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  1. #1
    Veteran Member Four Rings MarcusDubya77's Avatar
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    Question Really need help resolving/isolating an issue

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    I have searched, but everything that I have found is all over the place and really not helpful thus far...

    I will sort of lay this all out. A couple of months ago I replaced the pressure switch for my A/C. We had a real issue with the A/C that wasn't noticeable until we were moving in the dead of summer. I had, also, accid3entaly overcharged our A/C which has since been depressurized to normal. However, I think there is some other underlying issue that is causing this. I will sort of do my best to explain it...

    1. The coolant light has been sporadically coming on and off. However, the temperatures have remained "normal". Oil at ~202-220 when fully warmed up and coolant at (according to the P3 gauge) ~200-220. The temperature outside has been anywhere from about 70 in the morning to about 90 in the afternoon. Oil and coolant temperatures fall in line with these thresholds of the temp outside.

    2. The A/C is turned all the way to low and in recirc mode. The morning seems to be ok, however the afternoon is not too Bueno. The A/C will only blow warm air when moving, and sporadically cool when stopped or when I have attempted to cycle A/C off and on.

    3. The aux fan is working (I think), however, it was not running when I parked the car in the hot afternoon after coming home from work.

    Things I have already tried:
    1. Replaced pressure switch
    2. recharge and Discharge A/C
    3. Filled coolant.
    4. Checked fuses

    Other things that I think I should check/replace:
    1. Fan relay (still need to know which ones)
    2. Coolant expansion tank sensor
    3. Water pump

    So...
    1. Do these sound like issues that could be somehow related?
    2. Is there a certain order in which I should check these items?
    3. Is there anything I am missing here?
    4. How can I use VAGCOM to hopefully further isolate the issue?

    Any help would be greatly appreciated.
    Last edited by MarcusDubya77; 06-29-2017 at 05:37 AM. Reason: Better described.
    07 Phantom Black JHM-SC

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  2. #2
    Veteran Member Four Rings MarcusDubya77's Avatar
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    Anybody?

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  3. #3
    Veteran Member Three Rings
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    Quote Originally Posted by MarcusDubya77 View Post
    I have searched, but everything that I have found is all over the place and really not helpful thus far...

    I will sort of lay this all out. A couple of months ago I replaced the pressure switch for my A/C. We had a real issue with the A/C that wasn't noticeable until we were moving in the dead of summer. I had, also, accid3entaly overcharged our A/C which has since been depressurized to normal. However, I think there is some other underlying issue that is causing this. I will sort of do my best to explain it...

    1. The coolant light has been sporadically coming on and off. However, the temperatures have remained "normal". Oil at ~202-220 when fully warmed up and coolant at (according to the P3 gauge) ~200-220. The temperature outside has been anywhere from about 70 in the morning to about 90 in the afternoon. Oil and coolant temperatures fall in line with these thresholds of the temp outside.

    2. The A/C is turned all the way to low and in recirc mode. The morning seems to be ok, however the afternoon is not too Bueno. The A/C will only blow warm air when moving, and sporadically cool when stopped or when I have attempted to cycle A/C off and on.

    3. The aux fan is working (I think), however, it was not running when I parked the car in the hot afternoon after coming home from work.

    Things I have already tried:
    1. Replaced pressure switch
    2. recharge and Discharge A/C
    3. Filled coolant.
    4. Checked fuses

    Other things that I think I should check/replace:
    1. Fan relay (still need to know which ones)
    2. Coolant expansion tank sensor
    3. Water pump

    So...
    1. Do these sound like issues that could be somehow related?
    2. Is there a certain order in which I should check these items?
    3. Is there anything I am missing here?
    4. How can I use VAGCOM to hopefully further isolate the issue?

    Any help would be greatly appreciated.
    So your having issues with your A/C. What are your pressures when you hook up the A/C machine. Need to get both high side and low side pressures.

