For several months my chassis heater/AC fan only ran when the selector was set on HIGH. The reason this happens is that the design uses resistors of differing values to select the speed. There is a fuse on the device which will ‘blow’ when it gets too hot. I traced out the Red, Green, Yellow and Orange wires from the speed switch to the fan housing located under the dashboard on the passenger side. I removed the defective switch easily with 2 screws.
The coils of wire are the resistors. There is a pert number stamped on the front ‘E4UH-19A706-AA’. I cross referenced this to the correct part using the Autozone app. Autozone had the part in stock and would deliver it the next day for FREE so I ordered it.
The old part had 2 connectors. One single wire and a multi-connector with 3 wires and one empty. The NEW part only had one connector. I traced out the circuit and discovered that I could move the orange wire from the single and add it to the empty hole on the 4 wire connector and get the same functionality.
Insert a small flat object (I used a jewelers screwdriver) to release the small clip and the orange wire will pull out.
Here you can see the orange wire being inserted into the multi-wire connector. Be sure the clip is oriented as shown. You should hear a click when the wire is secured in place.
After replacing this part, the fan now works normally and I can use all of the speeds!
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