I've got a problem with my speedo to in my 172.... it only works when the radio is off, or a CD is playing! How strange is that!
It's had a Sony cd-player fitted at sometime, and if you have the radio on (or CD playing but with TA on) then the speedo doesn't work. Turn the headunit off though (or just play a CD with TA off) and it works fine!!
Anyone got any ideas please?? I read in another post that the black connector has a wire in it which is for the "speed pulse" but have no idea what that means, could it be any connection to this problem?