We have a 1994 2wd Toyota pickup truck. Sometimes the left turn signal blinks fast. The rear bulb lights, but the front one doesn’t. We put a new bulb in but it didn’t change things. I decided to troubleshoot it this afternoon by turning the blinker on and crawling under the front of the truck to check the wiring and connections. Between the time I turned the turn signal on and the time it took to get to the front of the truck (just a second or two) the blinking went back to normal and the front bulb lit as it should.
Any ideas on what to check next will be appreciated.
When i had the very same problem on my 95 Taurus a quick look at the wiring diagrams told me that the only difference between the turn signals & emergency flashers was in the turn signal/flasher switch.
My flashers worked fine. Replaced the switch & problem solved.
Does your Toyota also have the combined switch?
Check the ground connection to the front turn signal light. Also, inspect that bulb socket closely. Alternately, it could be the turn signal switch. If you jiggle it, does it make it start or stop working correctly?
You may want to try replacing the two rear lamps. It is possible, in many cars, for a lamp to fail in a way that will cause this issue. Simply replacing the lamp corrects it. It is a result of one filament sagging and touching the other one in the lamp.