1992 GMC C1500. Drivers side blinker/brake/hazard light don't work.replaced bulbs. plugged taillight assembly into opposite side and it works so it isn't anything in the taillight assembly. ???????

Try replacing the flasher relay they are relatively inexpensive . It controls the blinking as in hazards and blinkers

ck fuse for rear taillights tis under the dash lower left of steering wheel. or if you still have the manual look in there under fuses.
also look for a bad ground but i doubt that.. if it's both rear out.
fast flashing well here's a chart with all sorts of info.
Problem What To Do Turn signals light, but do not flash Replace the flasher No turn signals light on either side Check the fuse. Replace if defective.
Check the flasher by substitution.
Check for open circuit, short circuit or poor ground. Both turn signals on one side don't work Check for bad bulbs.
Check for bad ground In both housings. One turn signal light on one side doesn't work Check and/or replace bulb.
Check for corrosion in socket. Clean contacts.
Check for poor ground at socket. Turn signal flashes too fast or too slow Check any bulb on the side flashing too fast. A heavy-duty bulb is probably installed In place of a regular bulb
Check the bulb flashing too slow. A standard bulb was probably installed in place of a heavy-duty bulb
Check for loose connections or corrosion at the bulb socket Indicator lights don't work in either direction Check If the turn signals are working
Check the dash indicator lights
Check the flasher by substitution One Indicator light doesn't light On systems with 1 dash indicator:
- See if the lights work on the same side. Often the filaments have been reversed In systems combining stoplights with taillights and turn signals
- Check the flasher by substitution On systems with 2 Indicators:
- Check the bulbs on the same side
- Check the indicator light bulb
- Check the flasher by substitution
hope this helps. may want to print for future reference. :)
hope this helps.

I'd be willing to bet your dash lights don't work either when you turn the headlight on.change the headlight switch, it has a short, it's only about 11 dollars at advance auto, and is fairly easy to replace. my 93 chevy did same thing, changed headlight switch, problem solved

I've got the same problem on 98 GMC Sierra.

I'm an electrical engineer, I checked the electrical diagrams and verified that there is no problem in the rear lamp assembly or wiring. With the light assembly unplugged, I can actually watch the blinker and brake signals operate with a voltmeter. The Tail light works OK.

It simply won't provide enough current to light the bulbs.

I'm afraid that it's melted one of a pair of normally closed contacts inside the blinker switch that feed the brake and turn separately on each side.

if your fuse is good. and you have power at the brake light switch and when you hit the brakes you have power coming out the otherside of brake light switch/which would be the white wire/ check that the white wire is sending power up the turn signal switch. if theres power there and your turnsignals work? im afraid that your turnsignal switch is bad rare but it has been known to happen.

what you have is a bad ground to the taillight units, first thing to check

Do the brake lights share the same bulb as the turn signals? If so the brake light circuit goes through the turn signal switch inside the steering column. There could be an open in one of the wires or a contact in the switch causing the brake lights to not work.

I have notice that this is a common problem. The socket most of the time goes bad, I don't know why but they just do. You can pick them up at any parts store for around 5.00 each. If you don't have a volt meter and ground straps to test it right, then I would try changing the sockets out. Quick and easy. Let us know how it goes.

TEST FRONT RIGHT BLINKER CIRCUIT AND REPLACE THE BULB,,WITH PROPER BULB...A DOUBLE CIRCUIT BULB IN A SINGLE SOCKET WILL DO THAT ALSO A SINGLE SOCKET BULB IN A DOUBLE SOCKET HOLDER....CHECK LEFT SIDE BULB FOR ACURANCY

That's an issue with wiring somewhere alont the line. There has to be a short somewhere. Hopefully for you the short is from the new taillight assembly being installed and it would be relatively easy to get to. Hope it helps!