When the headlights are on the front left turn signal doesn't work. When the headlights are off both turn signals work. Any ideas? My mechanic said he thinks it's the control box and quoted about $500 used and $1000 to replace it. Any second thoughts on that? Rear turn signals work either way. Thanks.

 

Was the bulb changed? The feed for the signal is fed from the BCM and goes through the PDC on it's way to the front bulb. I am assuming wiring issue and the dimmer filament is the one flashing when the lights are off. So when the lights are on, the other power overrules the signal input. But just a guess.

 

Just for grins disconnect the negative battery cable for 5 minutes then reconnect. This will reset the data bus and components on it like the BCM and FCM which control headlight and turn signal functions. Long shot but easy to do. If it comes to it both of those components can be had for less that $500. The FCM is an easy change. The BCM is a bit harder but doable. As stated, the wiring needs a thorough going over first.

 

The mechanic put in a new bulb, but it didn't make a difference. I disconnected the negative battery cable for five minutes per suggestion, but issue is still there. Left turn signal is fast whether headlights are on or not. I'll have the wiring checked next and let you know what we figure out. Power locks haven't worked for a while either, even with fuse replaced. Thanks for the input.