Bleeding air from AC - possible?

Z06C5R · 06-10-2008, 10:52 AM

So now that I've figured out how I'm going to get my AC ready to charge, I need to determine if I can charge it myself or not. The system is currently completely empty (suspect it was evacuated as part of an unfinished 134a conversion by PO). Obviously I can't just hook into it and charge because of all the air in there... I know the pros run a vacuum through it to remove air, but I was wondering if it would be possible to effectively bleed the air form the system by opening the hi-side port while the low side it taking on coolant, thereby giving the air somewhere to escape to? I'm sure it won't be as effective as running vacuum, but perhaps it could at least get me headed in the right direction so the pro-shop bill isn't so huge?

If not, can I possibly rig a mighty-vac to pull the required vacuum, or no?

John_AZ · 06-10-2008, 11:42 AM

The least expensive way is from www.harborfreight.com.
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=96677
Not all AC mechanics would approve of this method.

They also have the guage and hose kit for $43

John_AZ

mikepellegrini · mikepellegrini's Garage

The problem is that that type of pump doesn't pull a heavy enough vacuum to really work. Gotta have all the air and moisture out... or so I was told by an A/C mechanic.

Z06C5R · 06-10-2008, 01:15 PM

Yeah, I thought there was no easy way out, lol. The problem is, mechanics always like to do everything the most expensive way possible, so I know they gona want to do a whole system analysis and find all kinds of problems and replace all kinds of stuff... I mean, a long lasting solution to AC problems is great, but if I had 1k to spend, I'd be putting it into go-fast parts for my Z, not this.

fast924S · fast924S's Garage

Well you need a pump that can pull up to -30 inchs of mercury. The thing with AC is there is no really cheap and correct way to do it. ANY AC place is gonna pull a vac and hold it for approx 10min to check for leaks, then they are gonna fill it for you and check for leaks again. They might tell you to replace stuff or whatever but just because they want to doesnt me you HAVE TO. As far as AC goes, everything has to work right for the ac to be cool and last. DO it once and do it right.

I myself went the cheap way with the 2 70 AC, (2 windows down at 70 mph lol) I removed my system so I could spend more money on go fast stuff rather then waste it on AC repair.

mattdavis11 · 06-10-2008, 03:54 PM

My summer gig is a/c work, and my shade tree mechanical capabilities got me the job, not that I wanted it, but I'm not doing anything else right now so why not. My best leak detector is soapy water and putting air INTO the system. Nitrogen will work too. If you don't have compressed air or nitrogen, it's going to be hard to do. I only do this to find the leaks where I can't visibly make an assumption. Some of you may have leaks.

Having said that, you can get cold air without vacuuming the system down, but it will not be as cold.

If you can't get a whole can in, then you might try jumping the low pressure switch to help things along. Once you have one can in, there should be enough for the system to allow the compressor run.

If you had leaks, you are going to need to add oil to the system. Do not mix oils, this is not good, if you had ester in there put ester back in there, if you have pag, ditto. Since there is no way of knowing exactyl how much oil escaped, just guess. Some is better than none. 2 ounces is a general rule for a pretty good leak, no oil is asking for trouble.

When charging the early car system you will want to put in no less than 2 full cans of r 134. I put 33.5 ounces of R134 and 2 ounces of oil in. If you are doing Freeze 12, the can says 10% less than what is required for R12 (which is approx 40.6 ounces of R12 refrigerant). Ambient temperature makes all the difference, to dial it in, you must have guages. I put in 83% of the R12 capacity, I used 134 and it blows damned cold, but mine is done the right way, which includes finding all the leaks and vacuuming it down. You can do the drier and expansion valve if you want, I did not, but then again there was no trash in my system, my compressor did not lock up, the front seal did leak though. If you know your compressor blew chunks, find a new or rebuilt unit. My guess is that out of 10, there are 9 that have a front seal leaking, 4 probably have a bad electrical clutch.

Like I said in another thread, mine has been good to go for several years.

Let me know if you have any electrical problems, I've been through it, and have several ideas as to what it might be.