  4. #4
    Established Member Two Rings 978rs4's Avatar
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    So long story short your ac will blow warm and then cool. You could have many thins going on. But most likely is a small leak. You need to recover the ac charge and see if it still has the same amount of refrigerant according to the vehicle spec. And also check for faults in whole vehicle. After you confirm this data then you can continue with diagnosis


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  5. #5
    Veteran Member Four Rings MarcusDubya77's Avatar
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    So, pressure tested and no leaks. They have refilled Freon, but still is warm. I ran output tests in the J293 module and the fan ran when power was applied. However, ran the HVAC output test and the coolant fans did not run. Maybe bad J293 module?? Thoughts?

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  6. #6
    Veteran Member Four Rings MarcusDubya77's Avatar
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  7. #7
    Veteran Member Four Rings MarcusDubya77's Avatar
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    I replaced the expansion tank, and it has alleviated the coolant light, but this A/C issue is killing me. I would definitely appreciate anybody with some insight on this issue.
    07 Phantom Black JHM-SC

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  8. #8
    Veteran Member Three Rings
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    When you say A/C is not cold while you're moving makes me feel like it isn't a fan issue. Usually, the fan is there for when you're not moving and pressure inside the A/C system builds up due to lack of air flow and heat from sitting idle.

    Also if possible can you get the pressure readings from low and high side while at idle. If you don't own gauges maybe ask the shop your getting it serviced at. Normally you'll want pressures in the 30's for low and 250 - 280 for high. If the high side higher than that and the fan isnt on then it's probably a fan issue.
    Last edited by Kambesama; 07-17-2017 at 12:56 PM.

  9. #9
    Veteran Member Four Rings MarcusDubya77's Avatar
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    I spoke to them, and unfortunately they didn't keep any of the readings. I do have VAGCOM and could see if there is anything that it sees. I only think that the fan controller or relay might be in play since output tests to the HVAC didn't kick the fans on, but output test through the instrumentation part of VAGCOM testing did turn them on.
    07 Phantom Black JHM-SC

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  10. #10
    Veteran Member Four Rings badbluers4's Avatar
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    Probably a bad compressor.

  11. #11
    Veteran Member Four Rings MarcusDubya77's Avatar
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    That's a pretty grim prediction. Is there a real good way to test it? Any real noticeable "Eurekas!" that would confirm this?
    07 Phantom Black JHM-SC

    "Bitches... Come over here and have sex with Charlie Murphy" ~ Rick James

  12. #12
    I don't think that there is an issue with the fans. Try going into 01 or 11 engine electronics and run the output test to see if the fans come on.

    For the AC problem. Please go into the 08-HVAC module and look at measuring value blocks 1, 10, and 11 at idle with the AC off, then on, and then check while driving with the AC off and then on.

    Channel 1 should show: AC valve (N280) Current, AC valve (280) duty cycle, high pressure signal (G65), and Refrigerant circuit pressure.
    Channel 10 should show temperatures II: Evaporator outflow temp, fresh air intake duct temp, calculated ambient air temp, and measured ambient air temp.
    Channel 11 should show temperatures III: dash panel temp, temp sensor blower speed, coolant temp, and idle speed increase request.

    I am trying to see if the compressor is actually working. If it has no duty cycle when the AC is on then something electrical is probably causing a problem to not let the compressor come on since you said that the refrigerant is at the correct amount. By the way with the JHM SC, they say in the instructions for the S4s to fill to 530-540 grams because of the additional length of the lines, not sure about the RS4s. Then if the duty cycle does go up to like 60-75% but the refrigerant circuit pressure doesn't raise from like 4-5 bar to 15-17 bar then the compressor physically isn't building high enough high side pressure. The temperature readings are there as another way to confirm that the compressor is working and if the evaporator is actually getting cold compared to ambient.

    The RS4s use the same garbage AC compressor as the B6/7 S4s and basically all the MPI 4.2 timing chain engines, the 4.2 FSI V8s, and the 5.2 FSI V10s. Some of the part numbers are different if you were to actually look it up but the Nissens AC compressor claims to fit all of those engines.

  13. #13
    Veteran Member Four Rings MarcusDubya77's Avatar
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    Thanks. I will run those tests when I get home today. More to follow.
    07 Phantom Black JHM-SC

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  14. #14
    Veteran Member Four Rings MarcusDubya77's Avatar
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    These are off and on at idle. I will have to wait to drive. At idle it blows ice cold. Driving is when it starts to go through the weird warm and cool cycle.

