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    Thread: a/c not working, diagnostic steps?

    1. Global Moderator John A's Avatar
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      05-02-2003 11:49 PM #1
      the a/c in my 2k1 jetta 1.8t isn't working -- just never gets cold...

      tried to add a can of refrigerant, but it wouldn't take it...

      it doesn't seem like the compressor is turning on -- even though vag-com shows AC HIGH and compressor on when i switch it on....

      i'm assuming that the refrigerant is low, and that is keeping the compressor from turning on -- but it also won't take any without the compressor going on.

      normally we'd just jump out a switch and force the compressor on, but i couldn't figure out how.

      any ideas? anything else i should be checking?


    2. Global Moderator John A's Avatar
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      05-04-2003 05:08 PM #2
      bump!

    3. Moderator Mike0105's Avatar
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      05-04-2003 05:51 PM #3
      no clue John...might want to give chris or pat a call and ask them for some help
      Mike

    4. Global Moderator John A's Avatar
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      05-04-2003 05:59 PM #4
      yeah... this one's going to be ugly i think. i guess a/c isn't part of powertrain, eh? maybe it's time to trade it in.


    5. 05-05-2003 12:13 AM #5
      Hey John,
      My Wife's New Beetle has just been bitten by a similar thing- except when I press the AC button, the AC compressor doesn't come on and Vag-com aggrees-- the compressor is shown as off.

      I was cruisin the Bentley this evening and it looks like there are a few hidden switches in there... one will not let the compressor turn on if it's too cold, and the other won't let it turn on if there is too much/ too little refridgerant in the system.
      There's a quick test to be made, by jumping pins 1 and 2 of the sensor in the far back passenger side of the engine compartment. I couldn't reach it real easy tonight (had a flashlight in one hand), but I'll see if I can get to it tomorrow.

      -chris


      Modified by oldskool industries at 12:14 AM 5-5-2003


    6. 05-05-2003 07:35 AM #6
      Ok I just did this the other day.....
      Jump out and check if when you turn the AC on if your compressor turns on or the Fans? If not. Check the PLUG that comes off the top of the battery you should be able to use a test light and should get 12v from all 3 or 4 pins (think it's 3). If you have power there, those wires run striaght to your relay which is under your battery. It's pretty big costs about $170 if it's bad. If the blower comes on it's going to be one of those or the compressor. Turn the AC on and test light the plug for the compressor, you should see 12v. If not, it's one of the things listed. Also check your high and low pressure switches if they are bad the compressor will not turn on, However check the other things I mentioned earlier first. ALso there is a temp switch that is in the same area of the car as the relay. It's a big sensor that is on the radiator endcap I think. Check for 12v there. That basically sums up the WHOLE AC electrical system for the compressor.

    7. 05-05-2003 12:19 PM #7
      let me know what you find

    8. Global Moderator John A's Avatar
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      05-05-2003 12:31 PM #8
      we tried jumping out what i thought was a pressure switch near the firewall on the pass side this past weekend. we proceeded to blow a fuse, and stopped going down that route. i'll see what i can find out this week.

    9. 05-05-2003 03:52 PM #9
      1. check to see if your AC compressor is engauging. If it isn't it's either 2 things, there is not 134a in the system because of a leak, or you have a bad relay. Before wasting your time checking relays, take a small screw driving and quickly push in/out on one of the high side or low side lines (just unscrew either the big or small cap on the ac lines. If a weak mist comes out, your system is probably empty due to a leak, if a quick burst comes out it's probably full and you have an electrical problem.

      If there is no 134a check for the obvious, a hole in your condensor (infront of the radiator) all it takes is a small pebble at 100mph to put a hole in it. Look for oil spots and paint coming off on spots on your condensor, if you get a 134a sniffer it will be alot easier. If you can't find any leak you're going to have to get a certified shop to put die in the system.

