Air conditioning rant and a few questions

ToddA1

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Tony,

I was attributing the lower pressures to the cooler ambient temperature. I guess I'll be adding some 134a.

So you're seeing your pressures continually rising and falling, too? I'm seeing them cycle every few seconds, not minutes.

-Todd
 

TonyJetta

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It takes ~1.5 min to rise to 245 then the fans come on & pressure falls to 200-205 when the pressure rises again.

41oz is near the max fill. IIRC, 1150+/-50gram = 40.5+/-1.75oz

You could go for another ounce.

When you originally installed the compressor and associated parts, did you divide PAG oil among the components? Also, what PAG oil did you use?

Tony
 

ToddA1

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I figure I'm close with the 41oz. I didn't factor for the 6' hose displacement, though. I guess I'll add and try and figure out the rapid fluctuation if it continues. I really don't want to be starting a warranty claim.

The last time, I didn't put any oil in the evaporator. Adding oil to everything never really made sence to me. The compressor is the only thing, other than maybe the TXV, that needs oil. After flushing everything a second time, the oil's dye was circulated through the entire system.

I used Super Cool DEC PAG 46.
http://www.supercool.ac/products/lubricants/pag-46-with-uv-dye-8-oz/

Pretty impressive comparison.
http://www.autoacforum.com/messageview.cfm?catid=20&threadid=17571

-Todd
 

TonyJetta

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Todd, keep in mind that the oil circulates through the system. That's why you want to put some oil in each component, so that the compressor doesn't push all the oil out before it starts receiving oil.

That's some interesting reading. I need to digest that a little more. Thanks for posting it!

Tony
 

ToddA1

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Hmmm.... I guess that makes sence. Im guessing (hoping) I'll be fine. I filled the compressor through the fill port and also put oil into the head via the suction and discharge port.

After I saw that thread, I decided DEC PAG was the only oil that I'd use. Once moisture is mixed, you'll never get it out no matter how long you vacuum.

On another note, I hooked the gauges up to the car this morning. Both sides were showing around 70 lbs. static. I'm hoping it was because it was below 60°. I'm having a difficult time thinking that a leak would suddenly appear.

Turned the ac on and noticed that the hunting pressures also disappeared. I still put 2 oz in, and the high side never got past 150psi. I put soapy water on every connection I could reach and saw no signs of leakage. Air was still blowing the same as yesterday, so I'll recheck later.

This is getting old....

-Todd
 

tripl-e

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Recalcitrant AC System

I've read this whole thread and still don't understand how to judge whether or not an AC compressor is actually compressing. The variable displacement style compressor can be spinning but not compressing if the displacement control has effective displacement at or near zero. As far as I can tell the only diagnostic tool available to even roughly quantify this is the hi/lo pressure spread.

Todd, your compressor seems to work intermittently. When pressures are somewhere near 'normal' your system cools adequately; when pressures are out of range, naturally, the system does not cool adequately. I'd be curious about just how this compressor displacement control works and, more to the point, how to determine whether or not yours is working normally. And I'd REALLY want to know where that missing bit of reed valve is lurking ;).

After a compressor replacement (4 Seasons rebuilt) and thorough system re-fit my '97 B4 rolls down the highway blowing 38-40 F on 85 deg. days. I'd judge that 'normal' performance. The evaporator surface temp can't go too near 32 or you'll have an ice maker rather than an air conditioner. And most of the fun stuff that goes well with ice doesn't go well with automobiles in motion. Good Luck, its about to get warm in our neck of the woods!
 

TonyJetta

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Hmmm.... I guess that makes sence. Im guessing (hoping) I'll be fine. I filled the compressor through the fill port and also put oil into the head via the suction and discharge port.
I've only filled mine by pouring directly in the suction port, before installing the compressor.

After I saw that thread, I decided DEC PAG was the only oil that I'd use. Once moisture is mixed, you'll never get it out no matter how long you vacuum.
I found that claim interesting, too. I haven't had time to digest the information yet. Probably won't have time until the weekend.

