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    Thread: A/C question

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      10-02-2012 10:35 AM #1
      The A/C in my 2.0 2000 jetta was the coldest car I ever owned I used to get 37 to 38 degree vent temps but My A/C went warm on me about a month ago one day. I took it to one place and they replaced the Expansion Valve which did not fix the problem, I was upset that they misdiagnosed it so I went to another place, they said the compressor was bad and replaced the Compressor with a aftermarket Sigma JP Compressor and replaced the Accumulator checked for leaks, flushed and re-charged the system. It is blowing cold but the coldest temps I get now is about 45 or 46 range on recirculate.

      My question is can one compressor be colder than another and could it be that the amount of freon is off a little. I would love to get it back to as cold as it used to be. I took it back to the place that replaced the compressor and they said it is all working to specs. Any opinion would be great

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      10-02-2012 10:58 AM #2
      How low does it drop when held in park at 2000-2400 RPM, recirc on?

      What are your working pressures and ambient temp? Ambient temp before it went warm initially?
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      10-02-2012 11:19 AM #3
      Pressure's they listed on the invoice after they fixed it are HI=120-Lo =30. I don't have Ambient temp before just know the vent temp was 38 before and now the best I get is 47 or so.

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      10-02-2012 01:00 PM #4
      Ambient temp is key. What is it right now, with 47* vent temps?
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      10-02-2012 01:35 PM #5
      Quote Originally Posted by ric7744 View Post
      Pressure's they listed on the invoice after they fixed it are HI=120-Lo =30. I don't have Ambient temp before just know the vent temp was 38 before and now the best I get is 47 or so.
      That high of 120 is low, the ambient must be really low to get that.
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      10-02-2012 05:37 PM #6
      Quote Originally Posted by ps2375 View Post
      That high of 120 is low, the ambient must be really low to get that.
      It is a bit low, yes. But I'm skeptical about 37* unless very low ambient temps regardless. On a hot summer day, 47* is fine.
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      10-02-2012 08:25 PM #7
      What do you mean the 120 is low? I am getting 47 degree vent temp even on a mid 70's mild day, where pre part replacement i would have been 38 degree's. What is ambient temp I am a little confused by that. Sorry I don't know a/c at all.

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      10-02-2012 10:42 PM #8
      AC system high side pressure is more dependent upon ambient temp, as it will vary due to that. And the spec for it varies due to what ambient temp is. Without looking in a manual, I can't tell you what it should be, but 120# seems kinda low to me. But, if the system is working, then take it.

      And I really hope you are getting a 30* drop with your AC. But, you really need to run the AC when it is only in the 70's?
      Last edited by ps2375; 10-02-2012 at 10:46 PM.
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      10-02-2012 10:46 PM #9
      That is the thing it is not working as good as I think it should with the new parts. what would be the cause of lower pressure than it should be?

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      10-02-2012 10:54 PM #10
      A low freon charge. And by "freon" I do mean R-134a. I am used to seeing closer to 200#'s, but those are on hotter days and the low side is still in the 30-45# range. I didn't very often measure the temp at the vents, I just looked for it to be cold enough. (as you can tell, I am not a paid AC service tech, just do my own, and topped some off when I was working in a small shop.)
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      10-02-2012 11:20 PM #11
      Maybe that is the issue why it is n't as cold as it was before the compressor went out, they might have not put in enough freon, You think they would put enough being that they are a a/c shop. How do they measure the amount they put in?

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      10-02-2012 11:25 PM #12
      The only real way is to fill an empty system with the desired amount. I don't remember if it is by weight or volume.
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      10-02-2012 11:36 PM #13
      I just did some research on pressures and 120 does seem a little low. why did they turn it back to me that low. It was 80 out the day the did the work.

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      10-03-2012 12:28 AM #14
      Quote Originally Posted by ric7744 View Post
      I just did some research on pressures and 120 does seem a little low. why did they turn it back to me that low. It was 80 out the day the did the work.
      You'll have to ask them that.
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      10-03-2012 09:11 AM #15
      Ambient temp = temp outside.

