Radio interference

I changed the stop and tail-light bulbs to LEDS on my 55-plate VW Golf TDI, but now I’m getting interference on the radio. Any idea?

Name supplied

Check the aerial earth by temporarily undoing the alternator connections to see if this makes a difference.

Initially, I didn’t think the LED bulbs would produce RFI (Radio Frequency Interference) because LEDS on their own don’t. However, the driver circuit needed to operate them can do this.

Some LED bulbs emit high levels of RFI interference due to poor design of their driver circuit. The cheaper ones often cut corners to reduce costs. You may not need to replace them, though, simply add a ferrite choke suppression device around the bulb input power supply. This stops the power supply lead from acting as a radiator of RFI. You can buy these chokes from a radio installer or electronics retailer.

Or else purchase some better suppressed bulbs. The same RFI problem can occur when upgrading headlights to high-intensity ones.