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  15. #15
    Established Member Two Rings 978rs4's Avatar
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    You really need a set of gauges on it to see what's happening when it goes warm. Did the shop recover the charge? And was it at the vehicles spec? Because if it has a low charge like only 300-250 grams your AC will go cold at then hot. You also will not have any codes. Also did anyone add sealer from one of those stupid autozone cans because that can fuck the whole system up


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  16. #16
    Those readings at idle are pretty good so I really need to see what the readings are while moving, especially when it is acting up if possible. Strongly recommend that you have someone else watch the laptop and take pictures of the readings while you are driving to avoid being distracted while driving - just have to say that because some people don't think about it. My S4 was very similar but I think that it was hotter out when I checked mine because the temperature readings were higher.

  17. #17
    Veteran Member Four Rings MarcusDubya77's Avatar
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    Quote Originally Posted by JimmyBones View Post
    Those readings at idle are pretty good so I really need to see what the readings are while moving, especially when it is acting up if possible. Strongly recommend that you have someone else watch the laptop and take pictures of the readings while you are driving to avoid being distracted while driving - just have to say that because some people don't think about it. My S4 was very similar but I think that it was hotter out when I checked mine because the temperature readings were higher.
    I will definitely be doing that. Right now it is taped up, so I can wax and detail. Luckily, I have my hippy Prius daily. I should be able to get some readings later this week.
    07 Phantom Black JHM-SC

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  18. #18
    Veteran Member Four Rings MarcusDubya77's Avatar
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    Quote Originally Posted by 978rs4 View Post
    You really need a set of gauges on it to see what's happening when it goes warm. Did the shop recover the charge? And was it at the vehicles spec? Because if it has a low charge like only 300-250 grams your AC will go cold at then hot. You also will not have any codes. Also did anyone add sealer from one of those stupid autozone cans because that can fuck the whole system up


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    The shop did, and added about 2lbs Freon (I am guessing the extra comes from the S/C lines. The guys at Goodyear said its holding pressure, and added some UV dye in case I have to bring it back. I had added some 134 but no sealer. Had no real choice, as my family and I were moving from CO to AL and had no real time to do any A/C servicing. The temp in KS was 105, and black on black doesn't help....
    07 Phantom Black JHM-SC

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  19. #19
    Established Member Two Rings 978rs4's Avatar
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    Well if you look under the hood there should be a spec on how many grams of r134a it takes without looking at mine it's about 450g or close to that 2 lbs would be around 900grams and the system will be overcharged and will not work correctly


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  20. #20
    Veteran Member Four Rings MarcusDubya77's Avatar
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    Quote Originally Posted by 978rs4 View Post
    Well if you look under the hood there should be a spec on how many grams of r134a it takes without looking at mine it's about 450g or close to that 2 lbs would be around 900grams and the system will be overcharged and will not work correctly


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    Just realized that I misquoted the amount. The service included up to 2lbs of Freon. Rechecked and the tech said 1lb. Stated the machine detects when full.
    07 Phantom Black JHM-SC

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  21. #21
    Veteran Member Four Rings koolade9's Avatar
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    Nowhere have you mentioned replacing the orifice tube...

    Vac it down properly, and use actual 134a (none of the 'stop-leak' / 'leak detection', no additives, no autozone BS). Gauges should be used to monitor operation during charging, but don't let pressures dictate the amount of refrigerant you use. Charge with exact amount (I don't recall, but check the manual, search, or look under the hood). Don't ever ever "top off" your refrigerant.
    FRRG AZ Ring

  22. #22
    Veteran Member Four Rings MarcusDubya77's Avatar
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    This is the first that I took notice to that. I guess I need look up ways to check it. The other stuff has already been done. I had it serviced and tested at Goodyear this last weekend. They tested and at least were able to confirm their were no leaks. It holds pressure. I will definitely look into the orifice tube.
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  23. #23
    Veteran Member Four Rings koolade9's Avatar
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    Quote Originally Posted by MarcusDubya77 View Post
    This is the first that I took notice to that. I guess I need look up ways to check it. The other stuff has already been done. I had it serviced and tested at Goodyear this last weekend. They tested and at least were able to confirm their were no leaks. It holds pressure. I will definitely look into the orifice tube.
    The orifice tube acts like an expansion valve. If you disconnect the lines where they pass through the firewall, you can pull out the orifice tube with a needle-nose. Just replace it, they're cheap last I checked (<$30) and could certainly cause your issue. If it's broken, pray to whatever deity you choose that the trash didn't make it's way to the compressor. It doesn't sound like that's the case though.

