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    Thread: AC blows hot, low side pressure is high

    1. Member Govt-Cheese's Avatar
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      99 Jetta Mk. III VR6 5 spd silver, 2002 Audi TT quattro roadster white
      07-14-2010 08:50 PM #1
      I'm not much of an air conditioning expert, any advice would be appreciated.

      My Jetta's AC was slowly getting warmer and warmer, now it doesn't cool at all. When you hit the AC button the compressor still comes on though, I double checked. I checked it with an AC manifold, it says the low side has 80-90 psi of refridgerant, which is too high. Not sure what's going on.... Any suggestions?

    2. 07-14-2010 09:16 PM #2
      not sure from your description. 80 to 90 psig would be normal if you were checking without the compressor running. i guess it's possible that the compressor has died. test the low side with the compressor off and again with the compressor on. is there any difference in pressure? and you are sure that when the compressor is running that the end plate of the compressor clutch is spinning?

    3. Member Govt-Cheese's Avatar
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      99 Jetta Mk. III VR6 5 spd silver, 2002 Audi TT quattro roadster white
      07-14-2010 09:36 PM #3
      That psi was with the compressor running, I don't remember if I checked it with AC off. Yes we visually confirmed the clutch engaging on the compressor. I'll check the pressure tomorrow again, on and off and see if I get a difference.
      2002 Audi TT Quattro roadster, white, baseball glove seats, 19" aftermarket rims, Pioneer HU with Rockford Fosgate/MB Quart speakers.
      '99 Jetta GLX. Rebuilt AAA VR6 (blown head gasket), Black Forest Stage 2 PEM, Autotech 262 cams, VWVortex's airbox mod with K&N filter, deleted cat and suitcase muffler, Pioneer HU, 17" rims.

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      07-15-2010 04:32 AM #4
      You need to state the high and low side pressures at the same time...

      #1 Pressures with the engine and ac off.

      #2 Pressures with the enging running, and ac switched on with the compressor clutch engaged.

      Just went through this on a friend's sister's 97 Jetta GLS.

      Pressure was about 100psi on both the high and low sides with the engine and ac switched off.

      Pressure was about 100psi on the low side, and 80psi on the high side with the engine and ac switched on and the compressor clutch engaged.

      My guess was that the compressor was bad.

      Slapped in a spare used compressor with a new drier, ran a vacuum for almost an hour. Shut-off the vacuum pump, and watched the vacuum for 30 minutes. Vacuum seal was okay, so we injected a 3oz of PAG oil, and about 30oz of R134a (about (2 1/2) 12oz cans).

      And the result was cold ac.

    5. Member Govt-Cheese's Avatar
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      99 Jetta Mk. III VR6 5 spd silver, 2002 Audi TT quattro roadster white
      07-19-2010 04:27 PM #5
      Sorry for the slow reply, just had a chance to check this.

      With the AC off, high press side is about 120, low press is too high, off the dial

      With the AC on, compressor spinning, high side is 150, low side is 85-90.

      Sounds like maybe bad compressor?
      2002 Audi TT Quattro roadster, white, baseball glove seats, 19" aftermarket rims, Pioneer HU with Rockford Fosgate/MB Quart speakers.
      '99 Jetta GLX. Rebuilt AAA VR6 (blown head gasket), Black Forest Stage 2 PEM, Autotech 262 cams, VWVortex's airbox mod with K&N filter, deleted cat and suitcase muffler, Pioneer HU, 17" rims.

    6. Senior Member reynolds9000's Avatar
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      07-19-2010 05:35 PM #6
      subscribed because i had the exact same issue. high side pressue is around 120 consistantly. i tried adding r134a and it wouldn't suck any into the system. my a/c blows how but the compressor kicks on when you hit the a/c button.

    7. 07-19-2010 06:40 PM #7
      sounds like you are not moving any refrigerant which could be a bad compressor or a plugged expansion valve. i'm leaning toward the compressor.

