Headlights flickering off and on 1999 mustang

I wonder if all the lights flicker?

Some headlight bulbs aren't held into the reflectors as securely as others and can appear to flicker due to vibration, bumps and so forth. In this case the other lights will not flicker. A similar effect can happen when the bulb connections aren't positive.

If all the lights flicker it must be the voltage that is fluctuating due to poor wiring connections or a fluctuating charge rate/alternator performance.

dodge neons dont need headlights,they glow

Do the lights flicker when the engine is off??? Do they flicker when the engine is running??? Do they flicker when the car is in motion???
You have to take all these factors into consideration before you post, and state every thing that is involved when you want some help.

Bad plugs on the bulbs.Bad grounded lights wiring.Bad alternator ground.Bad alternator charge.Bad lights switch.Also ,the new lamps may show more sensibility in voltange change or put more pressure on a older bad wiring link.

Best guess would be corroded ground wire connections to body and maybe a bad regulator off of the alternator/generator. In that respect the power would not be constat from the charging system and the bad ground may make you lights flicker from no clean connection.

Sounds like you may have a short where the fusebox is. Take out the instrument panel and check the circuitry for black spots or and type of arcing or shorts.

daytime running lamp mudule

your switch is bad. had same problem on my 1970 mustang with the headlights flickering unless I pulled on the switch. I replaced the switch and they work fine now.

Check your relay but most of the time it's your light switch that has gone bad. The swithch heat's up after a while and then that when the flickering happens if not stop working. Good luck and hope this helps

probably not , the blub could be loose in the headlight. Replace the battery and go from there