Hello guys, I have a Ford focus ecoboost 2015. It is a car S and been bodged together. I’m in the process of getting everything sorted on it as I quite enjoy this car. Anyway one of the damaged parts left on the car is where the high pressure hose for aircon connects the alloy of the pipe has been bent and crushed.  was wondering how easy it would be to replace this part or should I get it done at a garage? Or could I just recharge the aircon manually through the low pressure connector. This is all because my aircon is pretty much non existent and just want to be cool in my car. 

Any proper replacement of part of an A/C system requires first extracting ("recovering") any refrigerant in the system (by law you cannot just let it escape into the atmosphere), then replacing the part, then pulling the system down to a vacuum to extract all air and moisture, holding it in a vacuum for a period as a basic leak test (the longer the better, ideally the system should also be filled with nitrogen for a pressure test but most services won't bother with that), then finally presuming no leaks were detected which would need to be fixed first, refilling with the correct amount of refrigerant plus possibly some replacement oil.

Note that it's a good idea to take the opportunity while the system is apart to replace the valves in the service ports as they are probably the most common place where leaks develop.

Considering DIY; I haven't written in detail about this before so I'll dump a detailed write up of some of what I've learned from my own past research:

• Refrigerant is a hazardous substance. There's a risk of frostbite, blindness, asphyxiation, and whatever else. It may also be flammable.
• You've got to make sure that you use the correct type. Decades ago we used CFC-12 (also known as Freon). This got replaced by R134a in the '90s after it was recognised that CFCs were damaging the ozone. Recently we've been making use of alternatives like R1234yf since R134a is about 1400 times as damaging to global warming as an equivalent amount of CO2. Hence why dumping R134a out of your system to the atmosphere is illegal (and unethical). Note that you can't just put in any type you like, you have to put in what your system was designed for, or at least something known to be suitably compatible with the system in your vehicle, should anything else be.
• You can buy cannisters of refrigerant that you can hook up to a service port to refill with. You don't really want to be just dumping in any odd amount though, you should fill with the correct amount specified for your system if it's to work properly. The quantity is given in weight, so determining how much has gone in is determined based on comparing weight of the container before and after. How practical refilling to the approximate correct amount is to achieve with such canisters I don't know, I've never personally tried. Note that it's illegal now for anyone to sell canisters that are not refillable, and you're supposed to take/send them back for reuse. A professional machine, as used in garages, won't just connect the large tank they contain to your system and open a valve until the weight of the tank drops by the programmed amount, it'll use a compression pump (hermetic kind as found in your fridge) to drive the refrigerant in, and it'll also compensate for the amount in the hoses and recover what's left in the hoses afterwards. Sometimes even with professional machines and their compression pumps you need to turn on the engine and A/C system to help get in the full load. Note also that you shouldn't be putting refrigerant into a system that has a leak or that you aren't suitably confident is leak free. While you may be permitted as a non-expert to purchase refrigerant canisters, I believe that you still have a legal duty, not just an ethical one, to act responsibly towards the environment in how you use it - only doing so if reasonably confident it won't just quickly leak out.
• After replacing a part, to pull the system down to a vacuum prior to refilling you'd need a suitable vacuum pump and vacuum pressure gauge. Not all vacuum pumps are equal, you'd need one capable of pulling 29.92 in. Hg (inches of mercury) to achieve a suitable vacuum. You'd also want a 'manifold' (a set of hoses, valves and gauges) which will allow connecting the vacuum pump to both service ports, and a pair of 'couplers' to make the actual connections to the service ports (different shapes/sizes are available for different refrigerant types). Since the system should just be full of air and moisture you will just dump the output of the vacuum pump to the atmosphere in this case. Once vacuum is achieved you'd close a valve between the gauge and the pump, turn off the pump, and leave it for a while (I suggest at least half an hour). When you come back you'd check the gauge (showing system pressure) and if the vacuum has dropped then you've definitely got a leak and you'd have to find and fix this prior to refilling. As mentioned above, ideally you should also do an (environmentally friendly) positive pressure test with nitrogen, though professional machines and processes used in garages seem to tend to skip this, probably for cost reasons, it's more of a thing you'd typically only find private A/C experts, HVAC professionals and fridge/freezer repair people doing. To do the nitrogen test would require a tank of nitrogen and you'd have to pump some in (compression pump best, vacuum pump connected in reverse may do), and then you'd similarly wait a while and recheck pressure to see if a leak occurred, then you'd vacuum it back out (either just into atmosphere, or into the nitrogen tank though this may contaminate the tank with a small amount of impurity). Doing a nitrogen pressure test would give the opportunity to add and circulate some leak detection dye around the system to help find any leak. When attaching the refrigerant canister to refill you'd need to be careful to not break the vacuum. I think you'd simply just have to unscrew and then remove the couplers, and then attach the refill canister, but I can't be certain (the only decent demonstrations I recall seeing were professional machine based processes where the machine is hooked up and connections left undisturbed for the entire process).
