Defogging problems - 1974 W115 240D

[j-galap]

Hi folks,

I'm having a couple of defogging issues with my 240D.

1. The rear heated screen works well to begin with (using the pull switch on the centre console) but if you need to use it more than a couple of times it turns off almost immediately. What would be the problem here?

2. The interior fan switch is a little temperamental. Initially, it works well, but after driving for a while with the fan on it will stop. I've realized that if I hold the switch not at 'resting' (as in: just before it flicks on to the next setting) the fan comes back on. I'm sure it's an issue with the switch, not the fan. Any ideas?

Any help with this would be greatly appreciate

Cheers