1975Coupe

Hello All,

I've got an interesting problem for everyone. I noticed when I was putting my car away for the winter that whenever I pushed on the brakes all of the lights would come on. I mean the headlights, the dash lights, the inside lights. Any ideas if this is a common issue (X fuse is loose, or this wire is pinched) before I just start tearing through the dash?

Thanks in advance.

Easy Mike

It is not a common issue.

mysixtynine

Trying to think this through logically and I just cant get my head around it.

The only thing all those lights all have in common is the headlight switch. (brake lights not so much but they are part of a two element bulb).

I don't have a 75 wiring diagram so I cant really do any mapping.

The real puzzler is you say inside lights come on as well (which i am guessing is the courtesy lights)? Those are turned on by supplying a ground... they always have 12v ... whereas all the other lights you talk about are run by applying 12v to the circuit.
68-82 use the same Headlight switch ground strap to the back of the dash so it tells me that they all use the same ground based circuit for turning on the courtesy lights.

You didn't happen to change any bulbs lately did you? Are any of the bulbs out or not lighting when this ODDITY occurs (check them all license plate, all courtesy bulbs etc). Be specific on the brake light bulbs as they have 2 elements... I'm dreaming but it almost sounds like the element on one broke and is laying across the other and when you apply the brakes its back circuiting and lighting everything else (but again that makes NO sense for the courtesy lights).

It just doesn't make sense for the INSIDE lights to come on too.

My 69 only has two rear brake lights ... I believe later years have 4 ?

Maybe try pulling one brake light bulb at a time and see if that changes the result..... just trying to rationalize the condition.

1975Coupe

OK so finally got the car out of storage and have some clarity on the issue. When you push the brakes the headlights, dashlights, and brake lights come on. If the car is off and you push the brakes it acts like the headlight switch is on, it buzzes and all the lights come on. If you let off the brakes the lights and buzzing turn off. I got down in the footwell and it doesn't appear that any wires are pinched, so that rules out my hypothesis. So any ideas?

henrikse

I would change the headlight switch. Inexpensive and tough job but seems to be common to all.
Either that or if you have meter. Push brakes and follow the voltage to see where its coming from. There isn't anything at your fuses? like something shorting fuse to fuse

myoriginal77

It may sound odd, but pull the brake light bulbs out and check them and make sure they are OK. I had a similar issue a while ago and it turned out to be a bad bulb that the brake light filament fell on the tail light filament - Good Luck -

1975Coupe

OK so I did more troubleshooting. All the lights work individually (the brake lights, the front turn signal lights). When I push the turn signal lever up (Turning RIGHT) the front and rear blink as you would expect. When I push the turn signal level down (TURNING LEFT) both the front and rear lights barely blink, just a low luminescent flash, and it makes a different sound. If I turn all the lights on by pulling the headlight switch out all 4 lights come on. If I pull it out all the way the headlights then turn on like expected. When I push the brakes with the car off and the key out of the ignition all four of the lights come on including the dash lights and it buzzes like I've left the headlights off, even though the switch is not pulled out. If I turn on the lights by pulling the head light switch out and then push the brakes all of the lights come on BRIGHTER and it buzzes (as expected). If I push in the hazard lights button all four lights come on and the car buzzes, like I left the headlights on. So really confused by this one.

henrikse

Try one problem at a time. Without headlights right signals work so turn on left and try to get that working. Are you sure your sockets on left side are good and proper bulbs in? You can take front out first and use testlight in socket to see if it will work then put front in try test light in back same way. Do you have proper flashers fro signals and four way? Have you changed anything out in these circuits. Check all your sockets , clean them and check fround by putting test light lead on positive battery with long jumper and then touch each outside of sockets to ensure good ground

1975Coupe

Wrong bulb. LOL. So I followed your advice and went thru every light. The left brake light has an 1154? bulb in it instead of an 1157 bulb. The 1157 have two connections on the bottom and the other has only one. So it was creating a short inside the socket. I swapped the bulbs from left to right and the problem moved with the bulb. So I replaced both anyways as they were old. Now everything works. No lights/buzzing when I push the brakes with the car off. Thanks for the advice everyone.

60 SHARK