On another note, I hooked the gauges up to the car this morning. Both sides were showing around 70 lbs. static. I'm hoping it was because it was below 60°. I'm having a difficult time thinking that a leak would suddenly appear.
Static pressures like that will follow the ideal gas law: PV=nRT

Since Volume, n)umber of molecules, and R the gas constant stays the same, you can directly compare pressures at different temperatures. i.e. P1/T1=P2/T2....

What is your static pressure at say 85F? Don't run the engine...that will heat the system just by being close to the heat source.

Turned the ac on and noticed that the hunting pressures also disappeared. I still put 2 oz in, and the high side never got past 150psi. I put soapy water on every connection I could reach and saw no signs of leakage. Air was still blowing the same as yesterday, so I'll recheck later.
This may be premature...I'm wondering if you didn't get a weak or flaky txv. It could also be the RCV in the compressor.

For reference, It's 100F right now, I'm getting 55-60F out the center vents with the fan on high (4). Going down the freeway this morning, ~75F, the center vent was 38-39F. Going home at 5pm, I expect to see ~52-54F on high speed. On 1 or 2, I should get down to about 44-48F. But that will take a few miles.

This is getting old...
Trust me, I know that feeling! This is the 3rd system I've installed on this car in 4.5 years of ownership!

BTW..One compressor I did install ALL 5oz of PAG oil into the suction side. At first I had no cooling. Then, I had what sounded like water hammer. I thought that was the oil circulating. After that, I had 40F air for the next year! Then the TXV went south, but I still had 55-60F vent temps.

Tony
 
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ToddA1

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As far as I can tell the only diagnostic tool available to even roughly quantify this is the hi/lo pressure spread.

Todd, your compressor seems to work intermittently. When pressures are somewhere near 'normal' your system cools adequately; when pressures are out of range, naturally, the system does not cool adequately. I'd be curious about just how this compressor displacement control works and, more to the point, how to determine whether or not yours is working normally.

Good Luck, its about to get warm in our neck of the woods!
I'm no ac pro, but I'm willing to get my hands dirty. Normally, I'd just be looking to make sure the clutch engaged and the hub is spinning. With that happening, you'd expect a new compressor to be compressing.

There's a link in here about the functionality of the control valve and the whole variable displacement thing. I understand it to an extent, but as mentioned, the manifold gauges are key.

I got as low as 50° on speed 2 on my lunch break. The ambient temperature was around 80° and the average vent temperature was 53°.... pretty lame.

I'm looking forward to the upcoming heat wave......


I've only filled mine by pouring directly in the suction port, before installing the compressor.

BTW..One compressor I did install ALL 5oz of PAG oil into the suction side. At first I had no cooling. Then, I had what sounded like water hammer.
Did you spin the hub of the compressor? It sounds like the compressor slugged. I spun my compressor hub with a drill for at least a minute.


Static pressures like that will follow the ideal gas law: PV=nRT

Since Volume, n)umber of molecules, and R the gas constant stays the same, you can directly compare pressures at different temperatures. i.e. P1/T1=P2/T2....
Huh?


What is your static pressure at say 85F? Don't run the engine...that will heat the system just by being close to the heat source.
We won't see 85° until Wednesday. I'll try and get it hooked up again, then.


This may be premature...I'm wondering if you didn't get a weak or flaky txv. It could also be the RCV in the compressor.
Geez, I hope not. If it's a leak, I can deal with that. I may just keep topping it off until Fall hits. I'm tempted to go back to propane or Envirosafe. I need to see my pressures first. Something isn't right.

-Todd
 

TonyJetta

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Did you spin the hub of the compressor? It sounds like the compressor slugged. I spun my compressor hub with a drill for at least a minute.
I only spun the hub by hand.

If you had prior pressure and temperature measurements, then you could compare them.

We won't see 85° until Wednesday. I'll try and get it hooked up again, then.
85F for a high temperature...we'd kill for that in AZ summers! Or wait until the monsoon hits, then enjoy the afternoon/evening. :D

Tony
 

ToddA1

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If you had prior pressure and temperature measurements, then you could compare them.

85F for a high temperature...we'd kill for that in AZ summers! Or wait until the monsoon hits, then enjoy the afternoon/evening. :D

I understand tracking the pressures to temperature, but that pressure formula was out of my scope, lol.