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      07-19-2010 07:33 PM #8
      Quote Originally Posted by reynolds9000 View Post
      subscribed because i had the exact same issue. high side pressue is around 120 consistantly. i tried adding r134a and it wouldn't suck any into the system. my a/c blows how but the compressor kicks on when you hit the a/c button.
      You need to quote the low and high side pressures both with the ac off, and with the ac on, engine running, and the ac clutch engaged (compressor turning).

    9. Member Govt-Cheese's Avatar
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      07-19-2010 08:43 PM #9
      Should I try expansion valve first? Compressors run $250 and up, expansion valve is $50 at Advance.....
      2002 Audi TT Quattro roadster, white, baseball glove seats, 19" aftermarket rims, Pioneer HU with Rockford Fosgate/MB Quart speakers.
      '99 Jetta GLX. Rebuilt AAA VR6 (blown head gasket), Black Forest Stage 2 PEM, Autotech 262 cams, VWVortex's airbox mod with K&N filter, deleted cat and suitcase muffler, Pioneer HU, 17" rims.

    10. 07-19-2010 11:26 PM #10
      the problem with that is, either of those requires removing the refrigerant from the system, and then pulling a vacuum and recharging when you are done. if you misguess the first time, you have to do it all over again. you haven't by chance lost all the refrigerant from a leak or something and just added refrigerant without pulling a vacuum first have you? the symptoms also match air instead of refrigerant in the system.

    11. Member Govt-Cheese's Avatar
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      99 Jetta Mk. III VR6 5 spd silver, 2002 Audi TT quattro roadster white
      07-20-2010 05:53 PM #11
      I haven't added any r134 or really touched the AC system since I bought the car and restored it to running condition this winter. The AC worked good until just recently. I know about removing all the refridgerant and creating a vacuum before filling after opening the system as well. If there's air in the system, it's from a leak Maybe I should vacuum it then check how long the vacuum stays? Or at least see if it stays for an hr or two....
      2002 Audi TT Quattro roadster, white, baseball glove seats, 19" aftermarket rims, Pioneer HU with Rockford Fosgate/MB Quart speakers.
      '99 Jetta GLX. Rebuilt AAA VR6 (blown head gasket), Black Forest Stage 2 PEM, Autotech 262 cams, VWVortex's airbox mod with K&N filter, deleted cat and suitcase muffler, Pioneer HU, 17" rims.

    12. n00b
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      07-20-2010 10:40 PM #12
      I am having a similar problem with my Golf. I have not worked with AC before though. How much work is required to drain the system and pull vacuum?

    13. Member Govt-Cheese's Avatar
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      07-20-2010 10:59 PM #13
      You need to have a vacuum pump (I rented from Autozone, $200 but they refund whole amount when I return) and pressure manifold gauges ($40 in the offseason, $80 now!). You have to vacuum the system out completely, there can be no regular air pressure inthe system when you're done or the compressor will not engage. You can top it off or drain and refill with the manifold.
      2002 Audi TT Quattro roadster, white, baseball glove seats, 19" aftermarket rims, Pioneer HU with Rockford Fosgate/MB Quart speakers.
      '99 Jetta GLX. Rebuilt AAA VR6 (blown head gasket), Black Forest Stage 2 PEM, Autotech 262 cams, VWVortex's airbox mod with K&N filter, deleted cat and suitcase muffler, Pioneer HU, 17" rims.

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      07-21-2010 01:50 AM #14
      You need to have your own ac manifold gauge set if you're going to be filling and diagnosing ac systems.

      Harbor Freight usually has theirs on sale. The deal right now is $45, and you can get a 20% Off Coupon from a HF ad in the Sunday newspaper, or from the back of many different magazines.

      If the ac system loses all of it's refrigerant charge, or is opened for service/parts replacement, you will need to draw a vacuum to remove the air, and boil off all the moisture that's accumulated in the system. You can get an air compressor powered vacuum pump for about $10 from HF, or an ac powered vacuum pump for $80 less 20% for the coupon.

