a/c system diagnosis: Grassroots Motorsports forum: Grassroots Motorsports Magazine

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March 2, 2009 7:26 p.m. Brust New Reader

Any smart guys out there on a/c systems? Here's what I've got: 2002 Subaru WRX wagon. Made a whooshing noise for the last couple months when a/c was turned on. Now a/c doesn't work: No cold air. Clutch won't engage when I turn the switch on. I've checked the fuse and it's good. The high pressure compressor outlet hose had oil all over it. The compressor spins freely when I move it by hand. The other hoses look clean and dry.

Am I right to assume that it's probably just a bad outlet hose?

How important is it to vacuum down the system if I were to replace the hose? I don't have the equipment to do this, but am a VERY diy type guy and don't want to pay $80/hr for what I can do myself.

Ideally, I'd like to buy the hose and recharge kit myself and do it, but wanted to consult "my corner" before wasting a bunch of money.

Thanks as always for the help and advice.

Brust
March 2, 2009 7:44 p.m. internetautomart SuperDork

you have no choice on placing the system in a vacuum, that is part of how the A/C system works.
Talk to a local shop and see if they will do a leak test on it. Back in the day we would just toss the refill in with some dye and see where it leaked out from that.
Yes it is a pretty safe guess that it is that hose, but I'd rather know for sure before spending my money on it. I prefer to spend money on a diagnosis than throwing parts at something.
March 2, 2009 8:25 p.m. foxtrapper SuperDork

Vacuuming down the system is to remove all air contamination. Air doesn't work well in an a car's a/c.

So if your current system still has pressure, it won't be contaminated with air. When you install the new hose, it will be.

This gets into how well do you want the a/c system to work. You can get by with just charging it, leaving the air that was in the hose, in the system. The a/c will work, just not that well.

Personally, I'd use it as an excuse to go buy yet another tool. Vacuum pumps are almost handy. The cheap ones ($15 on sale at harbor freight regularly) will not draw down a powerfull vacuum, so they don't get as much of the air out. But, typically they do a good enough job.
March 2, 2009 9:59 p.m. erohslc New Reader

The vac is to remove the air and the water. Water is death to A/C systems. The drier only has a limited capacity to absorb moisture.

Carter
March 2, 2009 10:37 p.m. shuttlepilot New Reader

I've been taken for a ride before letting shops service my AC. After replacing parts that didn't need to be replaced and misdiagnosis leading to the system not working again, I went and got my own AC tools and never looked back.

Servicing an AC system is not hard, its just that the tools and components are expensive. Some investment in tools for ac use will make life much easier and will allow you to work on these systems in the future. A system like this:

http://www.thetoolwarehouse.net/shop/MAS-91580-A.html

would pretty much let you charge and diagnose any car out there with the right charge specs. You really should have a recovery unit if you intend to ever discharge, but you can pay a shop to do that.

Depending on how long your system is open, the oil may be no good. The oil is partially a dessicant. You might want to go and empty it out of each component and replace it. You should definitely replace the drier and get new seals. When installing the new hose, get some of this stuff called nylog and apply it to your connections before reinstalling. This place has been helpful in getting parts and equipment: http://www.ackits.com

Also, when buying cans to charge your system, make sure it contains NO sealant or any other snake oils!!! Don't let anyone put any sealant in there. It is absolutely the worst stuff you can ever put in there. I can easily destroy any AC system or tools when things go wrong.
March 2, 2009 11:18 p.m. Brust New Reader

Thanks guys. You are reaffirming that I can do this myself. Shuttlepilot- Would it be offensive to ask if the HF tools would work as well as the more "professional" tools you linked? http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=92649 $50 for the gauge/manifold set, and $75 for the vacuum pump would put me in about $125 vice the $475. I can also get a scale if I needed one.
I'm not going to do this for a living, and if I could get by with these tools for the few times in my life I plan to do the job, I'd be happy to save the $300. On the other hand, if the quality of the vacuum pump or gauge set is that important, then I can probably swing it. After all, I'll probably at least break even from having someone else do the work.

Thanks again. Brust
March 3, 2009 6:24 a.m. ignorant SuperDork

I have the HF vac pump and set of gages, they work.
March 4, 2009 12:53 a.m. shuttlepilot New Reader

The HF stuff should be fine. I ended up getting a neato Imperial manifold that lets you do a liquid charge , costed alot but I hate waiting. Make sure you cap the ends and keep everything clean. The last thing you want is a clogged orifice tube.

Be aware that you still need other stuff like a refrigerant can tap and if you want to get really fancy, extra inline valves and a t splitter to switch between charge and vacuum. It's all in an effort to keep air out of the system. You can get the common stuff from thetoolwarehouse, but if you need to some of the more specialized fittings,FJC should have it

http://www.fjcinc.com/

You can guess by how many cans of refrigerant is needed, but doing it with a scale will help you get everything just right which is the key to AC efficiency. A 5 lb scale that can count grams will do. Make sure you account for the weight of the tap, hoses and can on the scale when you start charging. I got the pelouze 5lb postal scale and it works fine, just make sure you disable the auto off. Again, the Nylog is highly recommended. Make sure you get the correct type.

Hope everything goes well
March 7, 2009 12:53 a.m. Brust New Reader

Thanks for the advice- I'll definitely take it. I've got the HF stuff on order and will buy the refrigerant/tap locally. I think I'll need to do a little more research, but hopefully this is something I can pull off.

I almost felt bad asking about a/c in the middle of the winter, but it gets hot here in Hawaii!
March 7, 2009 1:32 a.m. driver109x Reader

+1 on ackits.com. Their forum was very helpfull. I got most of the parts plus the Mastercool manual to fix the ac on my BMW.