I tackled this problem in my landy. You have a problem with the hazard switch. This problems is pretty infamous with defenders. The hazard switch routes the power to the indicators as well. First check if any bulbs are burned out. If all is working, then that just means you have a faulty hazard switch. You can just buy one on eBay. Good luck!
Also check out this website, it helped me (one)tons. :D haha get it, one tons (110).....sorry