I have 2 hoses coming out of the firewall for the AC. One of the lines (black went down to the Reservoir) the gray that you see on the left of the picture looks like it was chewed just goes nowhere. It looks like it was headed up and over the engine but I can't find another end to connect to. This could be part of why I'm having problems with my AC not working while I'm idling. If I give it a little gas or moving then it is cooling.

 

The line going to reservoir is the vacuum Source(reservoir is hooked to intake vacuum)
Other line coming out of the firewall should go to the Heater hose Diverter/bypass, in your picture it is the item just under the line in question, where the 4 heater hoses connect, it has a vacuum activated valve.


No it has nothing to do with A/C, refrigerant is probably low.
A/C system has 2 pressure switches.
At idle the pressure in the system is probably dropping below the minimum pressure so compressor is cycling off and on so cooling drops, when RPM increases pressure does too, so compressor stays on.

 

How can I test those 2 switches? The Haynes book doesn't show too much on AC or vacuum.

 

Couldn't find a '97 Ranger A/C wiring diagram, but the switch should be Closed, so 0 OHMs between contacts.

Wiring is like this:
A/C control in Cab(12volts/on)---------cycle switch----------pressure switch--------compressor clutch---Ground

So if both switches pass the 12volts then compressor clutch actives.
If either switch Opens then compressor clutch releases

Both your switches are working or you would have no A/C at all, I am just guess that refrigerant is low from the age of the vehicle.

 

Should I drain it first? When I was attempting to fill it at first it was blue ~15 and red ~70 but after I got half the can in there it was completely red and would drop down into green ~ 40 occasionally. It really never went any higher than around 70 but would always drop down when it would try to kick in.

I see that the system only takes around 7 oz according to the sticker in the engine area.

 

No, no need to drain it.

Also check condenser, in front of the radiator, if it has a fan then it should be on when A/C is on and you are stopped, if there is no fan or even if the is, lol, make sure condenser fins are not clogged with road debris.
The cooler the refrigerant gets when passing thru condenser the cooler it can get in the cab.
When you are driving you get air flow so it cools down, when stopped you don't, so..............