Whine & a 150A alternator

Hi folks, I've been following a lot of the excellent advice from this forum in my quest to retro fit Bose into a 2004 Audi A2, with a Blaupunkt DAB 54 headunit. I got the amp and sub in OK and these work fine with the genuine Chorus head, but there's always a clicking perfectly in time with the engine firing, as well as alternator whine when I put the Blaupunkt in. The amp and head are both grounded at the battery and the positive feeds are also direct from the battery, by-passing the original harness. I tried to put a cap on the alternator (Autoleads PC5-40), but it blew after a day, because the alternator is rated at 150A output!! Anyone got ideas on how to proceed, or where I can get a bigger capacity cap from? Would it help to put a stiffener cap in between the battery and the amp/head? Cheers in advance. Mike

It sounds like you're overdriving the inputs of the factory Bose amp.  Try bypassing and let us know how it turns out.My ex once told me I have a perfect face for radio.

I've heard that from other topics, but surely, if the HU was overloading the Bose amp, this would happen whether the engine was running or not? The clicking and whine are a function of the engine, not necessarily an overload.

your cap did not blow because your alternator puts out too much current.  The only thing that can really incapacitate a cap is incorrect installation or a voltage spike above its rated range; usually 20-24V.  Since the rest of your electronics are still working fine; I'm going to assume the latter is not the case.  Did you charge it before hooking it to power?Life moves pretty fast; if you don't stop and look around once in a while; you could miss it.

skipton01 wrote: I've been following a lot of the excellent advice from this forum in my quest to retro fit Bose into a 2004 Audi A2, with a Blaupunkt DAB 54 headunit.

First of all, do I understand you are trying to install a Blose in place of a far superior Blaupunkt unit? Why'd you want to go and do something like that?

skipton01 wrote: I got the amp and sub in OK and these work fine with the genuine Chorus head, but there's always a clicking perfectly in time with the engine firing, as well as alternator whine when I put the Blaupunkt in.

A possible fix for that would be either resistor spark plugs or resistor leads. If the clicking you refer to sounds like what I think you are referring to, it is ignition noise, not alternator noise...

skipton01 wrote: The amp and head are both grounded at the battery and the positive feeds are also direct from the battery, by-passing the original harness.

That's a bad idea. SOLIDLY ground the battery to the chassis, and then ground all of you components to the chassis as well. When you ground the components individually to the battery, you can induce ground loops, especially if one of the devices is not also grounded at the device end. Better to use the chassis as the return...

skipton01 wrote: I tried to put a cap on the alternator (Autoleads PC5-40), but it blew after a day, because the alternator is rated at 150A output!!

Obviously you either a: installed the cap incorrectly, or b: your alternator is making a TON of noise, which could blow an incorrectly rated capacitor. Caps are rated by voltage, and as long as it was rated at least 16 volts, and you installed it in parallel, there is no way it could have blown, except for the potential of outside the normal limit noise, as stated above, or heat.

skipton01 wrote: Anyone got ideas on how to proceed, or where I can get a bigger capacity cap from? Would it help to put a stiffener cap in between the battery and the amp/head?

No, caps are rarely, if ever, going to fix ignition noise. If it really is ignition noise, you need to repair your ignition system. Alternator noise, while POSSIBLY fixed by a cap, is more often than not caused by a bad battery, which should be replaced, a bad ground, which was addressed above, or a bad alternator.It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

haemphyst, I'm only replacing the weedy 2 channel (rear) amp as supplied as standard - the HU is a Blaupunkt DAB 54, which is a replacement for the crappy cassette that came with the car. The car is a diesel, so there are no sparks or HT leads and there is alternator whine AND ignition clicking present. The amp and HU are earthed to a distribution block which is earthed to the battery. The A2 is made of aluminium and so getting a good chassis earth is not easy! I installed the supression cap as per the instructions, but there was no mention of charging it prior to fitting, so this could be a cause of failure. The vehicle is brand new and works fine with the factory HU (with or without the Bose amp) and fine with the DAB 54 (only without the Bose amp - ie the DAB 54 is using its internal amps). The supression cap had two red leads and a blue lead. I was told by the manufacturer that the blue went to earth and one red lead came from thealternator and the other went to the feed to the battery, and that it didn't matter which red lead went where.