Has anyone tried to disassemble hi\lo pic horns? I bought 2 but the low pitch is not coming on. I tried tapping but nothing seems to work. Has anyone try to open one of these and cleaning out internally?

I did.  There are four tabs that hold the round cover on the horn.  Gently bend them out with a small pry bar (screw diver) and the cover will lift off.  Most likely problem is burned points in the electrical side.  I used 600 paper to "file" the burnt part off the points.  All is well.

I have done the same thing with good results.

I tried to file down the points on the horn but horn did not work. I found out that the problem was at the points they were not even touching. I tried to bend points plate together but I was not able to. I proceeded to drill out points rivets to clean & adjust points. I was able to make the horn work. Replaced rivets with screws.