• Emptying the system of any refrigerant (extraction/"recovery") is actually illegal to do unless you've been suitably trained and certified, which costs a lot. You'd have to use a vacuum pump for the extraction, pumping the extracted fluid into a suitable container. You'd of course have to use a safe and suitable container and make sure that in doing so you don't increase pressure in the container to a point where it could explode (you'd need a pressure gauge on the container and would need to know its pressure limits, noting the limits could be lower than advertised if damaged or old and corroded inside). You'd want to filter out any moisture before it gets to the container (and maybe also the pump to protect it) since if you're going to recycle the refrigerant you wouldn't want to put that moisture back into your system (it combines with refrigerant to create an acid that can eat away at and damage your A/C system), and also you wouldn't want the moisture in the container since it may similarly ended up weakening it. (You'd also want to have emptied the container before starting, pulling it down to a vacuum and closing a valve, to ensure it doesn't contain any air/moisture to begin with).
• You may want to recycle (reuse) the refrigerant you've extracted, meaning putting it back into your A/C system (as opposed to taking it to an industrial disposal company). Let me introduce you to the term NCG. NCG means non-condensible gases, referring to gases that are non-condensible (will remain gaseous rather than condensing into a liquid) at pressures applicable to A/C systems or refrigerant containers. This includes air. This is one of, if not the, most complicated part of any professional A/C recovery machine. These machines will have a tank containing refrigerant, they get hooked up to a vehicle, whatever is inside the vehicle's system is vacuumed out and pushed into the tank, which could be pure refrigerant (hopefully of the correct type because mixing types contaminates machines) but could also contain some unknown quantity of NCGs. The machine then has to be able to tell how much refrigerant vs. how much NCG is in the tank in order to indicate to the operator how much refrigerant had been in the vehicle's system, and also in order to only allow refrigerant to be pumped back out (which is also aided by extracting from the bottom of the tank). I believe they have a venting mechanism to automatically vent out any NCG into the atmosphere to get rid of it (it will calculate, vent, and repeat, until the tank contents are about 99% pure refrigerant). The pressure in the container will need to always be such that refrigerant is liquid and NCGs are in fact gaseous. Determining the ratio of refrigerant to NCG in the tank is done by knowing the empty weight of the tank (at full vacuum) and taking certain measurements on the tank - pressure, temperature and weight - and consulting a data table. If you similarly wanted to recycle any refrigerant you'd extracted from your car in order to avoid waste or unnecessary expense, you'd need to do the same thing, plus adding a bunch of extra refrigerant into the tank to ensure when sucking it from the bottom you avoid sucking any non-vented air (and to compensate for the common situation of there being less refrigerant in the system than it should have due to leakage). Being able to do this though requires knowledge of temperature-pressure-weight relationships for different ratios of NCG-refrigerant combinations and I didn't find any useful data on this in my past research. Or at least that's how you'd do it properly; as a cheat you'd perhaps be able to get by by just venting gases from the top of your container until liquid refrigerant starts coming out, presuming the given quantity of refrigerant would still be liquid at whatever pressure remains when all NCG is gone, though this method is imperfect in terms of obligations to protect the environment.
• Your system contains a certain quantity of refrigerant oil (type and quantity should be stated alongside the details of refrigerant quantity). Some will be in the pump, some spread around other parts of the system. Some oil can come out of the system I believe during vacuum extraction. I believe also some of the vacuum pump's own oil could potentially leak out whilst it operates. For the latter you'd maybe be able to arrange your container hose such that it drains right back in. For any oil coming out of your A/C system, I believe the professional machines filter this out into a small translucent plastic container at some point prior to the extracted fluids reaching the tank, probably before the vacuum pump. The operator can then measure it and put back an equal quantity into the system. Oil is added to the system via an 'oil and dye injection' tool. (You could take the opportunity to also inject a little leak detection dye).

Practically speaking when it comes to A/C work, for most it's best to just get a mechanic to do it all, or at least the recovery phase. You could perhaps arrange with them for them to extract the refrigerant, you could then take it away and fit the replacement part yourself, then either you could try to vacuum and refill yourself per the above, or go back to the mechanic for this. You may want/need a record of how much refrigerant and oil were extracted.