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Turn Signal Blinking Very Rapidly

I have a 2002 Cavalier with 140K miles. I recently noticed the left turn signal on the instrument panel flashes very rapidly when I flip it on. The front exterior blinker also flashes very rapidly. The back left blinker is not working at all now but the brake lights back there seem to be working fine. Any ideas?

the left rear bulb is bad. change it

There is a short circuit in the turn signal wire leading to the L/R bulb…The short might be in the bulb or bulb socket or anywhere along the wire…

No, there is no short circuit. In the old days, that would be true. But today, the electronic flasher flash at double speed when one or more of the bulbs is burned out. This is on purpose to let you know that a bulb is out.

The bulb flashes fast due to a amperage change in the circuit and it does it in cars equipped with standard bi-metallic flashers.

With the old bi-metallic flashers, excess current (like a short) would cause them to cycle rapidly. Less current (such as a bulb out) would cause them to cycle slowly or not at all. The newer flashes (which the OP’s car has) are electronic. They use an electronic timing circuit and a relay to flash the bulbs. This electronic circuit also has a current sensor built in. Current is sensed by measuring the voltage drop across a copper trace on the PCB designed to work as a resistor. A series of OpAmps makes this same voltage change readable. A comparator alters the timing circuit to be a double speed if the current sensed is too low.
If you are going to give advice on modern cars, please learn how stuff works before posting.

My text does list a condition with a bi-metallic flasher flashing to fast,it does say check bulbs first.

Also listed is a flasher a you describe,I did not have a schematic to verify the Cavalier had a electronic flasher,I relied on memory as to the flasher type.

I do make a effort to verify,some things slip through.

Usually it is a bulb burned out, and you said the left rear signal was not working.