The only problem I'm having with my 72 Malibu is that the brake lights do not activate when I apply the pedal. All the other lights in the car operate properly as far as headlights, tail lights, hazard lights, turn signals, reverse lights and so on. Just the brake lights refuse to work when the pedal is put down. I had it checked out by a mechanic that said the brake switch at the pedal is working fine. The fuses are all intact with no problem. I checked the voltages at the wiring harness in the trunk and everything has read normal. Is there anything specific between the brake switch and the rear harness that typically goes out causing the problem? Could it be the flasher? My friends and I are mystified at this point. Any feedback is appreciated. Jeremy J.

With the turn signal in the off position do the following:
1, Push down on the brake and measure the orange wire on the brake switch to ground. You should have 12 volts. If you see 12 volts then measure the white wire to ground on the brake switch. It also should have 12 volts.
2, If you do NOT see 12 volts to ground on the orange wire, release the brake and measure it with the brake off. See if the 12 volts starts appearing with the brake off.
3, If you see 12 volts on both the orange and the white, push the pedal back down and measure these wires to ground on the large turn signal connector.
White
Green
Yellow
You should have 12 volts to ground on each of those wires with the brake on.
Post back the results and we'll see which way to go from there.

replace the brakelight switch under the dash. they are cheap. had the same trouble, that cured it. like 8 bucks

To WestyJ69chevelle: Did your faulty brakelight switch still have voltage going to it by chance? We found out that mine still has voltage running to it as if it's still working properly when the pedal is applied. In any case, 8 bucks to get a new one may be worth it no matter what if there's the chance that it'll rid me of the problem.

To John: I'll definitely take those measurements. A friend and I did go through taking most of the readings once before, but its been a few weeks since we did that. I did finally manage to get a wiring diagram for the car and I'll follow through with your suggestion.

yup it did. the prob is, you cant really tell if its bad or good, just by looking at it. if its no good inside, I dont think there is a way to tell.

Originally posted by WestyJ69chevelle:
yup it did. the prob is, you cant really tell if its bad or good, just by looking at it. if its no good inside, I dont think there is a way to tell. Sure there is, by checking "voltage" like John said above.

forgive my inexperienced ignorance.. graemlins/clonk.gif still a newbie to the High perf world,, but hey at least I am not one of the cut coils and a fart pipe kids

Guys as a Dealership mechanic of many years I can tell you with great confidence that you have a bad contact in your turn signal switch in the Column. As you have the switch set to a perticular side it has to cancel the brake light to that side, so your brake lights pass through the Turn signal switch. I have seen this problem MANY times and most people will not believe me when I say replace the turn signal switch, then after replacing every other part in the system the switch will get replaced fixing the problem. Just check the brake light fuse and brake light switch first, check the brake light switch a 12 volt test light, you should have power on one terminal all the time, if not the fuse is blow or the wire is broken between the fuse block and the switch. The other terminal should get hot when brake light depressed. If you pass this test and the turn signal works normal then u have a bad trun signal switch....trust me :D

I'm guessing dirty fuse clips on the brake fuse. Should have mentioned to do the testing with the bulbs installed.
Now if I could only guess those Lotto numbers...

Sorry for not replying back for so long. My cars in storage and I can usually only get up there during the weekends to check things out.

Went through and replaced the brake light switch, but the problem is still there. Another problem recently found when my brother and I went through is that the rear hazzard lights will not flash now. They flash in the front, but not in the rear. So now my both my brake lights and rear hazzard lights are inoperable. I believed the hazzard lights were working in full last time I was up there so I'm hoping I didn't wreck something further. I apologize for any inconvenience in not revealing this sooner. In response to John_Muha in measuring the voltages everything seems to pass. To Q-Ship, we dismantled the steering column and checked the contacts and everything looked perfect and the fuses checked good. So at this point I'm about ready to fish for someone who can service the car before the snow flies. If anyone has any further suggestions I would appreciate it. Sorry again for the reply time. Thanks guys. Jeremy.

Did you happen to measure the green and yellow further down? That is did you measure them at the rear bulbs or at the connector inside the trunk.
You do have 1157 bulbs in the rear?
I've had one bad rear socket act up but haven't seen both go out at the same time. Might be the problem.

Not sure on '72 but my '69 had corrosion where the bulbs snapped into the tail lamp housings. Cleaned up sockets and mounting points, fixed mine.

Starting in 71 the sockets have a third wire and don't use frame ground.

See there, I learned one more thing today.... Thanks John. smile.gif

To John_Muha, we measured voltages off the green and yellow wire up to the connector in the back. we figured that since all of the other lights operated fine past that connector that the problem resides somewhere further towards the front end. We did remove the drivers side rear bulb to inspect it for defects, but it checked out as being good and the correct type. I was given another suggestion from a friend of mine that the relay switch where all the lighting wires come together at the dash could be bad. Do you know the exact location underneath the dash where this relay is located? I'll check thoes bulb fixtures again to make sure there's nothing loose back there. Please reply back when you can. Thanks. Jeremy J.

There is no relay.
Next time you get a chance to measure things try this.
With both the rear bulbs installed, measure the green and yellow wires on the trunk connector to ground. Someone needs to push down on the brake pedel. You should have, again, 12 volts on each one.
If neither brake light comes on, remove the screws from one of the tail light lenses. With one end of a jumper wire, touch the light bulb metal base right where it meets the glass. Touch the other end of the jumper to a clean good ground. Do this while someone presses the brake. See if the brake light comes on.

I know you said the contacts in the switch looked good but it is the turn signal switch, if the front hazards work but no rears and brake lights just confirm the bad switch to me. Replace the swtich and the problem will disappear.