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Greeting from down under. I have a 2001 Mitsubishi Magna, also known as a Diamante in the USA, which has developed some alternator whine through my audio system. I scoped it with a Mini Scope, and need some help interpreting the waveform please. Could this be a bad diode?
This is a Bosch style 110 amp alternator.
Is this noise from something else and do I need to add some type of filter to get a more accurate waveform. This looks nothing like any of the waveforms I have looked at online. Thanks in advance
How reproducible is this audio whine? If it were constant, I would simply unplug the alternator (connector to the computer) and see if it goes away. Unplug it before starting the engine to be safe as the belt will be rather close.
I have trouble reading just how high the voltage is on the pictures.
In Paul's book he writes that the maximum allowable average AC voltage is .3 volt (300mV).
Thanks for the reply. This alternator is not ecu controlled, just a two wire job. The whine is more evident when the alternator has a load on it, either the cooling fans or headlights. The whine changes pitch with rpm and load. DC voltage is fine, 14.4 when cold and 13.6 when hot. I need to buy a clamp and see what the current output is like.
The scope was set to have .1v per division and shows to have 40mv of AC.
I'm having a hard time understanding what's going on with that waveform.
I should have asked but are all the accessories turned on and was the engine was running at 2000 rpms when you took those captures? Are you getting a whining sound from the alternator AND through the sound system on your car? Can you see the ripple on the power feed going to the sound system? What about if you hook the scope up at the battery?
Last edit: 8 years 1 week ago by MaroRussinovich. Reason: spelling
The alternator needs a suppressor --- 2.2uF polyester 250v capacitor with a couple of tail wires soldered on between the +B at the alternator and case of the alternator, this will clean the spikes output.
Also check the ground on the head unit, aerial and alternator.
" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)
Andy - Are you saying that the alternator AC waveform is ok?
That signal doesn't look smooth like other AC alternator wave forms I've captured. Do you think there could be a bad diode? Or, is this AC wave form normal for this car? I have never pulled a wave form for this car.
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