Just purchased a 1988 300CE which has an intermitent indicator problem. Most situations, indicators work fine, but if left on for too long, indicators stop flashing. Bulbs are all good, and both indicators each side come and (and stay on, but don't flash) when selected, when the fault occurs. Once car sits for a while, not running, everything works fine again, so seems to me like this is a heat related problem?. Any advice would be much appreciated.