My Subie's air conditioner has never needed attention.

While it still puts out cold air, it's not as icy cold as it used to be....noticeable a while back when we had a few days of 90+F temps.

It likely has lost a bit of refrigerant over time, so I'd like to top it off with some HFC-134a to bring back maximum efficiency.

Having no experience with dealing with ACs, and not wanting to run into trouble due to improper technique or procedure, I'd like to know the proper method for adding refrigerant.

There are two valves in the tubes going from the ac compressor, each covered with a blue plastic screw-on cap. I'm assuming that refrigerant is added via one of them.

Could anyone give me the "short course" or point me to one? I'd be much obliged.

read up on the internet about this, lots of good information you should know. you need to know what kind of refrig your car has and some basic stuff. assuming you read and get a basic understanding:

 

as a quick do it yourself check before doing anything, unscrew both of the caps and look down in them. if either one looks wet then you just found your system leak - the shrader valves are leaking. you can tighten or replace them. although replacing them requires a special tool that can pull them out and insert another one without releasing coolant.

 

on to refilling yours:

 

buy a can at any auto store that already has the adapter on top. it will only fit one of the two fittings you see - that's the one you use (of course!)

 

turn the car on and the a/c all the way cold and the highest fan speed setting.

 

follow the directions on the can (like shake can, don't turn it upside down, etc) and hook it up to the port that it fits (remember it only fits one, real simple)

 

keep adding until the a/c gets cold inside (might help to have a helper)

 

do not keep adding refrigerant...more is not better....unless you like dangerous situations and expensive repair bills.

 

i'd get some with the "system sealer" in it for good measure.

Use a thermometer of some kind, dont go by a helpers sense as to what cold is.

 

 

nipper

i'd get some with the "system sealer" in it for good measure.

 

 

Suggest going easy on any "system sealer" product. Yea, maybe a little is okay, use more and your are likely to seal up the internal tubing in the condensor or evaporator. I did that only once, and learned my lesson.

I would avoid the sealer and add a little R134 with die and try and find the source of the leak. Stay far away from the sealer!

Ok, if I use a thermometer, what would be the lowest temp readout at a dashboard vent that I should go for.

Since overcharging would lead to ac trouble, I figure I would add refrigerant a little at a time until the ideal temp is reached. I'm thinking about 41˚F with the thermometer inserted into the vent. Does that sound reasonable? Or is that pushing it to far?

Thanks for the urls, nipper. The article at aa1car.com states that one can use a low pressure gauge when adding refrig. I might get one of those, or one that comes with the refrigerant.

25-40 lbs pressure is what to go for. So if I add refreg 'till the qauge read 40 lbs, I will have charged the ac system to maximum efficiency. Hmm, that sounds like the way to go.

Don't charge it to 40, you could overcharge the system. Best thing to do is get a set of manifold gauges so you can monitor the high side pressure, should be about 150-200 depending on ambient temperature.

 

Overcharging the system can damage the compressor, and they run about $400

 

You should be good with a low side pressure of around 30 lbs.

Harbor Freight has gauges on sale right now for under $40

 

Great way to check both hi and lo sides at the same time - the only "problem" is that adding refrig is a "can at a time" thing (you can stop the fill if you need to stop it, but you will lose the rest of the can)