no key in step on brakes, headlights go up, and when parking lights are on head lights on or off the taillights have both elements lit up in the taillights like the brakes are on?

1990 PONTIAC FIREBIRD
86,000 MILES • 5.7L • V8 • RWD • MANUAL
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GERALD TWARDZIK
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Okay, no key in step on brakes, headlights go up, same with key on running. Second question: when parking lights are on head lights on or off the taillights have both elements lit up in the taillights like the brakes are on, i checked all bulbs and sockets. I replaced brake switch and headlight and parking light switch. Help please!
May 3, 2017 at 8:08 PM
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CARADIODOC
  • ASE Certified Mechanic
  • 34,321 POSTS
  • ASE Certified Mechanic
For the second part, two filaments lit up is the classic sign of a bad ground. To verify that, if you have the older 1157 bulbs with the brass base, measure the voltage on the base. You should find 0 volts. If the ground is bad, you will find some voltage; most commonly around 6.0 volts.

I get the impression you have hidden head lights, and those open when the brake lights turn on. Most likely the relays are seeing the voltage on the taillight circuit and are operating in response.
May 3, 2017 at 9:02 PM
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