We'll be getting hit in a few days. We're expecting to see mid to high 90s by mid week. I'm not looking forward to that.

OK, so I'm a glutton for punishment. I went out, hooked up the gauges and saw 80 static with an ambient temperature of 71. I decide to add until the high side reaches 225psi. I ended up adding 2.5 oz. Either I have a leak or something isn't right in the compressor.

Cooling is still basically the same, maybe marginally better. Took it out on the open road, with the speed set to 2. I only saw a best of 49.

Here's a vid of the hunting. The low side fluctuates between 24-30 psi and the high side will follow. High side fluctuates between 210-220 psi.




After I shut it down and let everything settle static pressure went to 100 psi.

All this dicking around encroached into the time I had wanted to investigate that dragging rear caliper.

-Todd
 

TonyJetta

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According to the Bently:

  1. Static pressure at 77F = 81psi, when engine and AC system are at ambient temp.
  2. Engine warmed up
    1. 2000rpm
    2. Low side is within spec
    3. High side is within spec
    4. It's a graph, otherwise I'd give more specifics.
  3. The rest of that section talks about replacing the expansion valve if cooling is not satisfactory.
Let me know if this is cryptic and I'll try to make it worse! ;)


Tony
 

ToddA1

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A faulty TXV would show both pressures to be either high or low, in unison.
I'm wondering if you didn't get a weak or flaky txv.
The rest of that section talks about replacing the expansion valve if cooling is not satisfactory.

I was thinking back after I cleaned up. I think the hunting that I'm experiencing qualifies to the high and low in unison. What we think and what the Bentley suggests may be the fix.

Thanks for confirming my pressures are inline.

I wonder if I'd be able to feel anything if I removed he TXV cover and held the valve as the pressures are fluctuating? This part was an eBay buy and supposedly comes with a warranty.

-Todd
 

KLXD

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The Ideal Gas Law doesn't apply. You have a two phase system here, a mix of gas and liquid. You need a table or graph to determine pressure at a given temp.
 

TonyJetta

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The Ideal Gas Law doesn't apply. You have a two phase system here, a mix of gas and liquid. You need a table or graph to determine pressure at a given temp.
I was referring to a static system at equilibrium. ;)

Tony
 

Ski in NC

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I was referring to a static system at equilibrium. ;)

Tony
Does not matter static or dynamic. IGL does not apply. It's still two phase. There is some liquid laying around in there static. Static pressure will relate to the coolest temp area of the system and the saturation pressure that goes with that temp.

Watching those gauges looks like somewhat normal response to TXV modulating, but no expert here on these systems. What happens at 2000rpm steady? May need a brick on go pedal..
 

tripl-e

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I think the hunting that I'm experiencing qualifies to the high and low in unison. What we think and what the Bentley suggests may be the fix.

Thanks for confirming my pressures are inline.
-Todd
No question that with almost 200 psi differential between hi and lo sides there should be substantial heat being absorbed at the evaporator. At 80 deg. ambient and 200+ psi there should be plenty of liquid refrigerant at the TXV and at 30- psi there is plenty of room on the lo side to boil the plentiful liquid, but this apparently isn't happening. The TXV is what controls the 'boil' rate in the evaporator so that looks a likely suspect. If the compressor's displacement was not well controlled the system wouldn't maintain the pressures you're seeing. The hunting looks like the TXV spitting a little refrigerant into the evaporator and closing, spitting a little and closing, over and over. At a constant heat load the TXV would/should come close to a constant boil rate, matching the heat load. Looking more and more like a bogus TXV.
 

ToddA1

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Sounds like you know what you're talking about.... I'll have to agree with you, lol. The company I bought the TXV from is standing behind their warranty, so another is on the way.

I used the air on yesterday's lunch break and commute. It seems the addition of refrigerant helped. I was seeing slightly lower vent temperatures, but nothing great.

I wasn't crazy about the high pressures (and insanely low temperatures) that I was seeing with propane, so I'm thinking of doing a blend of the propane and r134a. My math tells me if I use 21 oz. of r134a and 8 oz. of propane, that should put me around the standard fill capacity of 41 oz.

