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I have a 92 Suburban Silverado.
Taillights come on when headlights or parking lights are on, but don't don't light up when pump the brakes or for turn signals. I have replaced the bulbs, turn signal switch, circuit board for tail lights fuses and relays. Still no rear brake lights or rear turn signals. Now what?
Do you have only front hazard/turn signal operation? Or none front or rear?
If none at all, try this.
Your truck does have a dedicated STOP/HAZ fuse (15A, will be blue) so make sure you've checked that one specifically.
Next component in the circuit to check is the stop lamp switch. (You didn't mention inspecting or replacing that.) I suspect the circuit could be open there. Either burned contacts from usage, or the plastic retainer or housing has become brittle over the years and broken or moved out of correct positioning. Make sure you have B+ at the orange wire cavity of the brake switch connector then jumper the circuit to the white wire. You're bypassing the brake switch by doing this. Do you now have brake/turn signal/hazard operation? If so, it's the brake lamp switch.
*A side symptom of the brake lamp switch being faulty would be an inoperative cruise control.
My neighbor had a similar truck and similar problem. Take a look above the right rear wheel for a PCB mounted on the inner wheel well. It controls rear lights. It is not protected and may be covered with mud. Contacts on the board will be rusted and corroded.
Could also be the turn signal switch, when you put the turn signal on it disconnects the brake light from that side. The bulbs use the same filaments, although usually both sides don't go at once.
If it were just the brakes, I'd say the brake switch.. GM actually had recalls on those for many trucks in the mid-2000's..
But.. That would only cause the brake lights not to work.. Wouldn't affect turn signals.
You are on the right track. The taillights' lightbulbs have two electrical contacts (usually two beads of soft-lead contacts). One of the contacts receives power, and that happens when the brake pedal is pressed. The brake switch should be somewhere up above the pedal, right next to the arm.
The brake lights should come on whenever the brake pedal is pressed, regardless if the ignition switch is on or off. For the following test, don't put the key on the ignition, nor turn the lights ON:
a. Have someone press the brake pedal and see if the brake lights come on
b. If they don't, remove the lightbulbs and make sure that you have installed the correct ones for your vehicle. These lightbulbs must have two soft-lead contacts at the base. Also, just because the lightbulbs have two contacts, it does not mean that they are the correct one for your vehicle.
c. Check the brake switch. There always is power at the side of the switch closest to the fuse, and this power is transferred to the other side, only when the brake pedal is pressed.
Lastly, for the OP: if you don't know how to troubleshoot electrical problems on your automobile, by all means have the right person taking care of it for you. It's better being safe than sorry
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