Look behind the instruments on that side of bulkhead. There are two connectors sprouting out of chassis loom, a twenty pin (only 19 used) to instruments and the twelve pin to switches. It's this latter one I was referring to. If you are able to confirm the diode appropriate to the side not working when hazards selected is open circuit (as suggested above), then it can be replaced. A widely available 3 amp IN5404 should suffice.
