Radio interference when brake pedal pressed - T6 Ocean 204 TSi

Looking for any pointers to a problem with radio interference, please. I'm getting radio interference when the brake pedal is pressed; annoyingly this isn't happening when I visit the dealer so they're unable to investigate. Problem seems to be worse when the vehicle is warmed up and has been in traffic. Pressing the pedal causes static/sizzling sound to interfere with the radio, releasing pedal stops the interference. Dealer Technician hasn't come across this before. Anyone come across this type of problem before? Any self checks that I could do to gain more info to pass on to the dealer Technicians?

 

Hi tell your dealer to look at there technical information TPI’s it’s a know problem I cannot remember the fix off the top of my head but I can look it up on Monday morning.

 

Thank you VW Guru, that's good news and I'll mention that to them on Monday!!

 

Hi I have just looked at the technical information this morning and it states there is a software update being worked on by the factory and no repair is available at the moment. I would say it maybe worth just talking to your dealer as the tpi is titled radio reception briefly disturbed when braking.

 

Thank you for taking the time to check that VW Guru, I'll advise my dealer - it's an annoying and irritating feature that I can well do without!

 

Interference suggests that the system isn't properly protected from EMC interference but should be relatively easy to sort.

Tracking down where this is happening can be very challenging for someone not experienced with EMC/RFI and I doubt a dealer would be able to track it down but they can apply ferrites and as it's brakes interfering with stereo there are only so many items that could be causing it. Probably the LEDs aren't EMC compliant and the cables are transmitting the signal.

With ferrites applied to various parts of the wiring around the stereo and especially around the brake light wiring, it should stop it from transmitting and picking this up.

 

Thank you Matt, it will be interesting to see if the VW software fix cures the problem or whether ferrite screening as you mention is needed. It really is quite a racket when it occurs!

 

If it’s causing radio interference I don’t see what software can do. I expect it will be hardware and the cabling radiating that interference.

After doing amateur radio for nearly a year I’ve learned a lot about this stuff but only really scratched the surface.

@Martin and @motacyclist may have a view? I am only a novice at all this

 

Should have said EMC is electro magnetic compatibility. LEDs are kind of notorious if they aren’t made to standard.

 

Don’t quite understand if the problem occurs when the pedal is pressed and the van is static. If it only occurs when the van is moving then the problem could be caused by the pads rubbing on the discs causing static.

If it still occurs when the van is stopped then it could be caused by radiation from the canbus system delivering the instructions to the braking system. If you’ve ever tried to listen to a weak signal on the radio you’ve probably heard all sorts of C3PO noises coming from your computer or mobile phone, the noise varying with whatever the computer is doing or what I’d displayed on the screen.

If it’s a known problem by VW and they haven’t been able to fix it then there’s probably not much we can do.

Might be worth taking a portable radio in the van to see if the interference has any effect on that; you could try moving it around different parts of the van to try to locate the source of the interference. Try it on different bands, LW MW VHF and DAB if possible.

 

Presumably something to do with the spark plugs and associated electronics if only present on TSI engines.

 

I was just pondering this issue. Spark plugs would be a constant issue, braking would instigate the ABS pump running in preparation so would be an issue for all fuels. RFI generation is not something you can normally combat with a software update.

 

I suspect if it was spark plugs it would also change with engine speed and timing? I had a interference problem on my old T25 probably from the distributor cap as it changed with speed but with a few ferrites the problem was eliminated.

I do have some basic Electrosmog detectors, so if you're nearby I could maybe have a scan through and see if it can spot a source? If its effecting FM radio it may be in the VHF spectrum which I can detect with it. Although as mentioned above a basic AM radio would do similar.

 

My first thought when I read this was probably arching from the brake peddle switch as that has a bit of current to switch with the current from the brake lights (not controled by the bcu).

 

Hi it’s affecting both petrol and diesel it a random fault some T6 models suffer some don’t no real rime or reason as to what spec causes it. I also doubt software will fix it that’s just the normal wording these days on we don’t have a clue how to fix it yet

 

How very true!

 

Certainly an easy fix if it is as long as you can find a good replacement. That would result in a quick buzz upon pressing then go away whilst being held down, unless the contact was very bad which could lead to a continuous arcing.

 

Hi there is no mechanical brake switch on T6 or it’s variants it a Hall effect sensor on the brake master cylinder

 

Many thanks to all that have taken the time to think about this and post a reply. I have asked my local dealer to check out the TPI that VW Guru alerted me to and I have arranged to visit them and hopefully replicate the interference for them to witness first hand. I'll keep you posted on progress. MattBW, thanks for your generous offer of an 'electrosmog scan', I'll keep that option open if I may - pending VW checks at the dealership. Motacyclist - I'll check what happens when applying brakes at a standstill and try the portable radio idea.

 

An update on this. The interference occurs on FM and when the DAB band is chosen and the DAB signal drops out and FM is resumed. Interference is present when at a standstill and brake pedal activated. To get the interference to perform requires vehicle warmed up, it's not evident from cold. I've now demonstrated the interference to my local dealership technicians - their initial thought is to change out the FM antenna in one of the wing mirrors and they are aware that there is a VW TPI on the issue. I'll let you know how this works.