72 scamp factory air -Do i have to convert?

I would just convert it if I were you, as it isn't bad to do at all and the old R12 is a bit hard to find and EXPENSIVE.
It sounds like you may just have a leak somewhere, as the compressor will not cause low pressure.
It might leak at the seals causing the refrigerant to leak out though.
Really the best advice I could give you is to take it in and have it tested for leaks.
They use a dye in the system and an ultraviolet light to find the leak/leaks.
Once that leak is fixed it's an easy swap to 134A refrigerant.

Personally, I would jumper the compressor to make sure it comes on in the first place, and then go from there with leak checking.