I have a 1998 379 Peterbilt I don't have any brake lights, no turn signals, no 4 ways, doesn't even light up on the dash. Can't find any fuses blown

Turn signal and brake lights operate from a different switch. The brake light switch is under the dash behind the brake pedal. Look under the dash and follow the brake pedal up until you see a switch which the pedal operates. Normally a white plastic switch with two wires. Disconnect the two wires and touch them together. If brake lights come on replace the switch. If not use a 12 volt test light to see if there is current to one of the wires. If not, check for a blown fuse. This should solve your problem. If not, contact me for further information,

Sounds as if the bulbs are bad, but could also be a failed multi-purpose switch.

yes ,
check the fuses.

sounds like the relay is hosed. Turn on right blinker and follow the blinker sound under the dash, usually. Usually the other relay will be right next to it. The relay turns the voltage on and off to make it blink

Have yoiu changed/checled the lightbulbs? (In other words,do your turn signal lights work? If the front turn signal lights work, but the rear don't, then turn on your four (4) way flashers. If the rear lights still don't work, then all the bulbs are bad. It is rare for all the bulbs to be burnt out at the same time, but it does happen.

If the turn signal/four way flasher lights work, then you probably have a bad brake light switch. However, first check your owner's manual to make certain there is not a separate fuse for these lights. If there is, then swap the fuse for the brake lights for another fuse (or relay) of the same size/amperage. (Facing the hood, the power relay box is located on the right side (usually) under the hood.)

The fuse box is located under the dash, on the driver's side of the car. Usually there is a plastic cover that has to be removed to access the underside of the dash, and then there is a plastic cover that has to be removed to access the fuse box. If you don't have an owner's manual, nprmally the fuses and power relays are normally marked on the plastic covers your remove ot access the fuses and power relays.

If the fuses/relays are good, then you have a bad brake light switch. This is located on a bracket just above the brake pedal. When you push the pedal down, the switch makes contact. Disconnect the plug to the switch, and jump across the plug contacts (not the switch) with a small piece of wire, or if a piece of insulated wire is unavailable, you can use a paperclip, you won't get schocked, just make certain that the paperclip does not come in contact with a ground while you have it plugged in to the plug for the brake light switch.

If the lights stil dont work, check for power to the plug for the brake light switch. If you have power to the plug, the turn signals and four-way flashers work, then my guess would be that you have a broken power wire (probably iside the steering column, or a bad turn signal switch. If the brake lights work whe nyou jump out the brake light switch, then the brake light switch is defective.

Some of older cars used 2 seperate flashers one for the signals and one for the hazards.

DID YOU REPLACE THE BULBS

then it's probably a ground wire that isen't atached

The odds are the one fuse is blown for the dash and the tail lights. And the wrong bulb may have been put in for the brake light. The brake light is feeding back into the tail light circuit causing the fuse to blown out.

Change out the bulbs with OEM bulbs and replace the blown fuse. That should fix the problem.

turn signals and 4 ways or hazards and brake lights all run the same circuit. Parking lights or marker lights you probably have a blown fuse. Depending on what your vehicle is it may have seperate circuit (fuse), check all your fuses