Unlike vented dryers that vent moist air to the outside through a hole in the wall, condensing dryers blow moisture laden air from damp clothing through a heat exchanger. This acts like an automobile radiator, cooling the hot air, condensing the moisture into droplets and then pumping or draining it into a holding tank. When the water light comes on, the tank is full and the dryer stops until you empty the tank manually. If the water light stays on for some reason, there are four possible causes.
Depending on the model, the holding tank on your condensing dryer is either situated on the top left or bottom left of the machine. When the water level rises beyond a set point, a float inside the tank activates a micro switch. This trips power to the motor and prevents overloading delicate electronic circuits. If you forget to empty the tank periodically, when the tank fills up the machine stops and the water light comes on, telling you it’s time to carry out the emptying procedure.
Although condenser dryers have an efficient filtering system, microscopic fragments of fluff may eventually clog the fins covering the cooling coils on the heat exchanger condenser. When this happens, a false “tank full” warning light comes on. If the light stays on after emptying the tank, remove the clip-on panel on the lower front of the machine, and then use a long-handled brush and vacuum cleaner to clean the condenser cooling fins. On some dryer models you can withdraw the entire heat changer by gripping its handle and pulling it out.
If the light stays on after emptying the tank and cleaning the condenser, either the float inside the holding tank is bad, or the micro switch clipped onto the top of the float has burned out. Unplug the machine’s power cord, consult your user manual, and remove both components. If the float rattles when you shake it gently it’s probably serviceable. Next, set your multimeter to the lowest ohms of resistance setting, then check for continuity as follows: Depress the activator on the bottom of the micro switch to close the circuit. Once this is done, touch multimeter probes to both micro switch contacts. If the readout shows two or three ohms of resistance, the micro switch is working and the float is bad. If the readout fails to respond, the micro switch is faulty. Replace the faulty component and reassemble before testing the machine.
If the holding tank on your machine is situated on the upper left side, the pipe leading from the condenser pump at the bottom of the machine may be blocked by a ball of accumulated fluff or slime. In addition, if the appliance is kept in an unheated garage, the hose may be iced up. Once again, this will cause a false “tank full” warning. Consult your user manual and remove the appropriate side panel – usually the left side – and undo the clamp on the hose leading from the condenser pump up to the holding tank. Place a dish under the hose and pour a mixture of warm water and baking soda into the holding tank. In many cases, this will clear the blockage; if not, replace the hose.