C70: Sound system advice.

[SeeSeventy]

Hey guys,

I very rarely use my C70, buuuuuut as of late I find myself using it more than my bicycle due to the amount of running around I seem to have taken on.

I remember posting about this before, but I have the premium sound system amplified and it does sound awesome, when it works. 99% of the time it sucks. Hissing, whining through the speakers, right door not working, then the bass not working. Then you hit a bump or make a turn and it booms back in. Then its off again. Hell even when you are stationary it plays up. You can usually cure it by pulling the boot or petrol flap over and over until it 'knocks' it back on to work properly. So, I have lived with it and just driven around with my petrol flap constantly open.

But, I decided I wanted to investigate further and after inspecting ever door and speaker, I can confirm they all work and getting power and nothing cut or corroded or missing. SO, I can only assume the SC901 head unit is no longer working. Which is a shame as I would look to keep it looking stock with the iPod adapter, but I can't listen to hissy and whining music, you can drown it out by turning the volume but it blows your head off if it kicks back in and doubles in volume again and the switching of the petrol and boot no longer works as intended. A bench test came back okay, but it can't be anything else. I thought about another earth off the antenna but the current is like the day it left the factory. But, it gets incredibly hot, almost scary hot.

I guess I would like to hear some feedback from anyone who has used one of these kits here and whether it truly allowed you to just swap the head unit and use the current amps and speaker set up without compromising sound quality or clarity? I give up on all else and am not really in the mood to continue testing the same old stuff or pay an auto electrician.

http://www.ebay.co.uk/itm/3508432792...84.m1423.l2649

[kevvydude]

sounds like a loose or broken wire, just check the plug and the back of head unit , also the speaker connection,if the other two options dont fix it, but it does sound like losse connection m8

[SeeSeventy]

Originally Posted by kevvydude

sounds like a loose or broken wire, just check the plug and the back of head unit , also the speaker connection,if the other two options dont fix it, but it does sound like losse connection m8

Cheers for the response, we've spent £300+ on auto electricians who can't solve it, one fixed it for about a week, but it came back. Everything is in tact and a lot of wiring I have cleaned up and soldered better connections. I assumed it would be nothing more than a dodgy connection but everything is secure and as you would expect. Nothing reads irregular on the tester either...

It's a real strange one, I have even insulated some connections to be on the safe side. I cna't get my head around it. If it's not the head unit, I think I may have to sell the car it's getting that bad...

[mikealder]

Start with the 6 pin DIN plug that goes in to the rear of the head unit and the other end of the cable which goes in to the amp, if this is breaking down then you will have plenty of issues with sound dropping out and hissing from the amp, as you can hear the hissing the speakers and output from the amp must be connected (otherwise it would be silence) so go after the input feeder to the amp which is the DIN plug lead - Mike

[SeeSeventy]

Originally Posted by mikealder

Start with the 6 pin DIN plug that goes in to the rear of the head unit and the other end of the cable which goes in to the amp, if this is breaking down then you will have plenty of issues with sound dropping out and hissing from the amp, as you can hear the hissing the speakers and output from the amp must be connected (otherwise it would be silence) so go after the input feeder to the amp which is the DIN plug lead - Mike

Thanks for the info... I assume to chase this all the way to the amp from the back? The whining seems to pickup electrical noises on the car, speeds up with engine, enhances sound of indicators etc... It's like a cross between a hiss and a whine... I have to try and release the passenger side motors on the seat on the weekend, I will have a look and chase the wire all the way down. See if anything is a miss there.

Thanks, I will keep updated. If no luck, I do have a test head unit to try this adapter. Don't fancy switching the whole system... Don't even have the money for that! lol

[mikealder]

What you describe sounds like Ground Loop Interference, this is often caused by different voltages at the point where the amp earths to the car body relate to the ground point used by the car head unit. You can purchase GLI filters but they use RCA plugs so more adapters to go from din to rca then back to din would be required to try one of these.

I would make sure the amps earth connection is clean, if possible remove the bolt from the earth point and clean up the tags/ structure where it connects to the car before bolting it back up. The earth point for the amp is 31/11 which can be found here:



The main earth point for the head unit is back at the fuse/ relay box under the dash looking up between the pedals it can be seen, far from easy to get at that one - Mike

[Luxobarge]

Gotta agree with Mike there - definately smacks of an earthing problem to me.

[SeeSeventy]

Originally Posted by Luxobarge

Gotta agree with Mike there - definately smacks of an earthing problem to me.

You'd think wouldn't you, I have put in an extra earth from the antenna. I had the whole boot stripped and every point checked. The only thing I haven't done is check the DIN cable from the amp to the head unit. The head unit has perfect connections all round... The one point I haven't checked is the earthing point under the fuse box you mention. I've had a quick look this afternoon and I think I can see where you mean. I have a semi built cockpit at the moment as the headlight switch was causing an issue where it had snapped. Funny enough, since replacing that switch the petrol flap and boot lid trick stopped working.

I will dedicate my morning tomorrow to it, I will again check the 31/11 area and do what you have suggested, see if anything I may have missed. It's certainly possible, I have been over the entire accessible loom.

I ordered a cable and ISO to test a head unit I have here as well, so with some luck I should have a solution tomorrow whether it be factory or aftermarket.

I'll let you know how I get on, either way. Thanks so far

[mikealder]

When you locate 31/11 and take the bolt out if you can see the copper wires through the crimp see if they are still copper coloured or have they turned black, it might be water ingress down the cable that has oxidised the copper turning it black which makes it higher resistance - Mike

[SeeSeventy]

Right, had a few hours doing odd jobs and I dismantled the boot and amplifier. I checked all earth poi tz again and they are as new as the day they left the factory.

However, upon playinv with the 6 pin din it sprang into life again. A few more wiggles and it was in and out. The rubber seems a little dry but nothingout of the ordinary. I am going to check the amp connection and try running a new din for a few days and see how I get on. It would seem a bit of damp may have been in there at some point but nothing to cause any corrosion to wiri g.

I will see if the new cable solves it first, but if the amp is the problem I need to think again what I am going to do. I'll uodate the post when new cable arrives.

Thanks for the directions again... after checking it all before I am shocked that this time it seems to have shown something that could be causinv it. 5th time lucky by my count! Well I hope anyways. Dash/hwad unit earth was fine az well.