I'm trying to see if if my recently acquired 90 740 turbo is only in need of an AC recharge. Anyway, I took it to a local place and the mechanic didn't have the right fitting. The low pressure fitting has a black cap and a schader valve. I have an 89 that was converted and the accumulator looks the same but it has a blue cap with what I think is a r134a quick connect connection. It looks like an adapter was screwed onto it to change the "black cap connection" to the Blue quick connect.

Am I correct and can the fitting off my 89 be taken off and put on the 90 for recharging? Is the black connection uncommon in the AC world?

Thanks, as always!
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Paul NW Indiana '89 740 Turbo 140,000