1993 Prelude V-tec.

I have a problem with my a/c. It blows cold, then blows hot, then cold again. It does it about every five minutes. I had it checked for leaks and none could be found. I put more freon in it to top it off just for the hell of it.

Compressor is not cutting off, switch is not bad, maybe expansion valve??? I was going to run a dye thru it but I was told not to.

What would seem to be my troubles?