    Also, if the system has been open and exposed to ambient air for any prolonged period of time, you should also replace the drier. I'm guessing it's a bit humid in Alabama this time of year, and the desiccant will become useless rather quickly.

    When they "tested", what exactly did they test? Generally, I'll vac down a system with a target of 27-28in hg (will depend on the strength of your vacuum pump), then let that sit overnight. If it holds, I'll vac it down a bit more and re-charge. The machine certainly makes it easier for techs to discharge/charge A/C systems, and it's better for the environment by not dumping refrigerant, but the machine can't simulate time.
    FRRG AZ Ring

  24. #24
    Quote Originally Posted by MarcusDubya77 View Post
    Just realized that I misquoted the amount. The service included up to 2lbs of Freon. Rechecked and the tech said 1lb. Stated the machine detects when full.
    I very quickly checked what a pound converts to Kilograms in Google and it states that 1 pound equals 0.454 Kilograms. That means that the system was charged to around 454 grams (there is a bit of wiggle room for error) when you need probably 530-540 grams. That would be under charged but I wonder if the machine used just is not very exact.

    For context, I finally had to break down and buy a Robinair AC machine on sale because they are used by dealerships so I am familiar with them and are mostly about as accurate as possible. Best $2K or more expensive tool/machine that I have ever purchased. It really doesn't make sense why shops skip on shitty AC machines.

    Did the shop say how much refrigerant came out? I might have missed that if you posted it already.

    Quote Originally Posted by koolade9 View Post
    Nowhere have you mentioned replacing the orifice tube...

    Vac it down properly, and use actual 134a (none of the 'stop-leak' / 'leak detection', no additives, no autozone BS). Gauges should be used to monitor operation during charging, but don't let pressures dictate the amount of refrigerant you use. Charge with exact amount (I don't recall, but check the manual, search, or look under the hood). Don't ever ever "top off" your refrigerant.
    Quote Originally Posted by koolade9 View Post
    The orifice tube acts like an expansion valve. If you disconnect the lines where they pass through the firewall, you can pull out the orifice tube with a needle-nose. Just replace it, they're cheap last I checked (<$30) and could certainly cause your issue. If it's broken, pray to whatever deity you choose that the trash didn't make it's way to the compressor. It doesn't sound like that's the case though.

    Also, if the system has been open and exposed to ambient air for any prolonged period of time, you should also replace the drier. I'm guessing it's a bit humid in Alabama this time of year, and the desiccant will become useless rather quickly.

    When they "tested", what exactly did they test? Generally, I'll vac down a system with a target of 27-28in hg (will depend on the strength of your vacuum pump), then let that sit overnight. If it holds, I'll vac it down a bit more and re-charge. The machine certainly makes it easier for techs to discharge/charge A/C systems, and it's better for the environment by not dumping refrigerant, but the machine can't simulate time.
    A lot of people confuse orifice tubes with expansion valves. The orifice tube that is used in these cars is simply a restrictor to convert the high side portion of the AC system to the low side portion. It is not internally or externally regulated like an expansion valve so the refrigerant flow is regulated by the duty cycle of the compressor. I had to argue these points with a company a little while ago because the AC system wasn't working correctly when trying to modify it. So if the orifice tube was clogged with crap then the AC probably wouldn't work at all.

    I agree with the points of the drier but we would need to know if the AC system was open for a while or had a leak.

    There is no way that a shop would let a car sit overnight to see if the vacuum on the AC system holds. Way too much time and money lost from wasting time. It would be a better idea to add die, recharge the system, and let the customer drive the car around for a bit. My machine defaults to 10 minutes to pull vacuum on the system and I usually let it sit for a few minutes after to see if it leaks down. Then recharge and hope for the best.

