check for a short in the wiring behind the dash or somewhere in that circut I had the same problem with my camaro it turned out that over the years the harness had rubbed on the plate over the ashtray and worn through the insulation causing a short, it took many hours to find and I eventually took it in to get it looked at because I couldn't find it
It has been my experience that when the blinker comes on but the lights don't blink there is one or more bulbs burned out. If that is not the case check the flasher.
The bulb may be blown or weak,also check the flasher.
cheack the wireing
The tail lights are on a separate wiring than the blinker/brake lights. Look for a blown fuse or a broken/loose wire.
when you flip your blinker on, a relay in the circuit is activated which turns the light on and off. also, the front blinker and rear blinker usually alternate in turning off and on, so when the back is on, the front will be off, and reverse.. that's why when a bulb is out, the clicking sound in the vehicle goes faster than when both are in working order.
whats the color circuit for the blinkers an break lights?
Check for a bad ground
on blinker switch
Take the whole lens out
Press both blinker directions at the same time.