No heat, took to dealership replaced heater control unit and still I have no heat. The control unit is fine, I am told the wires are spliced somewhere in between the unit and the other end. The previous owner did a real number on this poor car.

What is the heater control unit directly connected to and where is it exactly, I am going to try to figure out what the exact problem is and just would like a general direction. Thanks much!!

 

The dealer should have a wiring diagram.

 

Or you could pick up a set - here is one source: http://www.mazdatrix.com/8manuals.htm.