I have just solved a minor but troubling fault with the SII 505.
The LHS indicator had stopped working properly, (parking lamp flashing at 20 to the dozen). Globe OK and wiring to the unit also OK.
After much head scratching and consultation with the learn-ed one , it was considered to be a bad earth.
Then the task of tracing the harness to where the earth goes.
For those not in the know, look for the white plastic block screwed to the front apron metal, behind the receiver/dryer, behind the battery, under the birds nest of wires. It appears that it is prone to getting general crud and grunge cake on to it.
Remove the connectors and clean/spray drown in WD40/CRC/RP7 etc.
The indicator now works as it did the day it left the factory, (if not better).
Now here is the strange thing:
The central locking now works without hesitation, (previously, occasional glitches, where several goes at key turning required to unlock). The headlights are brighter and do not dim slightly when air con/windows/ other accessories used. In other words, a multitude of other things are improved.
So if the ashtray illumination is not working as it should, check the white plastic block screwed to the front apron metal, behind the receiver/dryer, behind the battery, under the birds nest of wires.