      I've used a HF air compressor powered vacuum pump with great results for the past 10 years. But, I thinking about getting the ac powered compressor to save on electricity. You end up running the vacuum pump for a minimum of an hour at a time, and my 5.5hp air compressor sucks alot of electricity compared to a little 2.5cfm vacuum pump.

    15. Member Govt-Cheese's Avatar
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      03-06-2011 03:48 PM #15
      I didn't drive my car much after this conversation originally happened due to coil pack issues but I'm back on the road now and Florida is already heating up. I'm going to order an AC compressor with clutch and replace that. What do you think of this deal-

      http://www.autopartswarehouse.com/sk...ings+Clearance

      It's on clearance and I assume Behr is a good brand but does it have a clutch? I can't really tell and the low price makes me suspicious. I have a feeling it doesn't fit my Jetta....

      I have more trust in FCPGroton, they have a pretty good deal going on an Omega compressor and everything there is 15% off for the next week. http://www.fcpgroton.com/product-exe...category_id/67

      Think I should get an expansion valve too?
      2002 Audi TT Quattro roadster, white, baseball glove seats, 19" aftermarket rims, Pioneer HU with Rockford Fosgate/MB Quart speakers.
      '99 Jetta GLX. Rebuilt AAA VR6 (blown head gasket), Black Forest Stage 2 PEM, Autotech 262 cams, VWVortex's airbox mod with K&N filter, deleted cat and suitcase muffler, Pioneer HU, 17" rims.

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      03-12-2011 01:39 PM #16
      The first photos of the Behr compressor show the wrong compressor for the car. But Behr is good stuff, if you would be getting the right part (not the one in the photos).

      The 2nd compressor looks correct. The expansion valve may be the actual problem and not the compressor. If you want to fix the problem for sure, you need to replace the compressor and the expansion valve at the same time. And get a new drier while you're ordering parts. Most Suppliers will not warranty a compressor unless the drier is replaced at the same time, because when a compressor dies, the drier catches all the crap that the compressor pukes out.

    17. 04-29-2011 07:01 PM #17
      You have a faulty Refrigerant Control Valve, not A Failed Compressor. click this link,

      http://www.aircondition.com/tech/questions/53/

      and go to the bottom of the page and click the PDF file. It will explain everything in detail. good luck!
      96 GTI VR6.

    18. Member Govt-Cheese's Avatar
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      05-30-2011 06:46 PM #18
      As far as I could tell, that refridgerant control valve is part of the compressor. I had already ordered a new compressor from FCP so I installed that today along with a new dryer and expansion valve along with three cans of r134 and some oil.

      Presto! Cold air. Very cold air

      Thanks for the help guys!
      2002 Audi TT Quattro roadster, white, baseball glove seats, 19" aftermarket rims, Pioneer HU with Rockford Fosgate/MB Quart speakers.
      '99 Jetta GLX. Rebuilt AAA VR6 (blown head gasket), Black Forest Stage 2 PEM, Autotech 262 cams, VWVortex's airbox mod with K&N filter, deleted cat and suitcase muffler, Pioneer HU, 17" rims.

    19. Member Govt-Cheese's Avatar
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      05-31-2011 05:23 PM #19
      BTW anyone know about other car AC systems? I'm looking at my friends 98 Civic, it sounds similar to my previous problem. It's not cooling at all. Compressor does come on, whether on or off the low side of AC is off the scale, high side is 120 psi. Sound like a compressor to you?
      2002 Audi TT Quattro roadster, white, baseball glove seats, 19" aftermarket rims, Pioneer HU with Rockford Fosgate/MB Quart speakers.
      '99 Jetta GLX. Rebuilt AAA VR6 (blown head gasket), Black Forest Stage 2 PEM, Autotech 262 cams, VWVortex's airbox mod with K&N filter, deleted cat and suitcase muffler, Pioneer HU, 17" rims.

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