I had the "bulb failure" warning light come on for the first time this week (not bad in 5 years!). On checking all the lights I discovered that the second on the rear running lights (P21W) was not working. I replaced with a new bulb and the warning went out. Out of curiosity I checked the old bulb with a 12V power supply and found it still illuminated. Is this because the bulb filament is aged? My suspicion is that the running light only receives 5W under normal conditions and the 25W is 'high intensity"
I am correct?