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gomi_otaku, Technician
Category: UK Car
Satisfied Customers: 3457
Experience:  VW Technician, VW FastTrack, VW Academy, VW Certified
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When idling at lights the headlights flicker like the engine

Customer Question

Hi - when idling at lights the headlights flicker like the engine is about to stall
JA: Have you checked the fuses? Have you checked the bulbs?
Customer: Don't think it's the lights - think it's more like the engine almost stalling - the lights seem to dim and the go back to normal brightness.
JA: What is the make/model/year of your car?
Customer: Mazda3 2011 1.6
JA: Are you fixing your Mazda3 yourself? What have you tried so far?
Customer: No - will take it to the garage but will not be until next week but don't want it to break down on me.
JA: Anything else you want the mechanic to know before I connect you?
Customer: No
Submitted: 9 months ago.
Category: UK Car
Expert:  gomi_otaku replied 9 months ago.

Does the engine change RPM at all? It's pretty typical to be able to watch your lights on the bumper of the car in front of you, dim and then brighten again, as the charging system is most efficient at a higher rpm. If your car actually drops idle as if it is going to die, then I would suspect an engine issue (like a vacuum leak in the intake hoses) but otherwise it is relatively normal operation of the lights and charging system. You could always test the amperage output of the alternator, and load test your battery. Most shops will have a tool that can do this just by hooking up to the battery and testing both.