I feel kind of dumb, however I have a 1972 cutlass supreme convertible. When I hit the brakes, the front parking lights turn on also. Any thoughts are appreciated.

 

Grounds.
Chase down the light harness grounds.
The other grounds will need attention too. Its a 54 year old car. All other grounds need the same attention.

 

Check for ground problems at the TAILLIGHT sockets. There is no electrical connection from the brake light circuit to the FRONT light sockets under normal conditions. If the rear tail light sockets have bad grounds, the brake light circuit will ground through the park light circuit, which DOES have a connection to the front sockets. That is the only way for the brake circuit to apply current to the front park lamps.

 

Is it possible that single contact bulbs have been installed in the stop lamp sockets?

 

Ding Ding Ding! If a single element (1156) light bulb is installed in the brake light socket instead of a dual element (1157), the brakes and turn signals will feed power into the parking light circuit.

 

Someone brings this up every time. I have to say that in over 50 years of working on these cars, I've never seen this done. One has to be pretty clueless to force an 1156 into an 1157 socket. The bayonet pins are not in the same locations and you really have to jam it into place. Can it be done? Yeah, but if one is that clueless and unable to sense the fact that the bulb is being forced into the socket incorrectly, I shudder to think what else is screwed up on that car. Far more likely is a bad ground at the tail light sockets, which will cause the same effect. Also, if the contacts inside the socket are damaged or spring out of position, this can also cause cross-shorting between the two circuits.

 

Yo Joe! I love saying that. Reminds me of Saturday morning cartoons. Yes I know the bulbs should not be able to cross polinate, but I had many, many customers come back to the stereo shop claiming "it didn't do this before!" They would spend a little cash on a new stereo for their new-used vehicle, change a few bulbs to make all the lights work and somehow manage to crank 1156 bulbs into the brake light sockets. Some of them would still argue the point even after I showed them the difference. It happens way more than you I would imagine.

 

In my forty seven years I've seen it more than once. For an inexperienced DYI apparently it's not as difficult to do as you think. The first time I saw it was when a "experienced" mackanic literally had the entire dash wire harness and steering column pulled apart on a mid seventies Econoline Van. The shop owners cousin (not a mechanic) looks at the mess, asks why the vehicle is disassembled and states oh I had the same problem on my ______ and it was the wrong bulbs in the taillights. After three days of hair pulling the problem was solved in thirty seconds. I'm not saying this has to be it but it is worth mentioning. Never say never.

 

Joe P. You may find it hard to believe that there are clueless people. But "THEY DO WALK AMONG US".

 

And they reproduce...
I know I have done my share of stoopud things.

 

I DO NOT think Joe has a hard time believing the clueless hold a strong majority in our society.
🤣

 

It's not as hard as you think with some of these offbrand bulbs.