Forum > Heating & Air Conditioning Repair

Checking a window unit fan switch

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JWWebster:
I use aligator clips to check these. I set my meter for ohms and mine has an audible tone when I get continuity. That is a good thang. I connect one lead to the L1 leg usually off by itself on the end of the switch. In the off position I should not get a reading. I turn the switch to fan only and I get a reading between L1 and 1 of the 4 legs on the other end. The middle bar is a dummy post and only holds common wires and L2 (power), no need to check it because it is not connected to anything inside the switch.It is mounted in the middle for convenience and usually has 4 male clips for spade connectors on it. I go to the next position on the switch and I should get a reading on 2 of the posts. One for compressor and another for various fan speeds. Most of the time the compressor leg will be toast IF you suspect the switch to be faulty. It is good to know how to check these and how they work.
. Oh and if you forgot how the wires went remember this: L1 will have one leg of the power cord and the dummy post will carry the other leg of the power. Black is always high fan, blue is medium fan, red is low fan, and yellow is compressor leg to thermostat easily ID'd by the short wire going to the thermostat, a white common from fan goes to the dummy post and a white common from compressor goes to the dummy post. So you have 3 wires on the dummy post total, this feeds both the compressor and fan.the other hot leg goes on L1 and the rest control the speed and compressor. On these newer models with a small computer board the connections are basically the same. These clever folks hide the fuse by the way, under the backside of the board so look hard for it. If you do not wish to spend the money on a board you could hotwire the thing. Tie your 2 commons together with one hot leg and tie black fan(for high speed) and the compressor wire into the other side of the power cord and be cool.  Simple ain't it? LOL
 :2funny:

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