Allan's C5, thank you for your helpful post on this topic. I removed the high level brake light from my son's 51 reg estate easily following your instructions yesterday and confirmed that 12 volts was reaching the connector.   However, I just cannot see how to dis-assemble the light unit, to check/replace the resistors as you suggest, as it appears to be a sealed unit.   Any guidance on this would be much appreciated.   Also, as I have returned home and so do not have the car to hand, do you know if the light unit is damaged if the polarity is reversed, as I didn't have my voltmeter with me to check which leads were +ve and -ve yesterday.   Thanks in advance for any help.