  25. #25
    Veteran Member Four Rings MarcusDubya77's Avatar
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    I think I am actually going to have them recheck the system and record numbers on high and low. The inspection they did was very minimal and part of a "manager's special" for $9.95. I was just trying to see if they could actually find a leak and hopefully charge up any that was lost. SO, I will probably do a complete evacuation and recharge of the entire system along with checking for leaks in the dye. First, I will do a run to check 1,10, and 11 whilst driving the car. Luckily, I am amassing quite a collection of HVAC related components in the event of future faults...It doesn't help that its 90+ with 60-80% humidity down here, and a black/black car is roasting in a parking lot all day with little shade (when I take it to work)....
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  26. #26
    Veteran Member Four Rings koolade9's Avatar
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    Quote Originally Posted by JimmyBones View Post
    A lot of people confuse orifice tubes with expansion valves. The orifice tube that is used in these cars is simply a restrictor to convert the high side portion of the AC system to the low side portion. It is not internally or externally regulated like an expansion valve so the refrigerant flow is regulated by the duty cycle of the compressor. I had to argue these points with a company a little while ago because the AC system wasn't working correctly when trying to modify it. So if the orifice tube was clogged with crap then the AC probably wouldn't work at all.

    I agree with the points of the drier but we would need to know if the AC system was open for a while or had a leak.

    There is no way that a shop would let a car sit overnight to see if the vacuum on the AC system holds. Way too much time and money lost from wasting time. It would be a better idea to add die, recharge the system, and let the customer drive the car around for a bit. My machine defaults to 10 minutes to pull vacuum on the system and I usually let it sit for a few minutes after to see if it leaks down. Then recharge and hope for the best.
    I agree with all the above, a clogged orifice tube is what I'm pointing to as a potential cause. What you find in the orifice tube could also be an indicator of what else may be happening in the system. And I get it, shops aren't going to put that kind of time in it for such a small service. I'm just calling out the process for those who feel comfortable taking a stab at it on their own. Living in the desert, I was forced to learn.
    FRRG AZ Ring

  27. #27
    Quote Originally Posted by MarcusDubya77 View Post
    I think I am actually going to have them recheck the system and record numbers on high and low. The inspection they did was very minimal and part of a "manager's special" for $9.95. I was just trying to see if they could actually find a leak and hopefully charge up any that was lost. SO, I will probably do a complete evacuation and recharge of the entire system along with checking for leaks in the dye. First, I will do a run to check 1,10, and 11 whilst driving the car. Luckily, I am amassing quite a collection of HVAC related components in the event of future faults...It doesn't help that its 90+ with 60-80% humidity down here, and a black/black car is roasting in a parking lot all day with little shade (when I take it to work)....
    Sounds like a plan.

    Don't worry it sucks when you have a green car with tan interior with no AC in similar conditions. The AC compressor died on my A6 and it has been mid 90s with 80 or higher percent humidity in the DC area. Can't complain too much since it has been a good solder for 18 years and just over 316,800 miles.

    Quote Originally Posted by koolade9 View Post
    I agree with all the above, a clogged orifice tube is what I'm pointing to as a potential cause. What you find in the orifice tube could also be an indicator of what else may be happening in the system. And I get it, shops aren't going to put that kind of time in it for such a small service. I'm just calling out the process for those who feel comfortable taking a stab at it on their own. Living in the desert, I was forced to learn.
    I agree that it would be helpful to pull the orifice tube to see if there is any obvious signs of a problem but that requires removing the refrigerant first.

  28. #28
    Established Member Two Rings KunzeRob's Avatar
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    Just out of curiosity: what's the minimum Evaporator Outflow Temp (G263) to be expected for a perfectly running AC? In my B7 S4 it went down to 1.5C in ~30C Ambient Temp / 34C Fresh Air Intake...

    I remember sitting in 1994 in an old Mercury in hot Tennessee summer and with the AC on it felt extremely cold and even had condensation on the windshield. Couple weeks ago in 115F my AC had real trouble to get convenient temperature in my car...

