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Discussion Starter · #1 ·
I've had the problem where my blower and headlights will have diminished power for a second, as if the alternator is failing, so I bought one of those cig. lighter diagnostic tools that tests the alternator output and battery charge, and the levels were good, however when I would shift, and even intermittently while idling at a light, the diag. would show power cutting out. This is when the headlights are noticeably dimming, and my blower dims for a moment. The car is a 2009 Fortwo, a 450 I believe, and has 145k on it. I bet the belt needs changing even though I looked at it from craning my neck up from under the car, but I don't hear it making noise, and I haven't had any console errors or anything else out of the ordinary.

I read a long time ago about a tension pulley or something like that which kicks in when shifting, and alternator brushes or bushings potentially being the culprit.
 

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Discussion Starter · #3 ·
Thank you. I've fixed some easy things on this car already, and hope to keep it going for a long time. Hopefully this community will help, and I can be an SME.
 

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Load test your battery.
Mine was failing load test and caused the headlights to dim and blower to slow some at idle.
Also noticed the shifts was laggy.
New battery cured it.
Most parts places can check it and the alternator to make sure they are healthy.
 

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Jo it depends on the place.
I had one test it’s output while it was in the vehicle.
Though I kinda wonder if they did it or not as the car kept going through batteries at the time(different car not my smart)
You can test the output both ways though.
One thing I’ve noticed is the smart delays alternator output till after a few seconds after the engine is running(my load tester also checks alternator output)
Dealers or anyone with a high end enough scan tool can check the alternator with it in the car(I can on gm vehicles with my tech-2 clone)
 
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