3 speed attic fan switch


my attic fan switch just gave out and we are attempting to wire a new one in. The fan has hi/low/off but there are 2 red wires, 1 blue wire and 1 black wire coming out of the new switch. The way it is wired now, it will go on low and high but not turn off. He is unsure about what to do with the blue wire? how should this be wired?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

For Master Flow fans...
1) black is hot 2) red goes to the low speed wire on the motor 3) blue goes to the high speed wire on the motor
the switch is just a simple SPDT switch with an additional "off" throw, but mechanically the switch always forces you to "pass through" "High" before getting to "Low". This is so that the fan motor always has enough starting current to get it going at high even though the user eventually wants it on low. So getting the wires correct is important for the life of your motor, you dont want it always starting in low. Dont go by colors though, test your switch with a multimeter. Make sure that the first wire to get energized when leaving "off" gets hooked to the "high" speed wire on the motor.
so how your switch works...
1) in "Low" the hot supplies current to the red wire 2) in "High" the hot supplies current to the blue wire 3) in "Off" the hot is disconnected
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Didn't the replacement switch come with a wiring diagram? Did you check online to see if you can find one? Without one, it would only be a guess as to what goes where. First thing I'd try to do is identify the incoming side of the switch. It's probably the black wire. The fan should have 3 wires going to it, one for high, one for low, one neutral. The neutral normally doesn't go through the switch and is wired directly to the incoming white neutral. That means two wires from the switch should go to the fan. With a simple test meter you should be able to figure out which of the output leads is high and which is low speed.
As an aside, is this an attic fan or actually a whole house fan? All the attic fans I've seen were one speed and had a simple thermostat switch.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.