  29. #29
    Quote Originally Posted by KunzeRob View Post
    Just out of curiosity: what's the minimum Evaporator Outflow Temp (G263) to be expected for a perfectly running AC? In my B7 S4 it went down to 1.5C in ~30C Ambient Temp / 34C Fresh Air Intake...

    I remember sitting in 1994 in an old Mercury in hot Tennessee summer and with the AC on it felt extremely cold and even had condensation on the windshield. Couple weeks ago in 115F my AC had real trouble to get convenient temperature in my car...
    That is a hard question to answer. The evaporator is only going to get so cold compared to ambient and I doubt that people would be willing to test the AC in really cold weather like Canadian winters. There is no low side temperature or pressure sensor so it is possible for the evaporator to freeze over but it would have to be cold as hell ambient temperature wise to begin with.

    Was the old Mercury using R134A or R12 refrigerant? It might have been using R12 which works better for getting the air colder but it has been phased out a long time ago since it is hurtful to the environment. Actually R134A (what is used in these cars) is being phased out too and the newer Audis are catching on fire because of the new refrigerant leaking.

  30. #30
    Veteran Member Four Rings MarcusDubya77's Avatar
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    I am glad you posted that bit about emptying the refrigerant prior to checking orifice tube..My dumb ass would have literally opened a charged system....Your statement gave me an epiphany about remembering the system is charged. Should I have them discharge it, replace the orifice, and recharge??
    07 Phantom Black JHM-SC

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  31. #31
    Veteran Member Four Rings LINDW4LL's Avatar
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    Maybe I missed it, but did you check your HVAC system for fault codes with VAG-COM? I see you were looking at measuring blocks above but I don't see any mention of codes.

    I had a bad inlet air temperature sensor in my B5 S4 causing sporadic warm air.
    -Hayden


  32. #32
    Veteran Member Four Rings MarcusDubya77's Avatar
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    Oh yeah.. Nothing at all.. I am starting to be concerned that I am crazy, and that there might be nothing at all..Maybe our A/C systems just suck butt.
    07 Phantom Black JHM-SC

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  33. #33
    Established Member Two Rings KunzeRob's Avatar
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    Quote Originally Posted by JimmyBones View Post
    The evaporator is only going to get so cold compared to ambient and I doubt that people would be willing to test the AC in really cold weather like Canadian winters.
    I believe below 10C the A/C would not turn on to protect it from damage.

    Quote Originally Posted by JimmyBones View Post
    Was the old Mercury using R134A or R12 refrigerant?
    That's a good point. It might have been R12 or so.

    Thanks!
    Robert

  34. #34
    Quote Originally Posted by MarcusDubya77 View Post
    I am glad you posted that bit about emptying the refrigerant prior to checking orifice tube..My dumb ass would have literally opened a charged system....Your statement gave me an epiphany about remembering the system is charged. Should I have them discharge it, replace the orifice, and recharge??
    I have opened AC systems by accident that still had refrigerant in them and trust me it isn't good for your health. Especially if it gets on you but most of the time it will just mess with your breathing and smell really bad.

    Quote Originally Posted by LINDW4LL View Post
    Maybe I missed it, but did you check your HVAC system for fault codes with VAG-COM? I see you were looking at measuring blocks above but I don't see any mention of codes.

    I had a bad inlet air temperature sensor in my B5 S4 causing sporadic warm air.
    It is rare to get codes for the HVAC system. A B5 A4 that I worked a while ago wouldn't blow cold air at all because the ambient air temperature sensor was defective and it didn't throw codes. I had to look at the measuring value blocks to see that it thought that it was really far in the negative for ambient temperatures. The OP should be able to scroll through the middle instrument cluster screens to see the ambient air temperature readings.

    Quote Originally Posted by MarcusDubya77 View Post
    Oh yeah.. Nothing at all.. I am starting to be concerned that I am crazy, and that there might be nothing at all..Maybe our A/C systems just suck butt.
    Well they do suck in comparison to some systems but when mine works, it works well.

    Quote Originally Posted by KunzeRob View Post
    I believe below 10C the A/C would not turn on to protect it from damage.


    That's a good point. It might have been R12 or so.

    Thanks!
    Robert
    It is possible but I don't remember the threshold off hand.

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