How to recharge the AC on 1997 Ford Thunderbird

There is no "blue capped recharge port" on this car. I assume it is a R134 system. There is a black capped port that looks like a recharge port. Can I recharge at that port with an R134 canister?

Asked by for the 1997 Ford Thunderbird
The factory caps are black not blue. Yes you have a R134A car. To service the car properly you need a gage set that reads low and high side gages. NOT A SINGLE HOSE RECHARGE KIT FROM A DISCOUNT PARTS HOUSE. Only if you like playing russian roulette. You have a leak most likely in the evaporator. This repair is well above your level of expertise.
so if A/C was working fine for a few years then started to get warmer..does that automaticaly assume the evaporator is leakin..or just needs a can of freon?