So I pretty much have got everything fixed on my truck now except the air conditioning. The air conditioning pump pully doesn't not
engage. What could be the cause of this. I checked the fuses and they are fine. What should I check next?
Thanks

 

its not as simple as the clutch getting power, there are Low and High pressure switches in the system that prevent the system from engaging the clutch if the system is low on refrigerant to avoid damaging the system which may indicate a leak. Also if your not versed in A/C system fundamentals I'd suggest taking it to a liscenced professional who has the experience and tooling.

 

Yeah, I think I will do that since I am clueless about A/C

 

That system has several o-rings. They are likely leaking and have leaked out all the refrigerant, which by the way is R-12 and the leftover supplies of it ain't cheap. You can look at the joints in the lines and usually see an oily place where they leaked.

 

Does this fitting mean that my system was converted from R-12 to R-134A ? If so can I just refill it with R-134A and see if it works?

 

That looks to be a conversion tip. You can buy the pump at HF to vacuum the system then just add the appropriate amount of Freon per the under hood label. If you aren't replacing big components on the ac it can be pretty straight forward to charge.