My tail lights on my 1991 Astina dont work!

Replace the turn signal switch.

Check for Power on your License Plate Light, more than likely you have lost GROUND

Turn Signals, Do the Front Work and the Back don't? If NONE then FLASHER FUSE

switch on the brake pedel may be faulty or out adjustment/place

Check your negative connection on the rear lights. It.s like the stop lights are earthing through tail lights and when tail lights are on you have 2 positives.

sounds like a bad ground in the taillamp circuit. The brake lights and the tailights are on different wires.

check the fuses. also check for a bad ground.

Open the trunk and look under the carpet on the driver side and trace the brake wires down for a yellow box about the size of a pack of cigarettes. This is the tail light relay. If you open it you will see the damage. Use a reguar screwdriver. Be careful- the plastic is old and brittle. You can either;
) buy a new one for big buck$
) buy a used one from junkyard ($5~30 ?)
) repair the wires if possible.

If you damage is different than shown then repair that. This is for illustration purposes.

yellow box.
http://files.automotiveforums.com/gallery/watermark.php?file=/503/299469Pic_053.jpg

Opened
http://files.automotiveforums.com/gallery/watermark.php?file=/503/299469Pic_047.jpg

.
http://files.automotiveforums.com/gallery/watermark.php?file=/503/299469Pic_044.jpg

maybe your brake switch under your brake pedal.

From what you just said i dont belive the mechanic checked your fuses correctly.

Check your self to confirm, But if no avial i belive the controller for your lighting may be fried.

Could you take out a bulb and with a testlight/probe check that you do in fact have power to that circuit .Also check that they are the correct bulb for that application I have seen people put indicator bulbs in where therse supposed to be a double filament bulb.Does the base of the bulbs lead contacts line up with the two steel terminals inside the plug?