97' Impreza Outback A/C blows hot air

[palfer]

Well after 15 years I finally have a problem with my A/C. I've done a multitude of different repairs on this car over the years but one thing i have little experience with is A/C.

 

From what I've read it's likely a leak and the culprit more often than not are the O-rings on the compressor. I could start there but was hoping someone could give me a stepwise diagnosis procedure for getting to the bottom of this.

 

I do own a set of gauges, bought them new about 6 years ago and have never taken them out of the box.

 

thanks for any help!

[porcupine73]

Well normally I think what people do is put some dye in the system, then you use a blacklight to pinpoint the leak source. Subaru has mixed feelings on using dye in their a/c though. If you suspect an o-ring, you can get an o-ring kit pretty cheaply and just do them all, it's not that difficult. At this age it's not a bad idea to put in a new drier too, especially since now it probably has air in the system. A good vacuum at warm temps is best before recharging to boil off moisture.

[nipper]

Sometimes it just pays to bite the bullet and take it to a shop. the cost of refrigerant to refill the system fomr an autoparts store, it may just be cheaper for a shop to do it. A good shop recycles the refrigerant and tops it off as opposed to using those little cans.

[avk]

I'd just top it off, using one can with added dye and the rest without (too much dye = bad), and see how long it lasts (instead of harming the environment by driving to the shop and back!).

[palfer]

OK. Found the leak (o-ring at compressor), replaced both rings there. Now for next steps I have some questions:

 

1. Do I change the receiver now or vacuum down with old receiver for leak check?

2. How long should I vacuum down and to what level?

3. Once I achieve appropriate vacuum. Is some drop the vacuum level OK so long as it maintains "vacuum" or should it stay pegged?

[CoupedUpSubie]

Once you open the A/C system (or any system using refrigerants) it needs to be pulled down extremely deep to remove as much moisture and air as possible. Most shops will pull down 29 inches of vaccum(almost perfect). This will allow the system to operate at full capacity and for much longer.

 

Short answer: Unless you have your EPA 609 certification and the proper equipment, take it to a shop. If you have no idea what a EPA 609 cert is then take it to a shop.

[porcupine73]

I will jump in on 2 and 3

2. How long should I vacuum down and to what level?

3. Once I achieve appropriate vacuum. Is some drop the vacuum level OK so long as it maintains "vacuum" or should it stay pegged?

 

How long you need to vacuum depends on the vacuum level (i.e. using a refrigeration vacuum pump) and mostly the temperature. There's charts out there that will estimate how long you need vacuum. If it's say 70F I think overnight is more than adequate. If it's much below 60F it can become much harder to get the moisture to boil out. It takes so long because even if you get the moisture to boil, it travels toward the vacuum pump only extremely slowly, so it takes a long time. So you can't just pull a vacuum, close it off and think that is going to do anything. The vacuum pump must remain connected and turned on.

[idosubaru]

i would leave the receiver. Subaru a/c systems are extremely robust and have very few issues. i work on them all the time.

 

Subaru A/C is really easy to work on yourself, they are robust and have few issues. you can easily recharge yourself. you don't have to take it to a shop, you don't even have to pull a vacuum. if you charge it as is I wouldn't be surprised at all if it serves you the rest of the life of the vehicle.

 

if you want perfection pull the vacuum and charge it.

 

if you're going for the whole vacuum pulling and all that - i would go ahead and at least replace the orings around the radiator area fittings, or just every other oring you can find in the engine bay. really only the ones around the radiator are brittle. the ones by the firewall are almost always in okay shape...but not a bad idea to replace them while it's all apart. you can replace another 3-5 orings really easily now, might as well.

 

I've never worked on other makes, but i've done tons of Subaru A/C work and they're cake walk. can easily avoid the shop if you need to on Subaru's.

[palfer]

Thanks for the input. I already bought the receiver and have a vacuum pump so might as well go the distance. My question is once pull a vacuum 28 Hg and shut down the pump. Should the vacuum level stay pegged at that level or is it normal for it to creep down a bit to 22ish or so over the course of an hour or so.

 

Or is that creep indicative of a subtle remaining leak somewhere?

[idosubaru]

what does it do after that hour...does it stay at 22psi then?

 

not sure if different pumps/gauges could differ but i'm not surprised to see some creep due to equipment, disconnect, or internally equalizing. i've never looked that intently - i just pull the vacuum and charge. well, actually i'm almost in the habit of not even pulling vacuum or using my gauges Subaru's are so easy, so far i'm batting a thousand and the a/c works just fine for here. all three of my current daily drivers are running without vacuums being pulled and have been that way for years and i even have a vacuum pump and gauges. LOL

[palfer]

It was the O-rings at the compressor. Changed them at the condenser and changed the drier as well. Charged and she blows very cold now. thanks for the advice.

 

One more question:

 

The clutch is a little sluggish when trying to engage, spins slowly then eventually catches and does its thing. Anyone know how to adjust the clutch on the compressor? From what I understand, its done manually as opposed to newer vehicles which are hydraulic.

 

thanks