Whistling interference, frequency and volume dependent on RPM

[PaddyLondon]

MY2000 XKR

I've installed a Nokia CK300 bluetooth handsfree using a Nexxia/Autoleads harness, the Jaguar's factory wiring and StevePAA's connector for RT2 and 5 in the trunk.

With the engine off, everything works fine, muting, call set up, call quality etc.

With the engine on, when I make a call, I send to the other end a loud, high, variable pitched whistling interference along with my voice. The incoming audio to the front speakers is fine.

If I plug the Nokia mike direct into the blue tooth receiver, with the mike wiring 'loose' in the cabin, away from the body of the car, the interference cannot be heard.

I've also tried an OEM jag microphone into the overhead console - whistling interference on outgoing audio is unchanged.

The whistling is RPM dependent - higher the RPM the higher the frequency and volume. I think at above 3000rpm, the frequency to too high to be audible, though it suppresses my "testing 1-2-3 messages".

I've done obvious things like clean and reconnect connectors. One of the connectors in the boot was recently replaced with the replacement's leads etc soldered and insulated.

I'm going to get a Parrot with its microphone installed - but I'm concerned it could be impacted by the same issue.

Advice most welcome. I've just had a service (sparkplugs, something dislodged during work?) and my differential replaced (ouch)

[RichardSEL]

>>If I plug the Nokia mike direct into the blue tooth receiver, with the mike wiring 'loose' in the cabin, away from >>the body of the car, the interference cannot be heard.

No experience with the setup you're trying to install.

Please confirm whether the whistle returns if you don't have the Nokia mike lead loose in the cabin
i.e. does the "whistle" return when the mike lead is close moved around close to metalwork / roof anywheres?

As it's a rev dependent whistle then no supression should be tried at or around the ECU or coils' leads as that might affect their operation. So it's trying to establish what the difference is between the Nokia mike's wiring position and the "neat" wiring you want to use. It may be that there's a bad earth on the "neat" wiring's mike connectors. Screening again (by tinfoil wrap) that loom often helps -- but not if the tinfoil's touching bodywork which could just transfer the pickup from chassis back into the cables again.

Some mikes are connected by a live and a return for the mike which is all within a coax plus the screen so there's three connections. Others only have two with the return being the screen which acts as a pick up for any noise that's circulating in the nearby metal work and so transferred with your voice into the mike's audio amplifier stage

Best I can do from here... Let us know how you get on?

[BrianG]

I agree with Richard's observations about screened leads on microphones, and pickup from body metalwork. However, if the noise is a definite whistling rather than crackling buzz, then it's not coming from the coils but from the alternator. A suppressor capacitor across the main terminals may be all that is needed.

[PaddyLondon]

Brian, Richard,

Many thanks. I'll do some more testing and revert.

Regards

DC

[PaddyLondon]

I did more testing, tried putting foil on the microphone wiring near a connector etc.

No interference on tape, AM or FM radio or inbound voice from a phone call to the front speakers

I realized that with ignition on, engine off, I get noise static that obliterates voice on the microphone.

With the engine on that noise becomes a whistle - but that could be the impact of wiring etc "tuning"/filtering converting lots of sparkplug clicks into a whistle.

So my best guess is to get the spark plugs and coil fitting (recently done) checked.

[BrianG]

If the engine is off I don't think the coils should be doing anything, otherwise the engine might fire randomly on residual fuel vapour, a bit like running on when hot, therefore that would rule out the static coming from there. It's more likely to be some other system interference that comes on with the ignition, although finding which system could be problematic. Note regarding spark plugs: fitting other than the correct Jaguar ones to save money may well cause interference problems of their own. I think from memory that the correct ones have built-in resistors to limit interference.