      A 30* or so drop is fine for an A/C system. For example, mid-70s ambient temp, with mid-40s coming out the vents, I wouldn't think twice about that being a properly operating system.

      Go back and see if they'll evacuate and recharge it again, with the proper amount. It's possible they put in a little less than they should have.
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      10-03-2012 06:24 PM #16
      I don't know about MKIVs, but on MKIIIs, replacing the right part is often a guessing game with the shop getting it wrong before they get it right. If they guessed the expansion valve, and replacing it did not fix the ac, they should not charge you a 2nd time for discharging and recharging the ac system (when they went back in to replace the compressor). The 2nd attempt should only have cost you for the new ac compressor, the accumulator and the labor to R&R the compressor.

      Both the low and high side readings seen too low to me. I'd like to see at least 42-45psi (no more than 48psi) on the low side with the compressor engaged.

      The shop also might not have evacuated the system completely. Leaving air and moisture in the system by incomplete evacuation can lead to inadequate cooling, corrosion in the system, and icing of the evaporator.

      I'd bet that the refrigerant is still low. If you charge/install the weight of refrigerant stated on the ac label under the hood, the ac system refrigerant pressures will be low. To fill to the correct or maximum refrigerant levels takes at least another 1/2 to 3/4 of a can. (12-14oz can).

      Get your own ac manifold gauge set, and verify the pressure readings on the low and high sides of the ac system yourself.
      Last edited by germancarnut51; 10-03-2012 at 06:36 PM.

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      10-04-2012 09:19 AM #17
      Quote Originally Posted by germancarnut51 View Post
      Get your own ac manifold gauge set, and verify the pressure readings on the low and high sides of the ac system yourself.
      He has a point. We're assuming that the tech wrote accurate numbers on the sheet, and we all know what happens when you assume. Verify them.
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      10-10-2012 01:29 AM #18
      So I have a update, took the car back to the A/C shop that fixed it they did a full diagnostic again at no charge, they came to the conclusion that the pressures are all over the place and that the Condensor is plugged up and needs to be replaced and this is the reason the system is not getting as cold as it should be, they said while they were tesing the system they noticed the Radiator had a couple small leaks and should be replaced at the same time. I picked up the car and told them I would think about it. What do you guys think I should do?

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      10-10-2012 04:24 AM #19
      Quote Originally Posted by ric7744 View Post
      So I have a update, took the car back to the A/C shop that fixed it they did a full diagnostic again at no charge, they came to the conclusion that the pressures are all over the place and that the Condensor is plugged up and needs to be replaced and this is the reason the system is not getting as cold as it should be, they said while they were tesing the system they noticed the Radiator had a couple small leaks and should be replaced at the same time. I picked up the car and told them I would think about it. What do you guys think I should do?


      Sounds to me like the ac shop is either incompetent, or knowingly blowing smoke up your rear.

      And now they noticed that the radiator has some small leaks? Sounds to me like theya re trying to deflect, or just keep running up your labor bill. So, course it's possible that the radiator is leaking, how old is it? Did you know you can buy a new OEM radiator for less than $100, and install it yourself in less than two hours?

      How can the pressures be all over the place? How is it that they're just noticing that the condensor has a problem now? What is this, the third time in? Defective compressor? Slipping belt? Bad ac clutch? Blowing smoke to cover lack of knowledge?

      Get your own ac manifold gauge set, and take some measurements. Wait a week and check again to see if the refrigerant pressure is going down to confirm or eliminate the idea that there are leaks.
      Last edited by germancarnut51; 10-10-2012 at 04:28 AM.

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      10-10-2012 10:06 AM #20
      This is only the second time to this shop, the first visit was the place that replaced the exapansion valve and returned the car to me still blowing warm, they told me yesterday that they are sure it is a plugged condenser. I am really not sure either.

      I am sure the Radiator is leaking some it has never been replaced but I am not losing that much coolant at all. Do you have to take out the Condenser to replace the Radiator, they made it sound like you had to. They seem like they are nice and they have good reviews on the net but what symptoms would a clogge Condeser cause?

