Hello all.I have talked about this before but on my 72 olds cutlass all 4 of the rear brake lights are suppose to come but only two come on when i press the brakes.One on the left and one on the right. What do you suppose is causing this problem.I've checked all the wires and they appear to be fine.But I may have missed something that you guys may mention.

Thanks for the help in advance.

 

I'd check the harness in the trunk and see if the connections need cleaning.

You can always check the sockets for power with a voltmeter.

I don't know much about the brake light switches on those cars, but could it be possible that the wrong stop light switch was installed behind the pedal over the years?

When I replaced mine, the auto parts store didn't have a matching one to mine and i had to rig in one from a buick something or other and leave the cruise control terminal unplugged.

if your original stop light switch had 2 different spade terminals for the lights and a 1 spade connector is installed, that could be the issue

 

I'd look at the sockets and bulbs. The sockets can easily be rusty and not make contact. A good electronics shop will have contact cleaner. Then use new bulbs. The contacts on the bottom of the bulb will wear down from friction and pressure, losing contact, and a "good" bulb becomes bad.

C.J.

 

The upper and lower sockets are all wired together at the bumper harness, so the switch has nothing to do with it. There isn't much to this circuit. The only options are bad bulbs, bad sockets, bad splices in the harness, or broken wires. Get a test light or VOM and just chase the circuit. Note that there are a couple of failure modes that are not obvious. First is that the terminals on the bottom of the bulb can wear down. These are usually just blobs of soft solder and vibration can wear them down to where they don't make good contact. Try installing a new bulb. The other is that the socket itself can spread to the point that the ground sleeve on the bulb makes poor contact with the socket, particularly if there is any corrosion in the socket.

 

Problem solved.The advice you gave me joe was right. actually all of you guys helped me out.I replaced all the bulbs and used a good contact cleaner and that seemed to do the job. Thank you all

 

Thanks for the follow-up. Many times when someone asks for help we never hear the results.