I posted this on the Audio & electronics forum but did not get any reply...

Just got my HU installed & it sounds much better but I do have a problem though: Occassionally I hear a "crackling" noise...it sounds like a high pitched morse code and disappears in a few seconds.

Sometimes it's a few "dits" & a long "dah". It scares the s%#t out of me if I have the sound cranked up.

Installer said he tapped one of the fuses under the hood for power.

Could it be a loose fuse? According to some it could be a loose or kinked fiber optic cable but he did not use any existing FO cable.

Any thoughts anyone?

 

I would at least inspect his work around the fiber optic lines to make sure something isn't crimped or bending in too sharp an angle.

 

Depending on the sound, it could also be cell phone interference with your speakers. Do you put your cell phone in the cubby underneath the radio?

 

You don't say if it is an aftermarket HU or not, but for purposes of discussion, let's assume you have installed any of the many similar units that are a radio with inputs for CD player or other audio device with copper wire inputs.

It is quite possible that your fiber optic network is dark if you changed to an aftermarket head unit.

I am not sure why your installer "tapped one of the fuses under the hood" for power. Was that fuse under utilized so there was "extra" current available for running another device? I think not. Did he have a clue what circuit the fuse was protecting or was he just a Bozo loose with a stripper under the hood? What was wrong with the power supplied to the radio when the car left the factory?

Does the new HU retain the functionality of the steering wheel controls and the information in the IC (instrument cluster) MFD? (Multi Function Display) You might have done better to add a sub with servo control, and four channel amp for existing speakers for about four Benjamin's if you have the need to hear the sound track from High School Musical at a dangerous SPL. (Sound Pressure Level)

There are a lot of microprocessors operating in a C class car. The engine control unit has one. There are two communications busses, CAN A and CAN B with digital signals on them. There is a microprocessor for the transmission, one inside each door, under the seat of memory seat equipped cars, in the ignition switch, in the headlight switch, in the Air Con system, in the trunk, and other places if you have optional equipment like a sat receiver, a towing module, a telephone, or tele aid. All of these microprocessors communicate using a serial bus and can make the sounds of dit and dah's. The signal can be coupled into your head unit via several different routes. If the power to the head unit is not connected following good engineering practices, the amp may be susceptable to common mode noise. This is when undesired signals enter a circuit on the power cables because they are not connected to a low impedence source of current. A few minutes with an oscilloscope can determine if this a problem. Solutions are proper wiring technique or in severe cases filtering the DC to reject any AC component.

Another possible area to allow undesired signal to enter the amp is on line level inputs. Here again proper wiring of the DC input is important, but also the use of properly shielded leads for the signals carried into the unit. Wire is wire, but the shield coverage in a vehicle should be 100%. Many cables sold in blister packs have a scant 25% coverage.

The radiation from incar sources of the noise you report is fairly small compared to that generated by your yak slab. (Cellular Telephone) These devices feel the need to check-in with the "mother ship" every so often with a string of beeps and boops to alert the network where they are so they can instantly produce revenue for Ma Bell and her ugly sisters.

As a quick test, try turning off the yak slab and driving around. If that solves the problem, you have a choice of a "no Cell phones" sticker on your car, or take the car back to the installer and tell them it is not acceptable. Fix it or money back.

Good luck.

 

I put my cell between the arm rest & shifter...I'll try to put it somewhere else and see if it works. Thanks.

 

HeadUnit: DEH-P5000UB PIONEER

I bought a STEERING WHEEL CONTROL INTERFACE (pac swi-ps ) but I was told it might not work.

I think this was my installer's first Benz install. Here's the story: I initially went to the shop that I have been loyal to for almost 10 years to get an installation price quote for my cupkit. The mechanic & owner who personally works on my car is not there because he is in jail for 'allegedly' sexual misconduct with a minor.
This guy "the installer" was there. I told him I would get my HU/Sub put in first before the cupkit. He said he can do it for me for $80 HU + 80 sub.
After CircuitCity quoted $600. I jumped to the chance.
I assumed he knew what he was doing because the shop works on BMWs & Benzs.
Cut the story short, I was charged $150 for the HU alone 'coz he said it took him a while to take the oem HU out. He even took the vent out without taking the screws out. Now its loose.

It took him a week to finish the job. He works on other cars first before mine. When I checked on it once he was waiting for a phone call for some advise as to where to tap for power.

Did not even install my sub/amp. He said come back & i'll dedicate all my time on your car....I THINK NOT!!!

I will take it somewhere else and let them check/trace his work.


Here are pix of the power tap.

 

You are right jedcred! I had my phone beside my home computer speaker & it did the same thing to it. Glad it's solved.
Is there some kind of gadget you can install to prevent this? This never happened when my radio was still stock. What gives?

This cell interference can't be good for my nuts considering I always have it in my pocket.

 

Keep your cell away from your body as much as possible. That RF will fry all sorts of things over time.

 

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