I have no signal lights - 1991 Pontiac Grand Am

There are a few possible reasons why your turn signal light is not working while your brake and tail lights are functioning properly:

1. Blown fuse: The turn signal lights are connected to a different fuse than the brake and tail lights. The fuse for the turn signals may have blown and needs to be replaced.
2. Turn signal switch: The turn signal switch, located on the steering column, could be malfunctioning and needs to be replaced.
3. Wiring issue: A wiring issue, such as a broken wire or loose connection, could be preventing power from reaching the turn signal lights.
4. Flasher relay: The flasher relay is responsible for controlling the turn signal lights. A faulty flasher relay could be preventing the turn signals from working.
5. Signal/light module: Some cars have a signal/light module that controls the turn signals, this could be faulty and need to be replaced.

there is a short in the turn signal socket, take the turn signal light off and try if the dash will flush when you use the turn signal, i see this problem with Hyundai.
make sure the turn signal socket tide and touch both clips

The high mount brake light gets its own signal from the brake light switch (on the brake pedal). Or at least the wire leaving the brake light switch will splice, one wire to the high mount brake light, and the other for the rear brake lights is routed through the turn signal switch, and coordinated there with the turn signal wires to the rear brake lights. The brake wires and turn signal wires share the same wire, and same filament in the bulbs. It is kind of complicated, but brakes applied with no turn signal, brake light wire goes from brake light switch through the turn switch and out to the bulbs. If brakes applied with turning signal, non blinking brake light wire goes from turn switch to rear light, while the turning signal wire will go through the flasher relay, and then to the rear light to cause blinking.

I hope that makes sense. It appears the problem may be in the turn signal switch for both the turn signals and the rear brake lights.

Turn the parking light and compare the brightness on all lights. Next turn the flasher and compare the brightness on all light. Some time light bulb like 1157 will be insert the wrong way and short the light to signal. second open the light socket remove the bulb and inspect for burn mark and rust(replace the socket.
Behind the carpet is the ground point, clean and tight the ground.
and last is the combination switch for light and signals.
Good Luck

it's the grounds if they're both flashing fast it's definitely grounds take a test light and see if its got power goes through the test light grounded to the frame and if the light comes on then it's definitely your grounds

Fuse sure didn't play, bulb is unlikely to be all bad. Check the turn signal switch, first find the turn signal switch plug, put the key to ON file, in trying to find a turn signal lamp switch wire (flash to the thread) will this wire with no light ON one side of the turn signal line connected to see if a turn signal light, the light is turn signal switch is broken, or the plug contact undesirable, don't light it is turn signal switch to light ON one side of the light path, in order to determine whether the light bulb is broken can open a small lamp or led brake lights to borrow their wire leads to a turn signal whether turn signal light, so you can determine whether the light bulb not bright side is broken.auto diagnostic tool.

my oldsmobile 1995 cutlass supreme has the same problem, so I replaced turn signal switch.

You have to check the wiring of your signal lights. Start
at the signal light switch mounted at the steering column. Then, at the fusebox for shorted or melted terminal. Finally, at the signal light sockets, by taking off the signal light lens.

You have a short to power somewhere in the wiring harness. (most likely) Check your wiring for chafed wires that are touching.

Igot the same problem on left side.The problem was the convertor for the trailler plug.