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      10-10-2012 10:55 AM #21
      Get exact pressure readings to continue. I've never seen a gauge that says "good", "bad", or "all over the place" anywhere on its face.

      Radiator leaks are easy enough to verify, get under there with a flashlight and look. Crusty coolant residue where the side tanks meet the cores would constitute a small leak, and you wouldn't notice much loss.

      I'm still skeptical about there actually being a problem here.

      Oh, and ignore GermanCarNut's tendency to blame the shop so quickly, he automatically assumes that everyone who turns a wrench for a living is a thief and/or con artist.
      Last edited by Anony00GT; 10-10-2012 at 10:58 AM.
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      10-10-2012 01:06 PM #22
      On a MKIII, the condensor attached to the front of the radiator by way of mounting lugs that are molded into the front of the plastic side tanks that are part of the radiator.

      I can't tell you if the same procedure is used to gain access to the radiator and condensor on a MKIV. Your best bet is to buy a Bentley VW Factory Service Manual for MKIVs and read about the instructions for removing the radiator.

      The easiest way to remove the radiator (and not lose the refrigerant charge in the ac system) is to remove the front of the car (bumper, bumper rebar, grille, radiator core support, headlight wiring harness, and headlights) all in one-piece at the same time. This can be done easily after removing about 15 bolts. On a MKIII this takes less than 30 minutes (with one Helper, the first time, and faster after that).

      After that, the radiator and ac condensor are sitting out in the breeeze, and it's easy to remove the four retaining bolt, the hoses, and sensor wires from the radiator, and slip it out to the rear (towards the engine) without discharging the ac system and removing the hoses attached to the condensor.
      Last edited by germancarnut51; 10-10-2012 at 01:10 PM.

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      10-10-2012 01:27 PM #23
      Quote Originally Posted by Anony00GT View Post
      Get exact pressure readings to continue. I've never seen a gauge that says "good", "bad", or "all over the place" anywhere on its face.

      Radiator leaks are easy enough to verify, get under there with a flashlight and look. Crusty coolant residue where the side tanks meet the cores would constitute a small leak, and you wouldn't notice much loss.

      I'm still skeptical about there actually being a problem here.

      Oh, and ignore GermanCarNut's tendency to blame the shop so quickly, he automatically assumes that everyone who turns a wrench for a living is a thief and/or con artist.

      This is why I like to fix mechanical problems. Either the problem was fixed or changed by changing a/some suspect parts, or it was not. The car should not have left the shop without the problem being solved properly.

      What is happening to the OP is exactly why I learned to fix my car myself a ling time ago. Whether the mechanics at the two shops he's been two are sloppy or incompetent doesn't make any difference to me, because the car should not left the ship either time without being cured, and the Owner should not have paid twice (going on three times) it get the issue resolved. The OP should have taken the car back to the first shop, and not have taken the car to the second shop, and paid a second time to get his ac fixed. That mistake is on him.

      But both shops errored by not fixing the problem before the OP left the shop each time.

      Now he's paid twice, and still doesn't have a fully functional ac system. I doubt that the condensor is plugged and causing the pressure to flucuate in either or both sides of the ac system. To my way of thinking, now he has a problem with the way the system was evacuated after the compressor was replaced, or a low refrigerant problem, or a bad replacement compressor.

      The compressor may not have even been bad in the first place, it may have been low refrigerant level all along. But, there's no way to tell for sure, without pressure readings from the first shop or the second shop after the expansion valve was replaced, and before the compressor was replaced.
      Last edited by germancarnut51; 10-10-2012 at 01:31 PM.

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      10-10-2012 03:15 PM #24
      Quote Originally Posted by germancarnut51 View Post
      Now he's paid twice, and still doesn't have a fully functional ac system.
      Without live pressure readings, I can't agree with that. An A/C system blowing 30* below ambient is functioning.
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      10-15-2012 10:23 AM #25
      what would be a fair price to get the Condensor changed? I still have not done anything more about the system, maybe I should wait until after the winter now that it is cooling down.

