23-11-2022, 09:34 PM
Hi Alan
It's almost certainly caused by voltage spikes coming from the ignition system, which modern solid-state flashers take exception to. Modern "inductive" suppressed ignition cable doesn't work very well on its own at the lower frequencies involved as it doesn't have much resistance. I suspect it's really intended for use in conjunction with plugs already having built in suppression resistors. For Austin Sevens I'd recommend keeping the copper cored leads and adding 5000 ohm suppressor caps at the plug ends. This will considerably reduce the spike energy at source.
If this still doesn't work because the noise is being conveyed along the wiring, then "Slack Alice" Simon's suggestion is a good one. Traditional capacitors for this role were something like 0.5 microfarad in value. You can still buy ones of 2.2 microfarads with a spade terminal to bolt to ground and a short flying lead. I'd suggest you leave on the suppressor caps and try adding the capacitor next to the flasher unit.
It's almost certainly caused by voltage spikes coming from the ignition system, which modern solid-state flashers take exception to. Modern "inductive" suppressed ignition cable doesn't work very well on its own at the lower frequencies involved as it doesn't have much resistance. I suspect it's really intended for use in conjunction with plugs already having built in suppression resistors. For Austin Sevens I'd recommend keeping the copper cored leads and adding 5000 ohm suppressor caps at the plug ends. This will considerably reduce the spike energy at source.
If this still doesn't work because the noise is being conveyed along the wiring, then "Slack Alice" Simon's suggestion is a good one. Traditional capacitors for this role were something like 0.5 microfarad in value. You can still buy ones of 2.2 microfarads with a spade terminal to bolt to ground and a short flying lead. I'd suggest you leave on the suppressor caps and try adding the capacitor next to the flasher unit.