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Am I Killing My Alternator?


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hey, I am running 2 Rockford Fosgate P2D2-12 Subs off 2 Rockford Fosgate P300-2 Amps with a Rockford Fosgate 2 Farad Power Capacitor. My Battery light on the dash flashed a few times over a few days, I checked the battery which was reading over 12V and I checked the alternator with the engine running and it was pushing over 14V so it all seemed ok. Then later that day the battery light on the dash came on and stayed on then the alternator started smoking. I have now changed the alternator for a second hand one and took the car for a spin and blasted the stereo and all seemed well until the battery light flashed again. so im going to keep the volume low and turn the gains down until I can find the problem. I have had the system in the for a few months and never had any problems running one amp, then we run 2 amps with infinity speakers and no problems other than blowing the speakers which were over 10 years old so big deal. then recently we upgraded to the system we have now which is listed above, the only thing I changed was the earth lead, I found a good piece of metal in the boot which I scraped off the paint and clamped an earth lead to it with a nut and bolt, the earth lead is a metre long but I do not know if this is causing the problem, also all wires are 0 gauge.

The car is a BMW E46 330D M Sport, the alternator is 150Amps.

The Battery is fine the car was off the road for almost a week waiting for the new part to arrive, once we installed the new alternator the car started fine with no signs of a flat battery. the battery is sound.

please tell me any information you have that may be of help.

also we know that running the 2 P300-2 is probably not the best way to run these but we are currently looking for a single amp for the subs.

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I'd start with that. It's upgrading your charge wires since the stock wires are only meant to handle the stock electrical load.

1. Alternator positive to battery positive

2. Alternator/engine ground to chassis ground (I suggest the strut tower for this)

3. Battery ground to chassis ground (I suggest the strut tower for this one too)

Also: You said you checked your voltage with the engine running. Did you by any chance check it with the engine running and your system playing?

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nope and I checked it with the system playing but not loud and checked it through the cigarette lighter and also changing the wires from the alternator to the battery is a major job as the battery is in the boot of the 330D

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Ohh really? IIRC those have 0 gauge going to the battery don't they? If so you can skip that and just do the alt/battery grounds

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