2000 VW Golf TDI Air Conditioning

[davevw]

Working on a friend's VW Golf.

About a year ago, her AC needed a little bit of a top off on the AC. That went fine and worked great until a week or two ago. We assumed it had lost a bit and would probably need another top off.

Well she brought it over and with the engine running (at both idle and at about 1500 RPMs) I was seeing ~90 PSI on the low side and ~150 on the high side. When the car turned off, the pressure went up, but that kind of makes sense as the lines were heat-soaked from driving.

Any ideas on where to go from here? She's a partially-disabled widow, so money is always kind of tight; hoping there could be something not too expensive I'm missing.

[Cornbinder89]

I think we have run into this before and it is the control valve in the compressor. They are known to get stuck. Some replace the whole compressor others just the valve. By replacing the whole compressor you are sure that it isn't a mechanical issue inside the compressor that is preventing it from going to high output, but the cost is much more.
Anyway you look at it, you have to evacuate the system, and depending on where the compressor is located, pull it to gain access.
It will not be a few dollar job no matter what.

[davevw]

Thanks. I did something similar with my wife's car (a Kia) about a year ago and wondered if it may be the same issue here.

I never let her pay me for small stuff (like hooking up my gauges and checking into things last night or oil changes) and charge a whole lot less than for hourly labor than anyone else would cause I'm mostly doing it for fun and to help someone.

Seems like the labor would likely be the same, here, whether it is the valve or the compressor. (Well, slightly more labor to open the compressor and swap the valve, but at that point it seems negligible. But it appears there would be about a $200 difference between just the valve and a whole compressor. Luckily for her, we're getting close to the end of the really hot stuff, so I suppose there is some time to save up before next summer.

Sidenote: I'm sorta interested in a recovery system. Right now, to recover what is in anything, I'd need to take (or have her take) the vehicle somewhere to have the refrigerant recovered. Unless, of course, the car also developed a leak. But I don't like that. That, of course, would cost her more money.

Additionally, I'm a hobbyist and like to do as much of my own vehicle work as I can. And I dream of adding AC to both of my old VW Buses. (One of them came with factory air, long crapped out, but I saved the under dash unit.)

So, it kind of seems that being able to recover would be nice. Just looking around ebay, looks like I could pick up a used smallish portable unit and a tank. Would there be anything else I'd need to get to do this? Any recommendations on ones to look for OR avoid?

[Cornbinder89]

It depends on what you want to do with the "recovered" refrigerant. You can go as basic as buying a recovery tank and an old refrig compressor to suck the stuff out and turn in the tank when full. If all you are working on are small (under 4 lb) systems, you don't have to cool the discharge much (a little bit of copper tubing) and your ok. If you want to do big systems quickly, than a full recovery system with condensing capacity are needed.
If you want to recycle the refrigerant back into the system after repair, than a much more complex system is required.
To be fair, my refrig compressor and tank method will not meet the requirements of the EPA for draw down, but will come close, most all the refrigerant will be pulled from the system
Long before it was required, I used that method with a BBQ propane tank, the problem with the BBQ tank is the refrigerant is contaminated and can't be re used or recycled. Sub in a refrigerant recovery tank, and you can turn it in as pure 134a (if that is the systems you are working on) just don't mix refrigerants in the recovery tank.
So, to be clear, there are recovery machines that just remove the refrigerant and store in in a recovery tank, and there are recycling machines that suck it out, run through a bunch of filters and than you can re-use the old, recovered refrigerant as you would new. Big difference and big difference in price.

[davevw]

Ok, gotcha. So if I recovered refrigerant and held it in a tank, and just waited until I filled it up, then is there a place that would buy it or something?

I guess I assumed if I recovered it into the tank, then I could probably use the same machine to return it to the car. (Or, maybe just hook it up to the car's system and let the car suck it back in, sort of like how the small cans from the FLAPS work.) Is that an incorrect assumption? Thereby reusing most of the refrigerant.

[Cornbinder89]

Well I can't answer what would be involved in turning it in. those that would take the stuff want to be sure they are not getting a mux of refrigerants or contaminated. I have never looked into it.
The problem with taking stuff out and putting it right back in, is any moisture, acid or other problem will remain after the repair that caused you to open the system to begin with.
It is why you'll often hear people say use new when going back.
Refrigerant recycling machines have a bunch of filters and oil separators to leave the refrigerant equal to new, and the cost of the machines don't make sense unless it is your stock and trade day in day out.
I use my "old stuff" when I want to pressurize and look for a leak, but I know the backstory on the stuff as I only work on my own stuff.

[davevw]

Gotcha. Seems it isn't quite as simple as I imagined. Never is! So you're mostly using the old stuff to pressurize, then recapture and fill with fresh?

[Cornbinder89]

Yes, but I don't do it much. The reason you can't just use an old 30 lb keg for capture is there is a one way check in the stem of the keg that you can't remove.
With any pressure tank, you must be careful not to fill over 75% full or it will explode when it gets hot, The recovery tanks have a over full protection, but old BBQ tanks and 30 Lb kegs do not.
Whatever tank you use for capture must have enough volume to allow the compressed (and heated) gas to expand, or you need to cool the gas with a condenser before it flows into a small tank. 30 lb keg size is enough volume if you are not storing 30 lbs of used gas, the hot gas will enter and cool and the pressure will not get too high.
The reason you can't cut the valve off a keg and weld a new valve without the check on, is unless you are able to hydrostatic test your tank and weld you could be making a bomb that could kill you if the weld/tank failed under pressure.
Pressure vessels are a benign looking thing that can fail and become very dangerious.

[Cusser]

I dream of adding AC to both of my old VW Buses. (One of them came with factory air, long crapped out, but I saved the under dash unit.)

I'd contact either Gilmore in Las Vegas or ICE AC in San Diego about a kit for your VWs.

[Cusser]

I have used my vacuum pump and a small canister no longer needed by my workplace to recover R-12. Nowadays, I'd have to buy dry ice to do this, I'd use surplus from work back then, and use waste alcohol from the lab. Something like this:


Here's what I'd do. I installed an AC fitting to my canister. I pulled vacuum on the canister to remove any remaining refrigerant or air, then close its valve. I'd put the canister in the freezer. Then I'd put the canister in a dry ice-alcohol bath, attach the canister to the vehicle AC, open the canister's valve, and its vacuum would start to pull over refrigerant. As refrigerant arrived into the cold canister, it condensed into liquid refrigerant, so still was under vacuum, so more refrigerant came over, etc. When complete, I'd shut the canister valve; when filling, I'd just fill from the canister. I'd weigh the canister before and after so I'd know how much refrigerant was recovered, and label whether R-12 or R134a.