First of all if all your lights don't work then its your switch I was told on my 94 it was the switch when my tail lights wouldn't work but all my other lights did. if that's your case or vise versa then its a bad ground somewhere. If not there is some mounting hardware under the dash almost where your fuse box is.
On your 1989 MERCURY TOPAZ, the BACK-UP LIGHT SWITCH is: UNDER HOOD, DRIVER SIDE, LOWER ENGINE AREA, MOUNTED ON TOP OF TRANSMISSION
You don't. The switch is all one , you will have to replace the entire switch.
Why ? Just replace it.
Because your switch is bad, replace the light assembly
The headlight switch on a 1993 Mercury Topaz is typically located on the dashboard to the left of the steering wheel. It allows you to turn the headlights on and off, as well as control other exterior lights such as the parking lights and fog lights. If you are experiencing issues with your headlights, it is recommended to check the fuse, bulbs, and wiring before replacing the headlight switch.
To replace the dome light switch on a 1998 Mercury Tracer, first, disconnect the negative battery terminal to ensure safety. Then, remove the dome light assembly by gently prying it down from the ceiling. Disconnect the wiring harness from the old switch and replace it with the new one, ensuring a secure connection. Finally, reattach the dome light assembly and reconnect the battery terminal.
Its just a geuss. but on my 93 mercury topaz the head light switch alsoe controls the lights in side the care. If it's clicked all the way on that might be why.
This is usually cause by a stuck brake light switch on the brake pedal. Replace it.
To replace the light switch on a 2007 Mercury Mountaineer, first disconnect the negative battery terminal to ensure safety. Remove the trim panel around the switch using a flathead screwdriver or trim removal tool, then unscrew the switch from the dashboard. Disconnect the wiring harness from the back of the switch, attach the new switch, and reassemble everything by reversing the steps. Finally, reconnect the battery and test the new switch to ensure it functions correctly.
Follow the positive cable wire from the battery and it will end up plugged right into the safety switch.
check your brake lights if they not worhing replace fuse or brake light switch
Get the alternator checked before your battery goes dead.