94pt 'cool o matic' gally exhaust fan

[Gregory OConnor]

The thermostat output wires probably doesnt even power the fan. most likely it powers a bosch relay.

• there is a fuse for the thermostat power (above driver sk10) this power wire to the thermostat is green
• and a fuse for the fan relay power (above driver sk10) power wire is orange/black.
• The fan relay switch (K8,a bosh relay above driver) gets a 12v signal from the thermostatfixture to send another source of 12v power power(sk10) to the fan
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The thermostat sends a signal back to the relay above the driver. that signal causes the relay to make contact and connects the sk10 fuse to the fan. the potentiometer at the fan then dictates the speed. for the fan to work both fuses the relay and the potentiometer must check out ok.


you can test the fan inplace by hooking it up to a portable carbattery jump pack. if it runs it still may not be good, could be drawing too much amps and the reason some issue of power faulted in one of the fuese, relays or potentiometer.


an ampmeter between the battery and the power should prove draw ( I dont know how to measure amp draw). My fan has a lable that says 8 .5 amp full speed.


since the fan is not powered directly by the thermostat I can not relocate the potentiometer to the thermostat wall.


Greg94ptCa