Will bad flasher stop left from working and not right?

Yes, a malfunctioning flasher can affect the turn signal operation on one side of the vehicle. If the flasher is specifically designed to control both left and right signals, a failure in the flasher can prevent the left turn signal from working while potentially allowing the right to function normally. However, if the issue is related to wiring or the turn signal switch itself, it could affect both sides differently. It's important to diagnose the specific cause to determine the exact issue.