Got a really weird problem!!

[RichD1]

We've been away for a couple of weeks and when I went into the garage this morning I became aware of thumping noises every so often. It had just rained hard and I knew the gutter does leak a bit above the garage so I assumed it was. I checked outside and could see no dripping so went back into the garage to try and trace it. The noise seemed to be coming from all different places and I started to think that the ceiling was giving way!!

So I got the cars out as quick as possible and when I went to move the Porsche I discovered that the thumping was coming from the rear speakers even when the ignition was switched on.

Have isolated the rear speakers and no more thumping.

Has anyone any idea what the problem might be???

 

 

[Chris T]

Amp that drives those speakers blowing up..? Wet or just old perhaps? Radio on and off-tune? Maybe your in-car record player had reached the end of side 1 and you need to turn the LP? 

[RichD1]

Hi Chris

Radio is off and no other add-ons connected to it, but a record player sounds good. I did think about the power amp. Where is it located? Can't think it would be damp as it's been in the garage whilst we've been away and previously only driven on dry days.

[proporsche]

maybe the mouse got electrocuted...making no more noise;-)

 

[Phill]

Is there an amp, may not be?

[SilverWT]

With older mobile phones, if you placed them near any speaker the speaker would pick up and sound the tone of the phone connecting with the network on a regular basis.

Therfore, if the radio if off I suspect the speakers are picking up some sort of radio wave. Maybe a "smart meter", or house alarm system.

Just a guess.

 

Mark

 

[RichD1]

It was still doing it when I put the car out on the driveway, but an interesting theory. It was not doing it continually, maybe a thump every 2 or 3 minutes and then maybe a blast of several thumps every now and again. 

[Chris T]

I 'think' the power amp was under a front seat. My car was supplied without so I couldn't say for sure. Many many cars have of course been fitted with an aftermarket amp, they often thump when switched on/off. Does yours have a loose power connection? 

Amp could also be on despite radio being off, any loose connections or interference in output of radio to input of amp could cause it.

[Phill]

1 hour ago, SilverWT said:

With older mobile phones, if you placed them near any speaker the speaker would pick up and sound the tone of the phone connecting with the network on a regular basis.

Therfore, if the radio if off I suspect the speakers are picking up some sort of radio wave. Maybe a "smart meter", or house alarm system.

Just a guess.

 

Mark

 

Do you think if you wrap them in tin foil it will solve the problem 

[Strictly]

Power amp should be under passenger foot board (left side)

[RichD1]

Don’t think I have a power amp when I had the foot board out several years ago. I’ll take another look though.

[Chris_911]

On 23/10/2024 at 21:58, Strictly said:

Power amp should be under passenger foot board (left side)

No - if you have the 'hi-fi' option which includes the amp it is under the driver's seat on a RHD car.

[RichD1]

Just looked at my option list and it had no hi-fi option fitted. It had a new radio fitted before it took ownership back in 2014 so I would think that is not causing the problem.

It’s getting spikes of voltage from somewhere and it is effecting both rear channels. Don’t have front speakers fitted at the moment as they need replacing so don’t know if its effecting them too.

Edited October 25, 2024 by RichD1

[Chris T]

Did the car also have an amp fitted in 2014? Have a look under the dash and see if the radio has speaker wires coming out directly or RCA (phono) plugs leading to an amp stashed somewhere. 

[RichD1]

As I said my authentication certificate from Porsche has no amp option fitted, but I will check when I get her out next. 

[Mobydick]

That’s an intriguing problem.  I guess if you disconnect one of the speakers from the head unit and the noise is still there from BOTH speakers , the speakers must be picking up some external interference. If not, then it’s receiving the power from the head unit somehow.

Also, I think these cars were often fitted with an amp - but modern head units are powerful enough to operate without separate amps.

When I upgraded the head unit from the original blaunpunkt, I bypassed the amp - it’s still under the drivers seat.

[RichD1]

When I disconnected the first speaker it stopped but the other channel was still sounding until I disconnected that one too.

[Chris_911]

Track the wiring from the headunit to the speakers.

[Mobydick]

Whilst its sounding , disconnect a positive speaker wires from the head unit and put a test lamp on the head unit output - if its live, the current is coming from the head unit. What type of head unit have you got?

[RichD1]

It’s a Sony which was fitted before I took ownership of the car so must be around 2010ish. It is the type you can remove the front display panel for security.

I’ve never ever used it as the front door speaker cones had disintegrated so I removed them

[Mobydick]

If you don’t use it, try disconnecting the live feed to the head unit.  Would that silence the speakers ?

[RichD1]

In the end I removed the speakers but it looks like there is an electrical fault going to the head unit as I've just found the battery flat. Agghhh, I've just put a new Yuasa battery on too!!

Hoping it will recharge.

Also noticed that the clock is not working but I'm sure this is not related.

The car is SORN so no rush to fix but I will remove the radio.