ok, so I started working on my 86 K30 truck that's been sitting forgotten about for the last 6 months... there was something wrong with the rigged lights it had, so I just parked it... today I got some all new lights going : one pair of nice backup lights, and one pair of dual-function red lights (dim and bright), wired them all correctly (I think) with a new trailer-lights harness as well...

everything looks nice and seems to kinda work on the rear end of the truck... I get the taillights ok, and the blinkers work ok, but the brake ligths don't light up... seems like since both bright and dim functions work (tail and turn), then brakes should work too (like both turn's on at the same time)...

I even unplugged the switch by the brake pedal and manually bridged the 2 contacts with a piece of wire, still no brake lights, so switch is prolly ok... seems like the problem must be somewhere in between... is there a separate fuse? (labels on my fuse box are all worn out) or is there some little gizmo that decides to switch both turn-signal lights on to indicate brakes? bad ground? anything else I am missing?

:think:

The brake light circuit is somewhat complex, in that it goes through the turn signal switch and then to the stop/turn bulbs. The power for the stop/turn circuit has one fuse. Power goes through the stoplight switch to the turn signal switch where the internal contacts send it to the proper bulb filament.

If the switch is in the "left turn" position, power for the left side bulb filaments goes through the flasher before it goes to the bulbs, as directed by the internal contacts inside the turn signal switch. At the same time, if the stoplight switch is activated by applying the brakes, the power for the stoplights goes through the turn signal switch, it finds the contact to the left rear bulb is "being used" but the contact for the right rear bulb is "ok", so current is sent to the right rear stop/turn bulb. You now have the left bulb blinking through the flasher and the right rear bulb on continuously, through the stop light switch.

Like I said, complicated. Using a test light, check for power to the switch, one wire (.8 orange) should be "hot" all the time. The other (.8 white) wire goes to the turn signal harness plug. When the switch is activated, the white wire should show power at the turn signal connector. If so, problem is in the turn signal switch itself.

thanks Fred, this will get me started for today... I will play around with it and post the results :)

maby you could start at the brake light switch down at the brake pedal

see if your emergency flasher is on

If the four-ways are on the brake lights still work

ok, so I got power to the orange wire on the brake switch, and when I bridge it I obviously got power to the white one also (measured ok), still no stoplights...

since someone mentioned the hazards switch I though what the hell, and surprisingly noticed something weird... with brake switch off (wire not bridged) the hazards don't work at all, but with brake switch on (wire bridged) the front indicator ligts are on continuously and still nothing on the rear... I wonder if the problem could indeed be related to the hazard light switch and how hard it is to get to... or is there a possibility that the hazard switch does not work right because of a part of the turn signal switch malfunctioning??? also, I wonder how hard the turn indicator switch is to get to, and what it takes to replace it, if that's what I need to do... anything to test before I disassemble everything and create yet another project???

check your ground connections

would anyone happen to have a wiring diagram for this circuit???

this is easy, use a multimeter of circuit tester of a power probe, go to the brake light switch, it is by the brake pedal, it has a button on it that the pedal pushes when released, check to see that you have power going into the switch, and check if you have power out of the switch when you push the brake pedal

ILYA, you have a PM waiting, Fred

thanks again, Fred :)

this is easy, use a multimeter of circuit tester of a power probe, go to the brake light switch, it is by the brake pedal, it has a button on it that the pedal pushes when released, check to see that you have power going into the switch, and check if you have power out of the switch when you push the brake pedal

ditto :cool:

ok, so I got power to the orange wire on the brake switch, and when I bridge it I obviously got power to the white one also (measured ok), still no stoplights...

since someone mentioned the hazards switch I though what the hell, and surprisingly noticed something weird... with brake switch off (wire not bridged) the hazards don't work at all, but with brake switch on (wire bridged) the front indicator ligts are on continuously and still nothing on the rear... I wonder if the problem could indeed be related to the hazard light switch and how hard it is to get to... or is there a possibility that the hazard switch does not work right because of a part of the turn signal switch malfunctioning??? also, I wonder how hard the turn indicator switch is to get to, and what it takes to replace it, if that's what I need to do... anything to test before I disassemble everything and create yet another project???

still curious as to what it could be