence a small heating coil. When a temperature other than the normal output of the element is selected, the bias heater will warm the thermostat and cause it to open at a lower temperature than it normally would (element heat + bias heater heat). In this way, lower temperatures (as felt by the clothes) can be produced by a single heating element. This particular dryer had the bias heater portion of the operating thermostat fail open, so the only temperatures that it would produce were high heat (the normal output) and air dry (no power to the element). Replaced the thermostat and now it has all three temperature selections again.


Whirlpool Dryer Cycling Thermostat Part # 3387134

[JWWebster]

I have found that the 2 purple wire conections do not show any continuity even when new. So how can you test this part? They aint cheap.

[TechnicianBrian]

Do a resistance check not a continuity check.  Most handheld meters will not be able to overcome the resistance of the coil (5.6k to 8.4k range per the tech sheet) enough to indicate a closed circuit. If you do a resistance check and read an open or shorted circuit, the bias heater is bad.