Left signal light sometime work sometime not - 1999 Plymouth Voyager

because of no light flasher on left side the front one will go faster .maybe the left rear light is burn. and brake lights are control by the brake switch on brake pedal hardware, might be unadjust

I would start at the left brake light. Check the bulb and wiring. Your brake light could be grounding through the blinker circuit.

Has the car been in a fender bender ? check for wiring going to the front and rear lights to see if on has rubbed into a ground wire or the body. ( even if there has been no accident.)

check the elements in the light bulbs sometimes they short together

I recommend that you change the relay of the signal light or check the wire of the left signal light.Iin some cases you can find water inside of the signal light case, .

possibly flasher unit faulty
or turn signal switch

Sound like the turn signal switch is bad,also check the harness if you have an aftemarket tow hitch.

It seems you have an electrical short somewhere. Unfortunately these are not easy to diagnose. Look for any broken or frayed wiring. With the lights on, flex the wiring harness in and around the areas that connect to each light to see if you can make the light go on and off.

any increase in bink speed is direcly related to a bulb being burt out.

check your left light fixture.make sure you have a good contact.sometimes they burnout