AC Problem

[RiverDog]

I have a 94 aspire and while pitting the engine in last fall I hit the AC condenser, putting a hole in it. I never replaced it till about a week ago. I know the system needed pumped down before you fill it, so I bought a cheap vacuum pump at Harbor Freight. When I went to use it I found it didn?t come with the hose to connect it to the car. With living in the middle of nowhere, (40mile trip to any kind of auto parts), and $4.00 gas, I decided to just use the one can of R134 I had and try to get it into the car anyway. I figured it would at least be a little bit cooler then no AC at all. The temp was running in the 90?s lately. The gauge that come with the Freon showed the pressure in the high range after I put the can in and the AC really didn?t seem cool at all.
My wife talked to a guy who owns a little gas station near the house and he was going to draw down the system and put in the other can of Freon I had. I told her if he could draw it down I could handle the rest ok. She said he would go ahead and put it in since it would already be there. OK no big deal? I thought. On her way home she said she heard a pop and smoke come out from the hood. She took it back and he told her the compressor clutch had gone bad. Ok it?s a 94 and shit happens. He was to get one from a junk yard and install it. I just got a call from her asking how to hook up MY vacuum pump, it seems the guy doesn?t know how to do it. That tells me he never drew the system down to begin with or he never would have been asking how to use mine. He put Freon in from his own equipment and not from the cans she gave him so I assumed he knew what he was doing. This is why I normally do ALL my own work. I told her just to bring the car home. My question is, if excessive Freon was put in the system, what would have popped? Is there a safety valve on these cars? What should I be checking?

 

[Pacfanweb]

1. If that system has been open for any amount of time, much less since the fall, you cannot just replace the condenser. You also need to replace the accumulator, also know as the receiver/dryer. That's a must when you open the system.

2. If he used his own equipment, why didn't he pull a vacuum on it? You ALWAYS pull a vacuum on a system that's been opened.

3. If he overfilled it, what popped was the pressure relief valve. It's not a big deal....it's there in case of a situation like this to prevent something else from blowing. What you described is exactly what would happen if your pressure relief (some call it the pop off valve) blows off some refrigerant......a honking, loud noise under the hood and lots of smoke, which is the refrigerant. It'll blow off as much as it needs to to get the pressure down to an acceptable level.

4. Unfortunately, that symptom is also what you might see if the compressor or pulley locked up. Easy to diagnose...plus it usually smokes the belt off.

If you're lucky and all that happened is the relief valve blowing, do this: Replace the accumulator. Go ahead and replace the orifice tube, too. Then suck it down for at least 30 minutes. THEN charge it.

 

[RiverDog]

That's exactly what I was hoping to hear. I didn't know about the accumulator so I will replace that and the orfice as well. Hopefully the auto parts cary that stuff. From what she told me I don't think this guy has a clue. I did look under the hood last night and the belt was intact. Thanks for the quick reply!

 

[RiverDog]

Would there be another name for the orfice tube? I'm looking on auto zone and I don't see that listed.

NM found it on Rockauto.

 

[boomerang]

You may need to add some refrigerant oil also. You need to replace what would be lost when replacing the accumulator.

The overpressure pop-off would have resulted in some lost oil too. You might get away with not adding oil just replacing the accumulator, but when combined with the overpressure situation, well, I'm not sure. What do you think Pacfanweb?

Recharge the system by weight. Don't just throw a couple cans in or whatever. The refrigerant container will be marked for weight. There should be a sticker under the hood telling how much refrigerant the system holds. Also, allow it to be drawn in from the top of the can. Turning the can upside down to make the job go faster is risky in that it's possible to slug the compressor.

It's a common misconception that there's not a lot involved with an A/C system. It's just not true.

 

[RiverDog]

Originally posted by: boomerang
You may need to add some refrigerant oil also. You need to replace what would be lost when replacing the accumulator.

The overpressure pop-off would have resulted in some lost oil too. You might get away with not adding oil just replacing the accumulator, but when combined with the overpressure situation, well, I'm not sure. What do you think Pacfanweb?

Recharge the system by weight. Don't just throw a couple cans in or whatever. The refrigerant container will be marked for weight. There should be a sticker under the hood telling how much refrigerant the system holds. Also, allow it to be drawn in from the top of the can. Turning the can upside down to make the job go faster is risky in that it's possible to slug the compressor.

It's a common misconception that there's not a lot involved with an A/C system. It's just not true.

Just a compressor, condenser and some tubes... Until you look at the parts listed. I am very mechanical, I've rebuilt engines, transmissions, etc on cars, trucks, boats and motorcycles. I've never did more than add a few onces of freon to anything till this came up. i didn't realize all that's involved. I'm sure I can handle the work, just didn't know where to start checking. I really appreciate the heads up on the fix, thanks

 

[boomerang]

Just to add to what's been said, you're going to need a vacuum pump and a set of gages.

The mechanical part is no big deal.

Replace the orifice tube first. Once you've uncapped the new accumulator, get it in place in the system with the hoses attached as quickly as is reasonably possible. There is a desiccant inside that attracts moisture. You want to minimize the amount of moisture the desiccant absorbs. The reason you need to replace it is because it has been exposed to the elements while the condenser was damaged and it has become saturated with water. No amount of vacuum will remove that water.

Then attach the vacuum pump utilizing the gage set. Draw the system down with as much vacuum as the pump will draw. Isolate the system using the gage set, and turn off the pump. As was said, make sure the system will hold vacuum for at least 30 minutes. If it won't hold vacuum, it won't hold refrigerant. (In reality, it still may not hold refrigerant. Just because the seals and O-rings hold vacuum, there's no guarantee they'll hold pressure. This fact is the bane of all A/C techs.)

If it holds, ready your refrigerant can(s). Attach the hose to your can. The hose you are using has air in it. With the valve cracked, bleed the air out of that hose at the gage set till refrigerant comes out. Be very careful. You can get frostbitten in a heartbeat.

Then crack the appropriate valve on your gage set, and with the engine running and the A/C on, slowly add refrigerant. Somewhere during this process the compressor clutch will engage. This is a good sign. (The system has to have a minimal amount of pressure in it for the clutch to engage the compressor.) Repeat the process until the system is full. If you're lucky, the system will hold, say, exactly two cans. If not, you're just guessing, as the only way to tell if you've added the proper amount is with a scale.

If you can lay hands on the proper pressures, both high side and low side, you can fine tune the refrigerant charge using the gages. You'll need those figures and the corresponding chart to know what pressures you should be looking for to compensate for the outside temperature.

The fittings on the gage set are idiot proofed, but make certain that you add refrigerant to the LOW PRESSURE side of the system.

I used to have a certification in A/C work, but, it has been nearly three decades since I've worked on an A/C system in this capacity. I don't think my memory has failed me. The principles of refrigeration have not changed, that's for sure.

 

[Pacfanweb]

Boomerang, yes, I agree that he should add a bit of oil to the system. Not much...an ounce or two will do, I think.

The car should have a sticker under the hood somewhere that tells you how much refrigerant to put in. If not, you can charge it by pressures on the gauges, like Boomerang has outlined.

VERY generally speaking, at least around here in the hot summer, I'd add refrigerant until my high side was just over 250 and the low side was near 40...if you live in a very hot region, you might not get the low side that low, but as I said, these are VERY general numbers. The good news is, if you accidently overcharge it, you already know your relief valve works.