Where is the switch that turns on the rear heater blower? No power to the blower.

red lever behind the shifter

the lever is a ground and when in it's full up position it completes the ground for the fan. on some years you need a jumper on the relay board. it is the green wire in this picture (ignore the comment box; picture is from other post) what year is your car?
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go a step further and install a bulb in the dash vent controls so you know when the fan is on. use the heater switch as your ground and pull the +12 from the fresh air fan light. I don't know why the factory did not wire this light; the control panel has a place for a factory bulb and the red screen...
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Cool! I had no idea there were lights there.

The cars only came with the fresh air fan light (blue one). I added the bubl for the red light.