The brake lights on my 91Toyota Previa will not work. We checked the bulbs and they work.All the tail lights come on but when we press the brake...nothing. We checked the fuse and it seems fine

Probably a blown bulb. Tail bulbs come with 2 filaments. One lights up when the parking lights are on and the other lights up when you press the brake pedal.
Rellace the bulb.

When yu press the brake pedal you activate the brake lights not tail lights. The tail lights are a separate circuit. Check bulbs and fuse, the theswitch.

The brake light side of the bulbs is powered by the brake switch and travels thru the turn signal switch.
If the third brake light works, I would guess the problem is in the turn signal switch.

hi if it is only the one bulb not working/tail light and the front light on same side is working along with number plate and other tail lights may i suggest you replace/check the bulb on defective light as if fuse had blown ? the front light on same side would not be working if you put ignition on and press brake your brake light shoul work ? if so change the bulb as the bulb has two elements inside tail light and a higher wattage element for brake light

Yes, you need to of course check the voltage coming into and going out of the brake light switch, if 12 Volts are there going out and coming in while pressing on the brake pedal, your brake lights aren't getting a good ground or there is a break in the circuit between that switch & the lights.

On occasion the tail lights will work with a weak ground circuit where the Brake lights won't. Best way to determine this is to just hook up the 12 volt tester to the Brake light hot wire & there at the bulb ground, then in an area away from the bulb that has a good possibility of contact/ground.

Really that's it, if the 12Volts is getting to the bulb but it isn't lighting, if you aren't getting the voltage there and the brake switch is hot on both sides when pressed, the break in voltage will have to be traced from that switch to the tail light to find the problem.

good luck.

most rear tail lights and turn/stop lights are the same dual filiment bulb. it is possible for your tail light to work and your brake light not to and still have a bad bulb. I would check the bulb first, your brake light works on the left yes? this would mean that the fuse is fine

check fuses

Assuming you tried a new bulb(bulbs can look ok even though they are broken) i would suggest you locate the fuse for that light and check/renew

CHECK THE BRAKE LIGHT SWITCH UNDER THE BRAKE PEDAL

This can be caused by fitting the wrong bulb in your brake lights. Typically a single fillament bulb in a twin ~(Stop and tail) holder. It causes the brake light current to back feed into the sidelight system thus illuminating the dashboard.

Simply fit the correct bulb to cure the problem.

ljbd999