try replacing the blinker under the dash that little box that makes the blinker sound
turn signal relay fuse
An open ground or a short to ground when the signal is on. Usually a bad bulb.
Check all of your turn signal bulbs. One of them may be burned out.
POSSIBLY A BADGROUND
your rear bulb is blown - replace the bulb The turn signal blinks fast because the bulb is going out. That is also why the others dont blink.
turn signal relay is bad
Generally, a change in turn signal blink rate is an indication of a burned out bulb. Depending on the manufacturer's design, some circuits will speed up, and some will slow down, when the current load is reduced.
Buy a "highway" turn signal flasher
Incorrect size bulb installed.
Check your bulbs and your flasher.
Probably needs a fuse.
This may very well be a problem with your ground connections at that turn signal.