Light socket has no voltage, switch check s out fine

Check for battery voltage at head light socket , if voltage replace bulb, if no voltage check voltage at light side of relay if ok check wiring to lights, if no voltage check switch side of relay if voltage replace relay, if no voltage check voltage at head light switch , both to and from switch, if faulty replace.

Does bulb socket have a ground wire, or just uses mounting point as ground? Check for voltage at each part of system. Start with fuse, then switch both in and out of reverse, then bulb.

Check the ground with an ohm meter.

Depending on the age of your vehicle you may have a problem with the bulb sockets. I am assuming that you have checked the bulbs. Remove the bulbs and check for voltage in the bulb sockets with the brake pedal depressed. If there is no power then you may have to do some wire tracing looking to see if the wires have been pinched or cut by something.

Back up lamps, Use a test light and check voltage and ground. Check voltage at fuse also, using the test light. As you can see, the back up lamps are wired through the neutral switch. At the back up lamp socket, the light green wire is voltage and black wire is ground, check them both.

check all fuses using a test light or volt meter if they are all good test for voltage at brake light connection if you have voltage in and out of switch test for voltage at rear light sockets with someone holding foot on brakes if voltage is present replace bulb or socket if no voltage is present a wire between switch and socket is broke . but that is very rare.a fuse is usually the problem dont just visually inspect them

it could be the turn signal switch, voltage goes from the brake light switch to the turn signal then to the taillights, use a test light and follow the circuit from the pedat to the sockets, also check the grounds

take a volt meter to the sockets and see if you get any voltage. if you don't, try a continuity test on the socket and see if there are any shorts, blown fuses are good indications of shorts. if you have no voltage and no shorts, you have cut wires somewhere along the lines. i'd say check your relays but if your not getting any voltage at all, it probably won't be relays. check it anyway
hope it helps

If the brake light switch is bad, both brake lights would be out, so don't change it. Check the brake light socket to see if there is any corrosion inside, which is usually the problem. Use a piece of sandpaper folded over and push back and forth with a small screwdriver to clean up contact in socket. To prevent corrosion in the future, pick up some dielectric grease at any parts store, and place a bit in the socket. If corrosion isn't the problem, you need to check the socket with a voltage meter to see if there is power to the socket when brakes are applied. If not, you will have to trace wires back to find where the problem is.

First, I'd check voltage at brake light socket terminals. voltage should be the same or slightly lower than running voltage recommendation of about 13.5. (check running volts at battery with engine running. check brake light volts again with engine running, using the bulb terminal and socket as power source and ground.) If voltage is excessively high, I'd look at the charging system to find out why. If volts at battery are normal but volts at socket are low, I'd suspect a bad ground in the lighting circut, causing excessive resistance & heat, causing sockets to melt. If this is the case, re-ground both light sockets to a good ground source such as the chassis. (when attaching, scrape off paint, rust etc to insure good connection.