AC repair questions

[BentGear]

The AC has not worked since I bought it 4 years ago. Finally getting around to looking into it. The system only blows in defrost which I understand is probably a vacuum leak.  So I'm starting there. 

 

I see this blue vacuum hose is not connected to anything is that normal?  

 

Also what is this canister that has hoses attached to it? Also it does not have anything attached to the outlet labeled purge, is that normal? 

 

It's hard to find any info on these systems, I can usually figure things out if I know at least what should be connected where. Anyone know of good resources for 1988 4.0 A/C systems?

[eaglescout526]

The blue one is for 4wd. 

Thats the charcoal canister for the gas vapors. 
 

Check behind the passenger side front bumper for the vacuum ball or football and see if it has lines still attached to it to where you can trace and find the broken line to go to the HVAC box for all the doors. 

[BentGear]

Could this be what you are talking about? It was bolted to the engine bay wall. It did have a big Crack where the two plastic pieces came together. I used some JB weld plastic bonder to seal it up. When it dries I'll see if that works

[eaglescout526]

Could be but that’s definitely not original. 

[BentGear]

That definitely was the issue with the air staying on defrost. Now to get it to blow cold. Any good troubleshooting guides. I have seen videos where people recharge with dust off. But is there something else I should try before I open up the system?

[eaglescout526]

There should be a relay that controls the compressor. If that has failed the compressor won’t kick on. There’s also a pressure switch that if it has failed, it won’t engage but replacing that, you have to evacuate and recharge the system.