The Blower Motor Plug or Blower Fan Switch Plug is found in Subaru models that utilize a manual air conditioning system. The simplest way to tell the difference between manual AC and automatic AC is by how the temperature is controlled. With a manual setup the dials adjust temperature, fan speed, and direction and stay in the position selected by the user. With the auto AC models, the temperature can be set and the system automatically adjusts to match that temperature based on a number of inputs.
What does the Blower Motor Plug Do?
When the AC fan speed setting is selected in a Subaru there’s a switch that controls how fast the blower motor fan spins. This works by adjusting the resistance on the ground side of the circuit. The lower the fan speed, the more resistors the circuit must pass through thus less amperage makes it to the blower so these settings are "safe". However, when at full blast the ground circuit makes direct contact between the ground on the chassis and the blower motor fan which means the switch is passing through the maximum current which generates heat and the connector has to absorb this. So what happens is over time the pins burn out on the high setting.
The burnt pins can look like this:
If this should happen to you, no worries because iWire has you covered. We sell this replacement plug (link to purchase below).
How does this problem get solved?
Hard to say what the root cause is so other than a repair and hoping for the best we can't be totally sure. Our best guess is that the ground side of the circuit isn't grounded that well which causes a back up in the system which generates even more heat (think putting a finger over a water hose) and pushes the connector and switch past its limits. It could also be the switch itself just doesn't pass the current through well enough and over time it gets worse which causes the failure. One thing to do is make sure the ground circuit is well grounded and even an additional ground point might help.
This plug is compatible with all Subaru models with Manual AC from 2005 to current. If you aren't sure, feel free to contact us.