AC service questions. -2004 Legacy

[GunFunZS]

My car is a 2004 Legacy 35th anniv. H4, auto.

 

Prior owner was my brother. He tried to recharge AC with one of those cans, and probably messed something up.

 

 

I would love to redo the AC on a budget and have borrowed a dual gauge setup. As I understand things, you need to know the ambient temp, a high pressure, low pressure and measure the differential.

 

What I want to know is if there is a guide somewhere for full proceedure, and what those numbers should be...

 

If my brother blew a seal, then it's empty. I could replace all the o-rings, and purge out any oil, take it to a shop and have them do a purge and recharge. If necessary, I could replace the compressor too, first. I know that would probably cut about $400 off the bill for doing a simple task.

 

But before I do stuff like that, I want to see what is going on. i.e. does the compressor seem to work? Is there any refrigerant in the system?, etc.

That is what I am asking for guidance about.

 

Thanks.

[RustyRuu]

by the passenger side strut tower there is a silver cylinder that is connected to the ac lines, i believe it has a purple connector, unplug it, on the male side of the connector put a small piece of wire between the only two holes, a paper clip will work to.

 

this will tell you if you compressor clutch is cycling on when you connect them, also just plug in the gauges and see if you have any pressure in there first, if not its a leak, its usually the top hose going to the compressor , there are actually two seals there

[GunFunZS]

Thanks.

 

I will look at this and try to follow up. How much pressure should I see under load, etc?

[08SpecB_DE]

35-40 psi on the low side

200 on the high side- higher if it's really hot

[Infosecdad]

It's easy to overcharge those if you aren't paying attention, then it acts like it's empty and won't turn on because the pressure is too high.

[apexi]

This may be obvious, but if you're just checking pressures, make sure the two knobs up by the gauges are closed tight before hooking them up to the low pressure and high pressure ports.

 

I'm a newbie to AC stuff, but I did learn a bit after replacing my condenser last year. Ambient air temperature seems to be very important when checking pressures. In the factory service manual for 4th gens, they list the pressures when the outside temperature is 86F-95F I think, or something close to that. Not a bad idea to check for any oily residue behind the AC pulley, I think my car has a little leak out of the shaft seal there, I have to recheck after cleaning it up a week or two ago.

 

There's a lot of videos out there on AC stuff, but I like this guy, and he explains what you might expect to see with a low charge. To summarize, it may be overcharge if your low side and high side pressures are both high. Low charge if both low and high pressures are low.

 

Not a bad idea to have a way to check air vent temperature. I just got something like this at my local hardware store

https://www.amazon.com/Taylor-Precision-Products-Classic-Thermometer/dp/B00004XSC4

 

Sorry for the lengthy reply, but I just decided to look up the 2004 service manual to see what they say the AC pressures should be. Going off memory, it seems like the numbers are the same as for 4th gens, or damn close to them.

 

1. Place vehicle in shade and in a windless condition.

2. Connect manifold gauge set.

3. Open front windows and close all doors.

4. Open hood (obvious, I know, but I was going to copy the instructions verbatim and changed my mind)

5. Increase engine speed to 1500rpm

6. Turn on ac to max cool, recirc on, blower set to high.

 

low pressure 127-196kPa, 18-28psi

high pressure 1,471-1667kPa, 213-242psi

Ambient temp 30-35C, 86-95F

[YeuEmMaiMai]

not sure of the charge level? draw the system down and if it holds a vacuum, then recharge with proper level of r134a. most common area of leaks on a Subaru are the compressor seals