Z06C5R · 04:08 PM

I run 2-70 in the Z, lol. I honestly thought I could in the Porsche, but between the big glass hatch and being a lot more sealed up, I think it actually gets hotter in the well-insulated (relative to the Z, at least) Porsche. Then of course there's the mental side of it, knowing that the AC is right there, but just won't work! But the big bother for me is that I just sank over $500 into all new stereo equipment, and it's very annoying not to be able to fully enjoy it.

Matt, it looks very much to me like at least the dryer (haven't looked at the expansion valve) has been replaced, as it looks oddly new and shiny compared with everything around it... Between that, the existing 134a hi-side fitting, and the system being totally empty, I have to guess someone already tried the conversion, got to the low-side port and gave up, LOL!

On a semi-related note, has anyone had good luck with reducing interior temps with tints? For sure it's not as good as AC, and probably just as expensive to get done, but maybe between more efficient glass and a semi-complete AC overhaul I'd be ok to leave the windows up?

fast924S · fast924S's Garage

Tints are cheap, compared to some AC repair, Good tints, Proly like $200 installed. Where in CT are you from????

mikepellegrini · mikepellegrini's Garage

I had my windows tinted and it only cost about $250 with tax. Looks cool as all get out. But doesn't help the temps at all...

It's a black car and without A/C, I'd be dying in the summer...

WaA420 · 06-10-2008, 08:00 PM

Does everyone understand why it is important to pull the system into a vacuum?

It serves several reasons such as removing moisture and getting all non-condensibles from the system. Don't bother putting any refridgerant in the system unless you do it correctly.

hpservertech · 06-10-2008, 08:54 PM

Obviously not. My opinion...do it right or do it again and again, spending more money and time.

Just find a job that will do exactly what you want them to do and pay them for it. Any shop that does AC work can do this.

Z06C5R · 06-11-2008, 01:53 PM

I don't deny that I'd certainly have to do it again if I tried to do it half-assed on my own - It's just that it was unseasonably hot the last few days and I was desperate to get cold air - even if it was only for a few days, it was worth the price of a couple charge kits to me.

Fast, I'm in Marlborough - 'bout 20 minutes south of Hartford.

88BlueTSiQuest · 06-11-2008, 02:33 PM

Quote:

Originally Posted by hpservertech

Obviously not. My opinion...do it right or do it again and again, spending more money and time.

Just find a job that will do exactly what you want them to do and pay them for it. Any shop that does AC work can do this.

I agree. I'll tackle any job on my own, but when it comes to charging and maintaining an A/C system, then it's up to the pro's.

My Altima is about to go in to fix the air, it had a leaking discharge hose, I ordered the hose to save money, but I'm not going to install it. I'll let the pro's re-claim any left over freon, then they can change the hose, vacuum it out, and charge it back up.

Not worth it to DIY, IMO.

mattdavis11 · 06-11-2008, 03:00 PM

Quote:

Originally Posted by hpservertech

Obviously not. My opinion...do it right or do it again and again, spending more money and time.

Just find a job that will do exactly what you want them to do and pay them for it. Any shop that does AC work can do this.

I sometimes wonder about other shops. I had a younger guy, maybe 22 come in on Monday, his 92 acura didn't blow cold air. I had been told that he wanted a full job. Compressor, drier, condenser, lines, hoses, evaporator, expansion valve, o-rings, retro to 134, everything. Well, come to find out that his shop, which his family had been using for 30+ years, had told them/him that it needed everything done, the compressor was locked up, trash in the system, yada, yada, yada.

We got the job because we undercut anybody, no make that everybody.

His shop had blown smoke up his ass. He was missing both schrader valves, and had one bad o-ring. I retro'ed his car and charged him up. The compressor was very quiet for a 16 year old car and it now blows cold air.

I even had to talk to his dad (on the phone) when he picked the car up an hour later. When I spoke with the gentleman, I let him know that I would do anything that he wanted done, but there really wasn't a reason to sell him new parts that he doesn't need, and in my opinion, he is good to go for quite awhile. I didn't mention anything about the other shop to the customer or his father. They are entitled to their opinion.

Anyway the lesson to be learned is....... check the financial status of your mechanic before you bring the car in.