I'm looking for some fittings that will allow me to charge propane through the manifold gauge set.

-Todd
 

ToddA1

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I finally got around to swapping the TXV, a couple deep vacuum sessions and a recharge.

I added 7 oz of propane and saw my vent temperatures dropping. I started adding the 134a and noticed the same low pressure hunting that I saw before. I stopped with the 134a after 5.5 oz., after seeing my high side around 275 lbs at 85° ambient.

I can't believe that another TXV is faulty giving me the same symptoms. I'm now leaning towards the compressor. I can't say for sure it was the propane, but I'll be sticking with 134a, after I get this warrantied.

-Todd
 

ToddA1

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I'm a glutton for punishment. I pulled another deep vacuum and tried getting my 55° vent temps back. I went from ok cooling to no cooling.

I had roughly 1.5 cans of 134a left, so I ran out and got 2 more cans @ $15 each. I started the charge and saw the low side hunting after the first can. It was rising and falling between 22-30 lbs, every 10 seconds or so.

After 1.5 cans I added the 3rd and saw no increase on the high side; it pretty much sat at 125 lbs with a 95° ambient temperature. I figured I should be around 175-200 lbs, so I called it quits; no need to waste the last can to get nothing out of it.

Advance Auto tells me Denso shows no availability on the compressor I need, so I'll have to keep watching the site for availability. They offered rebuilt replacements that carry the same warranty, but I think I'll try and hold out. They did offer me expedited shipping at no charge, so that was decent of them.

I'm considering buying a 30 lb bottle of refrigerant for about $140. I've spent quite a bit on individual cans.

-Todd
 

KLXD

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Gonahafta reread this thread. I've lost track of where you are.

Seems like you should buy a refrigerant recycling machine!
 

ToddA1

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I'm glad I've been updating this thread; I would have lost track of what I'd done, too.

In a nut shell, I've replaced the drier twice, the TXV three times, replaced the suction reed valve and control valve, flushed 2 times, added a high side filter, replaced the service valves, replaced the compressor with new, and evacuated and recharged many times.

What confuses me is that I lost all cooling by simply changing the TXV. The compressor now fails to build adequate high side pressure although it was never touched. Pretty coincidental... I'm almost tempted to put the old TXV back on, but being curious, I took it apart.

I called Advance last night and the remanufactured Tough One (4 Seasons) compressor carries a 2 year warranty, but it's also out of stock. There's also a Driveworks reman that got pretty bad reviews. Not sure I want to chance it, but it'd be $200 shipped after discount.

I'm hoping the Denso shows availability, this week. I'll have to see how long I can take the heat.

Doing the math, the 30 lb cylinder is the cheapest @ $5 per pound (pp). A 15 lb cylinder is $7.60 pp, 12 small cans is $8.33 pp and 6 small cans is $11.11 pp. I figure I've spent around $100 on r134a and about $15-$20 on propane.

I'm leaning towards the 30 lb cylinder, but haven't pulled the trigger.

-Todd
 

ToddA1

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Hooray, a compressor finally showed availability on the Advance Auto site so it was ordered this morning.

I ended up getting the remanufactured Tough One/4 Seasons compressor with the 2 year warranty. They gave me a good discount and free one day shipping, so i guess i cant complain. It should be here Monday.

I called Denso and the chance of me getting another was slim, unless I was willing to wait until the end of August as a best case scenario. I wasn't.

Anyhow, I was ready to buy a 30 lb of 134a, but I decided to do some research on the Envirosafe stuff. Mostly propane mixed with isobutane, although refrigerant grade stuff. Read some good, and some bad, but I stumbled upon something else that piqued my interest.....

Being an idiot and a glutton for punishment, I think I'll try it. I have to find a side can tap.

-Todd
 

tsquyres

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Todd,

Your thread makes me want to weep. I had been following this a while back as I have an 03 jetta that was having many of the same symptoms and ultimately the issue was charge volume related as I was too lazy to weigh out a proper charge from a 30lb bottle of 134. Now, having had to deal with ac issues on several cars and going through an unacceptable number of cans of 134, I too was interested in the envirosafe refrigerant. I bought the 30lb equivalent bottle of it and I am running the stuff in my suburban right now. Seems to work well enough, although my analysis of the results have been nothing more advanced than a hand to the vent. Keeps the car cool enough in Texas heat that my kids cry for me to turn the air off. The high-side pressures aren't as low as they advertise, running around 50psi at 1500rpm, but judging by the noise my compressor is making, that may have very little to do with the refrigerant.