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      10-15-2012 12:21 PM #26
      Quote Originally Posted by ric7744 View Post
      what would be a fair price to get the Condensor changed? I still have not done anything more about the system, maybe I should wait until after the winter now that it is cooling down.
      Condenser lists for $300
      Book time - 2.1 hours (going rate around here is ~$90/hr) = $189
      Evacuate and Recharge, assuming you need no additional refrigerant, about $50

      So, $300 + 189 + 50 = $539.00 That's a fair price before tax and shop fees. If you use the same shop, you can probably get them to take off the fee for evac & recharge, that wouldn't be an unreasonable request given your situation.

      I'd definitely want to see pressures before definitively calling a clogged condenser though.
      Last edited by Anony00GT; 10-15-2012 at 12:23 PM.
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      10-21-2012 03:19 PM #27
      So update it has been back at shop since wednesday. They still can't figure out what is wrong. They put a condenser in and it is still not working properly. They are not going to charge me for anything yet. They said they can't figure out what is wrong and it much be something out of the ordinary. He said don't worry about any money charge right now they becuase there is no charge they just want to locate the problem. He said they do nothing but a/c and rarely have a car where they just can't pinpoint the problem. What do you guys think?

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      10-22-2012 04:57 PM #28
      Interesting. I'd like to know what they come up with.

      At least they're doing right by you and not charging you for repairs that aren't going to fix the problem.
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      10-22-2012 05:58 PM #29
      Maybe the evaporator is choked with dirt. A dirty evaporator would keep the ac from transfering the cold to the incoming fresh air efficiently.

      I've never tried to do it, but is there a way to inspect the exterior condition of the evaporator without tearing down the entire ventilation system?

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      10-22-2012 10:07 PM #30
      Remove blower motor and look.
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      10-26-2012 10:38 AM #31
      So I have the car back they flushed the system again and said the pressures and system seem to be working well they did put in a new Condensor and only charged me $200, I really can't test out how cold it is because it has been really cold here in Northern California. We might get up to the mid 70's today so I will test it out.
      Last edited by ric7744; 10-28-2012 at 01:49 PM.

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      10-27-2012 06:07 PM #32
      so tested the car out today 80 degrees out and my digital guage was measuring between 37 and 43 degrees. it was going colder and then warmer in a consistant cycle. I looked under the hood and the two big blower fans in front of the engine cycle on and of stays on for about 7 seconds and then turns off. I don't remember those fans cycling like that before is that normal? The compressor seems to be on all the time but those two fans cycle constantly.

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      10-27-2012 10:47 PM #33
      Quote Originally Posted by ric7744 View Post
      so tested the car out today 80 degrees out and my digital guage was measuring between 37 and 43 degrees. it was going colder and then warmer in a consistant cycle. I looked under the hood and the two big blower fans in front of the engine cycle on and of stays on for about 7 seconds and then turns off. I don't remember those fans cycling like that before is that normal? The compressor seems to be on all the time but those two fans cycle constantly.

      That could be your answer right there.

      I've never seen a car that cycled the cooling fans on and off while the ac was engaged. The cooling fans on every car I've ever owned or worked on run on high when the ac is running. That would definitely affect the temperature of the conditioned air, as the temperature of the refrigerant is definitely going to make a difference.

      But on the other hand, the newest car I have is the 97 Jetta. Maybe newer cars cycle the cooling fan now. Or, maybe there's something wrong with the cooling fan circuitry, or the ac circuitry related to running the cooling fan when the ac is switched on.

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      10-28-2012 03:22 AM #34
      The air is blowing cold now but is it normal for the cooling fans to cycle like that? they never stop spinning but they go about 7 seconds on and then cut out and the slow down and then they turn back on and you can see the temp vary with when they turn on and off.

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      10-28-2012 01:34 PM #35
      Is it normal for the cooling fans to cycle on and off all the time. they don't stop spinning but they engage on and off about every 7 seconds.

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