Visitoron May 22, 2011
There are several possibilities for one window to be inoperative. These include the switch (mechanical or electical fault), window regulator (bound/siezed), regulator cable (frayed or broken), or the power window motor (burned out, possibly because of one of the previous causes or a lack of or dried up lubricant), and even possible wiring or connection faults. The switch mechanical assembly- the black switch(es) operated in the center console has a set of four prongs on each individual switch which actuate the (white) switch on the printed circuit board in the upward or downward setting. If these prongs, or a pair of them, are broken off, the P.C. board switch will not be moved, in either both or just one direction. However, if the window is not able to be put down, it is not then known if it can be put back up. You can remove the switch assembly from the center console by pulling or gently prying it up, take a small screwdriver and press in on one pair of tabs on either side of the box assembly to disassembl it and test the actual white switches at the P.C. board by moving them in each direction to see if they operate the windows. Inspect the switch contacts, too, as many of the Miata forums state that they sometimes become dirty or brittle and cease to function.
I just replaced the window motor in a 99 Miata, but on inspection of the switch box, and the prongs on the black switches prior to installing the motor, found that two of the prongs on one switch were missing, rendering the drivers side window unable to be lowered. Once down, however, it could be raised.
Good luck!
