Lately I've been doing some bad weather ILS training but for some reason I don't always get ILS indications on my ADI even though I set it up correctly. I always choose airfields that have ILS systems available, and then set the correct ILS frequency, power it up, and select ILS on the NMSP. I take off, come around and line up with the correct runway, but I'll get no ADI indications. Do some airfields have broken ILS systems sometimes? I ask this because at one of the airfields, its ILS system was working perfectly fine in clear weather, but when I changed the conditions to dense fog, the ILS system no longer worked. I thought that the whole point behind using ILS was for safe landings in IMC.