I have tried hooking up a standard R134a charge coupler to the low side on my XJ-8 and the coupler is to small. Is there an adapter that is needed to charge the system. My machine has fit anything else I needed to use 134a on. I'm puzzled. Any help appreciated Jim

 

I assume you are talking about the quick-disconnect fittings? Most cars have one smaller and one larger coupling. Is yours even too small for the smaller coupling?

 

the charge coupler is to large for the smaller (high) side pipe.