I have an 09 JCW hardtop HiFi where I just finished installing replacement speakers, adding a sub and a 6 channel amp in the boot (Focal components in the front, Image Dynamics 6x9 in the rear and a 10 inch pioneer ib flat sub in a false floor in the boot with a JL audio 6 channel amp built into the false floor. I pulled the pins from the factory amp for input and output into the new sub and used the remote turn on line from the factory amp as well. I ran power for the new amp from the battery through the provided nipple in the firewall and along the right side of the car. The new system was working perfectly (sounds awesome), but I was getting alternator whine even when the radio was not on (because of the CAS system through the 30G circuit keeps the amp on). I was installing ground loop isolators at the input to the new amp and must not have correctly taped the wires, so when I tested, I think the speaker wires shorted and the radio will not power at all (new amp will). The fuse (21) is not blown and neither are any under the hood. Several people have mentioned in an off-hand manner in several posts that there is a fuse behind the head unit in the dash. Can anyone confirm this is the case before I tear the dash apart?

 

There is right on the back of the head unit.

Third picture in this there shows it located in the same area as the plug recepticals

https://www.northamericanmotoring.co...991-post5.html

 

You may want to read through the end of this thread - https://www.northamericanmotoring.co...m-upgrade.html. You should not be getting alternator whine. I'd recommend finding the source of the noise and fixing it, rather than adding more components to try to patch it up.

I'd be curious to know if the HU fuse was blown. I suspect not, but it is possible. The HU has short circuit protection, but I don't know how robust it is. I suspect that something in your setup is shorting signal ground to power ground, and the HU is staying in protect mode. Keep in mind that the HU turns on when the doors are unlocked (even though the display is dark). Are you getting the door chime?

 

Thanks for the replies. Schatzy, your links made short work of getting the dash out. The fuse behind the radio was blown. It "blows" my mind that they have a setup that blows the fuse in the dash before the one in the fuse box. I also figured out that it blew when I hooked up the ground wires of the ground loop isolator. The one I put in was meant to be installed behind the head unit rather than at the amp, so it grounded the wrong side. I have decided, as Kevin suggested, to try and get a better ground. I'm going to shield any power wires close to my signal wires, resand my ground point and upgrade the chassis to battery wire. Hopefully that will get rid (or minimize any noise due to a ground loop). Any other suggestions for improving ground? I put my crossovers in the false floor in the boot on the other side of the subwoofer from the amp.

 

So many folks with noise/installation issues, it is becoming a fun challenge to mentally recreate the install and trying to diagnose the mental model....

A couple thoughts after re-reading what you've written. First, use one of the factory common ground points - this is important. Second, remove any ground loop isolators or other filters. Your signal input to that amp should connect the signal + and - directly to the inputs and nothing else. The differential input on that amp will (or should) reject any common mode noise on the input signal, so shielding - which would be extremely difficult anyway - wouldn't make any difference.

There is a possibility that the noise is being coupled (EMI can be conducted, coupled, or radiated) via your crossovers - anything with coils is particularly susceptible. It is always wise to start by finding out exactly where the noise is entering the signal chain. Try hooking a loose speaker up directly to the amp and see if you get the noise. If so, it is being injected at or upstream of the amp. If not...you get the idea.

Also, FWIW, having your crossovers far from the speakers can have a significant adverse effect - I posted on NAM recently about this, if you look through my old posts you should find it.

 

As always, thanks for the great input. I tried to improve the ground point I was using (under rear boot latch) by sanding and it made a small improvement in the noise--it was still significant enough to be bothersome. So, I went and bought a 12 foot 4-gauge ground wire and used the factory ground point suggested in the Integral Audio Sub installation instructions (I wish I had known about their sub before I started this project). As a note, the factory ground point in my 09 JCS hardtop is farther forward on the right sill than in the installation pictures--almost to the front of the door frame. Moving to this ground point removed about 80% of the alternator whine. It is still barely audible in a quite car as I run through the gears. On a different note, your comments about the crossovers in the boot changing the crossover points may be noticable in my system. I expected the tweeters in the Focal components up front to be quite bright, and even with no attenuation selected in the crossovers, they sound good--just not as "bright" as I had expected. This actually works for me as I prefer the smoother sound you get from a silk dome tweeter. After removing the filters and tuning the amp, my audio upgrade sounds absolutely fantastic! Thanks for all of the help!