So here's my issue (I hope I'm posting this in the right place): I have a 2008 Scion xB with numerous modifications, but very little done under the hood. The only things that I believe could be relevant to the issues I'm having are remote start, aftermarket stereo, aftermarket headlights, and (since uninstalled) bluetooth.

I have no problems with starting or driving the car, remote start or with the key. When driving and the headlights are off, when I turn on my turn signal, the entire instrument cluster blinks with the frequency of the turn signal. The aftermarket head unit will also flash in the same way. If I turn the rheostat all the way up and click it into the highest setting, the issue will go away when the headlights are on.

I ordered a new rheostat, thinking that was the issue, however I noticed no change after switching the parts out. This issue predated the installation of my stereo, so I'm sure I can rule that out. I'm not really sure what else I can check at this point. Can someone point me in the right direction?