Indicator Probs

[Griff4.0]

I'm having problems with my indicators in that they don't work! I've tried following the wiring diagrams in the Bible but am still struggling.

The hazard lights work fine which leads me to suspect that the indicator unit in the fuse box is OK. All bulbs are OK and all fuses have been tested and are OK. The problem is that I'm getting no feed current at the steering column indicator switch. If I bypass the indicator unit and introduce a 12V supply to the indicator switch exits I can get the indicators on either side to light up so that side of the wiring is OK.

From an earlier thread I believe that there's a diode in the indicator circuit somewhere, presumably to isolate the hazard circuit from the indicator circuit? If that has blown it would create the symptoms I'm experiencing. Anyway does anybody know where this diode is situated? It should be a cheap fix if only I could find the bugger!!

Failing that, has anybody else got any iseas what else could be causing the problem? Or does anybody have a clear wiring diagram for the indicator circuit?