Moral of the story is that the envirosafe works fine. At the time that I bought it, it was cheaper than cans of 134. Shortly after that, I saw that they had 30lb bottles of 134 at our local sams club for something like 130 bucks, so now I have both of those refrigerants sitting in the garage and I do not regret it. I love having a surplus of refrigerants. It's a sickness, I'm sure. If you go for the envirosafe, you will probably need to get the adapter to hook the bottle up to the 134 gauges as the envirosafe bottle has an r-12 size outlet on it.
 

ToddA1

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Haha, no need to weep for me; this is a learning experience with me going the road less traveled. I expected there to be a few glitches, and I was trying to do it as cheaply as possible from the start.

I wish my issue was as simple as improper charge weight, and now that I think about it, I may have caused the early demise of my Denso. There was an instance when the low side shot up to around 85psi when I was charging as a liquid..... I was listening for slugging, never heard it then decided to back off.
Anywho, the lowest I saw a U.S. made cylinder of 134a selling for was $150 shipped. It's still available, so I may still grab one.

My compressor got delivered today. It's not remanufactured as advertised, it's new and it's Chinese. Label on the compressor has the brand as "Omega"; Tough One is only mentioned on the box and there's no mention of 4 Seasons. It has a 2 year warranty (plus 1 year from my credit card company) but hopefully, I'll never need to use it.

Upon opening it, I thought I received a used one. It was greasy, had fingerprints all over it, and the sticker over the ports was half missing. The clutch pulley had no signs of use and the oil I drained looked perfect. I'll hope for the best.








I'm getting too good at this. I had the Denso out, the new compressor in and the car back together in about 1.5 hours. If I didn't have to run out for o-rings, it would have been quicker. The new compressor came with o-rings but they were huge.

Not too much oil came out of the Denso. I'm guessing I lost more oil than I thought when the line blew out of the filter. That may have also helped the compressor go bad.

Anyhow, I pulled vacuum, shut it down and after it held for 20 minutes, I pulled another vacuum for an hour. Hopefully my can tap will arrive tomorrow, and I can recharge with another alternate HC. I'll update later.

-Todd
 

TonyJetta

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Todd,
Was that the compressor from a local auto parts store? It sure looks like it was installed, or someone installed it then pulled it.

Tony
 

ToddA1

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It was ordered from Advance Auto's online site. This was a back ordered part that they ordered from the manufacturer. I waited roughly 2 weeks for them to get in, then it was shipped to me.

-Todd
 

cork

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What about the expansion valve. Have you tried a different one? I don't recall this part as being one that was replaced or changed out throughout this thread. Isn't the expansion valve the culprit in many A/C issues in these cars?
 

ToddA1

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What about the expansion valve. Have you tried a different one?
ToddA1 said:
In a nut shell, I've replaced the drier twice, the TXV three times, replaced the suction reed valve and control valve, flushed 2 times, added a high side filter, replaced the service valves, replaced the compressor with new, and evacuated and recharged many times.

I called Advance Online and they told me to return it to my local store. I called a local store and none of their warehouses in the district show it as available. The manager told me to finish the install and if it didn't work, he'd replace all of the consumables.

Worst case scenario would be me ordering another. I'm hoping for the best case scenario.

-Todd
 

KLXD

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When you drained it did you get the full amount of oil out, or nearly? If so it prolly wasn't run even if installed. Some guy maybe tried to install and it was the wrong one.

At least it has a name on it. My CRAP pump didn't, had a nice generic label.
 

ToddA1

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Something in/on the box said it was prefilled with 5oz of oil. My measuring cup markings are all washed off, but it did look like at least 4 oz.

I use the cup when I'm not concerned about precise measurements. I've been using a graduated brake syringe when I need precise amounts.

-Todd
 
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