      If there is 134a start by checking all the fuses. If there good switching the AC compressor clutch relay with one just like it and see if the compressor turns on. If it doesn't, get the ETM and jump the relay, if it doesn't turn on, there is either a wiring problem after the relay, or in the Electrical part of the comrpessor clutch. If it does turn on, the problem is either the relay, or an electical problem before the relay (wiring, switch)

      Hope this helps. Don't smoke when you're checking to see if there is 134a

      marty


    10. Global Moderator John A's Avatar
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      05-07-2003 10:17 PM #10
      i'm hopefully going to do some of these steps tomorrow, will report back...

    11. 05-07-2003 10:34 PM #11
      I have the same problem, nothing happens when i push the a/c button. I also have the same problem with the cruise control.
      R32 NA 13.2@103
      R32 HPA 11.8@121

    12. 05-07-2003 11:13 PM #12
      Guys I looked at 3 other NB's today and all but the newer 2002 had the power distribution panel on the top of the battery was just fried. Had another buddy that the relay went out in his car yesterday. Similar symptoms. Blower blows, just no cool air. Clutch doesn't engauge and now power to compressor. Traced it all the way back to the relay. Power going to relay, and switch was being turned on, just relay wasn't clicking on.

    13. Global Moderator John A's Avatar
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      05-09-2003 10:30 PM #13
      first update: system has pressure, i touched the valve with something and it shot out at me....

      distribution block was fine, all fuses were good and looked fine.

      where is the relay? i can check that tomorrow....


    14. 05-10-2003 07:24 AM #14
      relay is directly under the battery....I really think it's that because your not getting power to the Fans or the compressor right? When you turn the AC on high your fans for the radiator don't turn on high? Relay will be really big with 2 plugs going into it. I think on has like 7 wires while the other has 4 heavy gauge wires.

    15. Global Moderator John A's Avatar
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      05-10-2003 05:23 PM #15
      took out my airbox and battery today to find the relay, but came up empty handed.... here's a pic:

      where's the relay ?




      Modified by John A at 9:16 AM 5-11-2003


    16. 05-10-2003 06:18 PM #16
      You get to it from the bottom of the car. Should be Under there, but from the bottom of the car. Follow the plug connector down from the top of the battery distrobution panel should go right to it.

    17. 05-10-2003 06:32 PM #17
      bug power is talking about the fan control module it is possibly faulty but first remove the fuse on top of the battery some times they will show voltage but will be blown inside the fuse its hard to explain but it will look melted you should back probe the a/c wir with 12 volts and see if it engages and does it they blow cold if not you could be low on freon the system wont work with a low charge

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      05-10-2003 09:00 PM #18
      You may also want to check the low pressure sensor. I forgot to plug mine back in after installing my FMIC this winter. The fans would run but the compressor never engaged because the sensor is designed to protect it in case of a leak.

    19. Global Moderator John A's Avatar
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      05-10-2003 10:01 PM #19
      ok, i get no fans, no compressor. i'll get under the car tomorrow to look for it.

      thanks!


    20. 05-11-2003 03:19 AM #20
      Before you get under the car. Hook the battery back up, then unplug the connector that goes into the power distro box on top of the battery. Use a test light to make sure ALL of those pins are hot. If they are....the next stop is the Fan Relay under the battery that must be accessed from under the car.

    21. Global Moderator John A's Avatar
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      07-05-2003 10:18 AM #21

    22. 07-05-2003 10:32 AM #22
      Good to hear you got it fixed. Now if you have the equipment, you can clean that one up and get it working again. If your just going to throw it away, you may be able to get a couple bucks for it. When putting it back together just use some silicone RTV to seal it all up.

    23. 07-05-2003 08:46 PM #23
      Quote, originally posted by oldskool industries »
      Hey John,
      My Wife's New Beetle has just been bitten by a similar thing-

      Ours turned out to be a cracked condenser. We had a rodent commit suicide thru our grill last year and his impact must have put a slow leak in the compressor.
      I'm waiting for her new 'cup car' bumper to arrive before I fix it so I can take apart the nose of the car once.


