I know this sounds like a silly question but here we go. I have a 72 Cutlass and am curious about the operation of the hazard lights. Mine operate and all 4 flash accordingly however when you apply the brakes they stop flashing and all 4 lights go solid. Is this normal operation or do I have something wrong? I took a look in my CSM and only found wiring diagrams and diagnostic chart if they were fully inoperable. Thanks in advance for any knowledge on this topic!

 

It's working as designed. Took GM a little longer to engineer four-ways to still flash when the brake was applied.

 

That's what I thought I remembered but wanted to double check. Thank you!

 

The four way flashers use the same filaments as do the brake lights. When you press on the brake pedal, it applies power to those same filaments in parallel to the power applied through the hazard flasher module. Since there is power applied full time in addition to power applied through a flasher, the brake light circuit takes priority and the lights stay on. Since the hazard switch connects all four corners together, the fronts also stay on in addition to the rears. Normally you'd use the hazard flashers when the car was disabled on the side of the road, so this really wasn't an issue for design of the circuit.

 

Joe, thanks for the explanation. Learning something new on this old stuff everyday!