Has anyone ever converted this. Ac compressor to an air compressor. I want to run train horns. But I am not quite sure on how to convert it. And most videos are not very. Detailed

 

My dad did that 40 years ago when AC compressors were the piston type. It wasn't difficult. Just hooked up a hose to the output of the compressor to a air tank.
The input side he put a short hose with a filter. I'm not sure about the wiring, but you will need a pressure switch to shut of the compressor with the tank gets
to a certain pressure.
But here is the problem. Back then he used a piston type compressor that was internally lubricated. I believe todays AC compressors are radial and have oil circulating
with the refrigerant. Without that constant oil circulating, I would not expect the compressor to last long.
IMO, it's probably easier and safer, although more costly, to just get a 12v compressor and holding tank.

 

+1 ^^^

Welcome to the forum

Not sure you could do it and make it last with newer AC compressors, they need OIL in the "Freon" to keep them lubed, not sure how you would inject oil into a compressed air stream and then filter it out

I think you would be better off with a smaller compressed air tank, which you would need in any case, and a small 12v compressor