Ford Puma 1.6 2001
The original Ford 6000 CD player wouldn't tune 99% of the time and as they are known to go wrong I replaced it with a new Panasonic head unit and used an Autoleads ISO wiring adaptor harness.

Problem is this...

Turn key to position 1: Radio works faultless
Turn key to position 2 or when engine running: Radio tunes fine but has interference, almost like a rhythmic crackle every second or so.

What could be causing this? I've seen you can get an inline noises suppressor filter for the power wire. Is this worth doing?

I have tried routing the wires a bit better, away from the aerial lead etc but problem persists.

Please help as it's driving me nuts!!

 

They normally have a built in suppressor so you could try and locate where that is, I.e in the loom, alternator, etc

 

very unusual to get this on modern cars as this used to plague us old farts on cars from the 70s'80s, could be down to a missing earthing strap or maybe the coil pack,ht lead