mattski

Hi,

Over the weekend a mate and I finally managed to install my new hifi kit in the car. This comprises of the following bits and bobs:-

Kenwood PS9590R headunit
Kenwood 12 disk changer
Alpine MRV357 V12 amp
Infinity Components in the front doors
MB Quart components in the rear doors
13" focal sub + focal box.
Oxygen free cable rewire throughout (all soldered).
8AWG power cable to the battery with 60 amp fuse.
3x OFC Phono interconnects from the headunit to the amp wired front, rear and non-fading.
The amp gets it's power on signal from the headunit.

This sounds yummy (imho) and am very pleased. The guy who I helped do it is a qualified installation geeza...so whats wrong?

Well... The head unit has never been quite right imho (see my previous post) and as Chiark suggested the headunit was driving a 2 ohm load.

Now something rather odd happens. All of a sudden and for no reason a rapid 'clicking' sound will appear from the speakers and I can't figure out what it is. The amp is still working and volume control from the headunit still works (i.e. I can turn up the volume over the clicking sound).

This clicking only goes away if I put turn the head unit off (or standby which shuts the amp down).

So the only things I can think of are:-
1. Something not quite right with the amp, although it works fine throughout the clicking sound.

2. The headunit. I suspect it may be this, it appears to be having real problems with power for some reason (the old kenwood was fine) and now it's not even using it's internal amps. The clicking is present no matter what source is selected. It kinda sounds like the clicking a relay would make and is pretty rapid.

Radio quality is very bad (and seems to fade) and there is the word 'IN' on the headunit which, according to the manual, means 'the cd player is malfunctioning'.

The manual only suggests that this may affect the actual CD (it says eject the CD!).

Help! Any suggestions would be most welcome.

ta,
matt

SecretAgentMan

Does it crackle just when the ignition is on, or is it there as soon as you ower up the headunit?
It's very unusual to have any problems with the engine off.

Is the crackle still there if you unplug the RCA leads from the amp?

If they go away with the RCA's, it's either the headunit, or something that the low level leads are picking up on the way...are they placed by any chance near the fuel pump?

If they're still there with the RCA's out, it's the ground messing with you.

Get out there and get some trial-and-error-ing done mate.

/J

mattski

Hi Dude...
<B>
Does it crackle just when the ignition is on, or is it there as soon as you ower up the headunit?</B>

Good point... The clicking has only been present with the engine running (I *think*) but it's not there all of the time, it's fine for ages and then all of a sudden comes... Once it is there is appears much quicker, something getting hot perhaps?

It's very unusual to have any problems with the engine off.
<B>
Is the crackle still there if you unplug the RCA leads from the amp?</B>

Will check that...
<B>
If they go away with the RCA's, it's either the headunit, or something that the low level leads are picking up on the way...are they placed by any chance near the fuel pump?</B>

Hmmm, don't think so. The fuel tank is behind the back seat in E320s and the phono's run with the original wiring loom to the back of the car. They all run together and are insulated. If it was the fuel pump wouldn't the clicking be there all of the time?

<B>
If they're still there with the RCA's out, it's the ground messing with you.</B>

hmm..ok...

<B>
Get out there and get some trial-and-error-ing done mate. </B>

sigh...here goes thankyou for the suggestions...
Matt

chiark

If it's RPM related, it may be your HT leads which have a small crack in them. My system crackles when an electrically noisy motorbike is near, so this'd be my bet...

Answer may be to try another set of leads. If this is in the Merc that's a few years old, it's easy to replace.

Nick.

mattski

hi guys,

after a bit of a process of elimination I've found it only happens when the engine is on.

I listened to it for a good hour without the engine on and it was fine, turn the engine on and a couple of songs in and we have the click-click noise.

So, what should I do to get rid of it guys?

ta,
Matt.

chiark

Try the HT leads?

I'm on chat at the moment (chat.scoobynet.co.uk)

mattski

Chiark,

If it was HT leads wouldn't the clicking frequency increase with engine speed? The clicking has a constant speed, the only thing I can think of is the fuel pump?

ta,
Matt

chiark

Sorry, didn't read/realise it wasn't RPM dependent.

The fuel pump runs at a constant speed, and I did have that problem in a Clio, so it may be worth a quick check...

Nick

mattski

ok... so what is the best way to check and if it is that whats the best way to fix it?

Interestingly I didn't get any 'clicking' noise today on the way to work and thats a 40 minute drive....odd hey!

chiark

Damn strange, Matt. The way I found it was by re-routing the RCA cables that go near the fuel pump wiring and motor... Dunno where that'd be in the Merc.

To be honest, if it's intermittent then it'll be a swine to find...

Nick.

mattski

Guys...

I *think* I have found the problem

I was doing some testing earlier this evening and realised that I probably had the air conditioning on whilst driving and listening to the stereo.

So I tried switching the ignition on (no engine) and starting the blowers. Sure enough, a couple of minutes later the clicking appeared. Upon turning off the blowers the clicking immediately stopped.

So I repeated the test three times with just ignition and a further three times with the engine running. I am convinced that it is the blowers causing the clicking noise.

So, where next? What about putting ferrite chokes on the phono cables? I suspect that they are picking up the interference as prior to installing the amp the headunit was fine driving the OEM speakers.

what do you guys think?

regards,
Matt.

chiark

I wonder if there's something you can do to the aircon compressor to shut it up electrically. Maybe it's worth checking for loose connections, etc?

Ferrite chokes, in my experience, don't make much difference. Still, I've never had this problem so it may be what you need?

At least there's a solution