Make sure that the work area is dry but away from a direct heat source. Make sure there are no open wires from other appliances. Remove collector cells and prefilters so that you can get into the unit. Open up the panel and look into the box. If LED light is on, push the "Test" button. Listen carefully for a light ticking sound. If there is a sound, check to see if the LED light is on in the W8600E Panel. If so, proceed to Step 4. If not, proceed to the next step.
Check the wiring in existing W8600E panel by removing and reconnecting wiring from panel to the heat exchanger. Clean the area of debris with a brush. Connect the wires using this color code: 1(G) to 1(G), 2(Y) to 2(Y), 3(R) to 3(R), 4(B) to 4(B).
Press the "Test" button to ensure that the light comes on. If light does not come on, replace with a new W8600E panel and re-wire as described above.
Replace cells and pre-filters. Close the door to the access panel.
Turn air exchange machine back on. The "Wash" light should come on. Repeat steps if problems persist.