mx5cartalk.com

Afternoon all

I installed a new head unit and front speakers in my car about a fortnight ago and all was well. But over the weekend just past, its started playing up. When the car is running, everything is fine, sounds great. When its on accessory I, sometimes, end up with this horrible distortion which overpowers any other sound.

The really weird thing is that it only happens some of the time. I first noticed it when leaving uni last Saturday, put the key in and turn to acc to listen to music while I took the roof off. Sounded busted so I went searching for wires that may have come loose but after 10 minutes or so, gave up and started the car, all came good. Turn back to acc, busted again. Went from uni to a friends place to see what he thought of it, get there and it sounds ok on acc. Turned it on and off again a few times but it stayed good. Drive home about an hour later, a drive that was much longer than from uni - friends place before, and its distorting again. Since then I've made the effort to check every time I've been somewhere in the past few days, both before and after driving, if it works from acc and I can't seem to find any pattern. Sometimes it works after short drives, sometimes it doesn't. Works first thing in the morning on day, then doesn't.

I'm thinking its got to be some sort of power issue but I can't for the life of me think what it could be. With the car off, battery sits at a nice consistent 12.2v. When running at idle with no stereo, the battery is seeing 14.3-14.5v. With the car running at idle with the stereo on, battery sees 14.2-14.4v

For informational sake, the car in question is an NA6. Stereo consists of a 4x150wrms amp powering an 8" sub and 6.5" front splits. Head unit is an alpine dvd unit with the giant external brain box. Any help would be greatly appreciated.

Cheers,
Joe

most problems with noise in car audio can be traced back to the earths.
Also check how close your power / RCA / speaker cables are from others which could cause interference.
is the noise just coming from speakers or sub as well?

definately sounds like bad/rusted grounds!
check your engine bay grounds and all the stereo component grounds are secured onto bare metal.

Thanks guys. I did have a quick look at the grounds the other day, but I’ll have a more in depth look over the weekend. RCA's are well away from everything.

The main thing I didn't get is that it only happens when the car isn't running. Any possible explanations as to why that could be?

I would add a ground to the battery and one to the alternator/engine to the chassis for the motor. make sure it's atleast 4 ga wire Jack.

Are all the 12v sources getting full battery power when switched to accessories?

I had something similar when I installed my stereo (for the second time) in mine. For some reason there was a grounding issue with my RCAs running to the amp. It was odd because I actually bought a better pair of RCAs, but that's not really the point.

I fixed it by looping a bit of wire from the ring of a female RCA on the amp to the amp shell itself (I looped the wire around a screw), thus grounding it. This cleared it up without problems, and it's been running without incident since.

Just realised I never got back to this after I "fixed" it. No idea what I did but it's still fine now, almost a week on.

Pulled the head unit out and reconnected power, ground and accessory. No love, still fine with the car running, still busted when on acc.
Connected new rca's around the outside of the car. Still the same.
Removed, cleaned and reconnected ground and power to the amp. Still busted.
Removed my amp and tried another one a friend had lying about. All good
Dang! Now thinking my amp was busted I threw it back in as a final test and I must have done something right, as it then worked fine.

Again, not sure exactly what I did but I'm not really complaining.