This guy is clueless. Sure he knows how to work on a car, but a lot of the stuff that comes out of him mouth in videos that's related to more advanced stuff is blatant ignorance. Just watch his totally unbiased views on push-start systems or more advanced cars and the fallacies that come along with what he says.

As far as the air conditioning, the R134a system is a closed system. Because it is a high pressure system there is no way for foreign things to enter, however the molecules will slowly escape over a very long time due to the inherent design of the high pressure combined with rubber o-rings. So it will need to be recharged eventually, but we're talking about five years or longer.
When you want to redo the system you should completely evacuate and recharge the system, don't use any of that crap that Autozone and the like sell to add R134a to the system, it's a cheap bandaid that can cause more issues. If you have the technical know-how, you can buy a gauge setup and cans of R134a in order to evac and recharge yourself ounce-wise. Otherwise, this is one of those times I'd just suck it up and take it to a shop.

As far as the scent, make sure that you AC drain vent is clear. I've never had issues with a moldy smell despite the humid environment here, but I periodically change my cabin air filter and have used these: http://www.walmart.com/ip/36448452?w...056288&veh=sem

 

Thanks. you mean to evacuate and refill with fresh Refrigerant instead of just doing a top up?

How about the compressor lubricant? does it need to be replaced just like engine oil after a while? Thanks.

 

Correct. Evacuate the system and add the R134a ounce-wise.

As far as the oil, it depends on how much comes out when you evacuate the system. Typically you'll need a few ounces, but you don't need to routinely replace it. Shops have nice equipment that makes the job much easier than a DIY. I paid around $80 for a full evac and recharge; considering the considerable amount of time between recharges, even though I'm a DIY guy, I'd rather take it to someone.

 

A/Cs are closed loop systems, meaning there is no escape of the refrigerant. The refrigerant does not wear out. You should never need to 'evacuate' and 'refill' your car's A/C refrigerant, nor should you ever need to add any refrigerant. Never...unless there is a leak!

When was the last time you heard of anyone needing to replace or add refrigerant to a refrigerator or freezer? Vehicles typically go for decades without the loss of refrigerant.

 

That is incorrect, refrigerant can escape. As I said, it takes a very long time but it does happen due to the high pressure and the microscopic gaps that become larger with time and hardening of the rubber in the o-rings.
Using people's lack of experience as proof for your statement is circular reasoning that proves nothing and using absolutes only makes your statement weaker, because you admit the very reason why systems eventually need to be refilled: because they eventually leak.

 

I never said that refrigerant couldn't leak! Sure it can, but it is unusual for most car makers to have their A/C leak refrigerant even after many, many years of use. Ford products have had inferior O-rings (seals) for many years, which are known to leak refrigerant. Most vehicles do not leak refrigerant, thus there is never any need to evacuate and refill, replace or top-off the refrigerant. It is not unusual for older vehicles (10-30 years old) with hundreds of thousands of miles on the odometer to have their A/C working perfectly with the original refrigerant.