[David Krogh]

All of a sudden, the brake lights went out on my 1972 Pontiac Lux LeMans. I have tried a new relay, new bulbs, and checked the ground and nothing works. Does anyone have any ideas?

Thanks

[Bryan59EC]

I think the brake lights and the tail lights are on the same fuse.
Check that fuse.
If you have working tail lights -- could be a bad brake light switch.

And getting to worse scenarios---could be in the turn sig switch

Do you have signal lights??

Brake light switch is easy to get to & cheap to replace if necessary.

Check for voltage on both sides of the brake switch with the brake pedal depressed

Have you checked for a short--check for one if you have a blown fuse.

Bryan

[docvette]

Doc here,

First we assume, you have checked all the rear grounds..and they were good..If not, that is where to start.

As Bryan Said, Check the fuses going aft..Brake lamp and Tail lamp Fuses..These are usually separate feeds, and some tails are wired to the Instr Lamps (So you have a Visual reference when the tails are out, before someone plows into you)

Check the brake lamp fuse, It usually is a lone connection.

If tails DO work but stops are dead..Pull both wires from the brake lamp switch, and jump them together and check the brake lamps..If they light..you need to replace OR adjust the brake lamp switch..

If they don't , Get a DVOM, set it for DCV, V X 50 or autorange, and measure BOTH sides of the wires, ONE should have 12 volts on it..If not..backtrack the wire from the fuse panel BRK LMPS to the Switch, I think you'll Find it's open.

If it does have power, remove Bulbs, and check CONTINUITY, between the dead wire at the brake lamp switch, and the lamp socket (s) in the back..Using your DVOM set for Continuity , or OHMS scale, R X 1, Calibrated 000, and a long jumper..With no Turn-signals selected, it should read 000 at the high (brighter ) Filament, at each bucket..If not move back to the column plug at the bottom of the column.

Get a Schematic for your car, pull and inspect the plug at the bottom of the column , Clean and burnish the pins and be sure it wasn't loose when you pulled it. Next Isolate the brake lamp wires in and out of the column..measure the wires from the fuse to the left rear and right rear pins on the COLUMN side, for continuity..With no signal selected It should read 000, between the power (brake lamp switch) and the pins going back to the lamp buckets..

If not..you need to pull and inspect and repair/replace the turnsignal switch and column harness as needed..

The same procedure applies to the turnsignal troubleshooting procedure, except you move your test to the Flasher and rear light pins AND select the side your testing at the signal switch.

If the Whole Rear is dark..Check the harness going to the Rear down the Drivers side wire trough..

Pay special attention to the area where it crosses out of the body and under the carpet and under the rear seat..

Also inspect all the wires in the trunk. a loose jack can slice a harness in two.

That should get you started..

Let us know what you find

Doc

[jimfulco]

If the brake light switch is the plunger-style, make sure the plunger is not sticking. While you're there, wiggle the connector in case the connection has some corrosion starting.