    24. Global Moderator John A's Avatar
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      07-07-2003 04:08 PM #24
      thanks again rodney, this was a good thing to avoid a trip to the dealership on. (although my cracked coilpack wires -- now THAT it's going in for!)

      bump for the weekday crew.


    25. 07-07-2003 04:19 PM #25
      brutal.

      glad to hear it's fixed! nice how-to


    26. 05-06-2011 06:06 PM #26
      Quote Originally Posted by John A View Post
      Any chance you might be able to repost this? I have a 2002 Jetta that I think has the relay switch problem. Leads off the battery are hot, but the compressor is not getting any juice to it. Can't quite seem to figure out where the problem might be between the battery and the compressor.

    27. 05-06-2011 06:26 PM #27
      Quote Originally Posted by fetter View Post
      Any chance you might be able to repost this? I have a 2002 Jetta that I think has the relay switch problem. Leads off the battery are hot, but the compressor is not getting any juice to it. Can't quite seem to figure out where the problem might be between the battery and the compressor.
      OK, I found this write up on your website, however, exactly where is the fan control module located on a 2002 jetta?

    28. Member
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      05-07-2011 06:47 PM #28
      fan control module part# 1jo919506k. search it at www.ecstuning.com. you'll see how it looks like.

      Quote Originally Posted by fetter View Post
      OK, I found this write up on your website, however, exactly where is the fan control module located on a 2002 jetta?

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      05-08-2011 01:57 AM #29
      thanks for this elect. wiring diagnosis, it pretty much sum it up and made it easier knowing what to do in ur own garage if u have a tester

    30. 03-15-2012 08:42 AM #30
      Hi !

      I have the same kind of problem with my 1.8T 2003 Jetta.
      However, I noticed that my fans are no longer coming off when the temp is coming high. Is this related and is it due to a bad Fan control module ??

      Thanks for your advices

      Cheers

    31. Member brett1220's Avatar
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      03-15-2012 09:00 AM #31
      my AC doesnt work also but its not the compressor or the or any mechanical problem, its because the rubber line that comes from the compressor has been rubbing the the rad fan support for years and it eventually rubbed a hole in it so is their anyway i can patch it up?

    32. 05-31-2012 08:55 AM #32
      Hi,

      I have a 2000 Jetta TDI that had a bad compressor. I bought a pre-loaded compressor this winter and installed it. I changed all my o rings, my evaporator and my expension valve.

      When I press on my ac button, the compressor won't engage at all. Since it came with the oil already in it, I don't want to add any more. How can I add "air" into it to build up the pressure? Seems like it doesn't see that it's full already.

      Thank you for your help.

    33. 05-31-2012 10:18 PM #33
      Well, I had the pleasure of leaving work on a 95+ degree day this afternoon... only to find out my AC was not working

      after checking fuses, both on the side of the dash and on top of the battery,

      I pulled the battery out to look at the fan control module, which i pulled apart to find a lot of rusty stuff in there so i sprayed it with electrical cleaner .. tested it... it worked fine, so i rtv siliconed the cover back on... but my compressor would still not kick in

      for some reason, i was impelled to wiggle the 3 green fuses that sit above the battery, when i heard the auxiliary water pump turn off and on

      I was like WTF?!?!?... so i pulled the fuse to find that one of the legs of the fuse was totally corroded ... i cleaned it up... fired up the car , turned the AC on AND SON OF A BITCH the AC worked

      not saying that this would fix all of yours problems, but it fixed mine

    34. 06-03-2012 09:34 AM #34
      i had a similar issue. i just spent 400 dollars on AC parts and had it recharged with die an all at work (im a tech for international) then my fiance was driving the GTI home last night and it never got cold compressor never kicked on i was ready to kill something then this morning i googled the problem and this site came up. i went out and pulled the fuses on top of the battery and sure enough even though they check out good by looking down on them from the top one of the legs had a little corrosion i cleaned it up and sure enough compressor and everything kicked back on. i do however have a coolant leak by the water outlet on the right side of the head i need to address now.

    35. n00b
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      08-27-2013 01:50 PM #35
      I'm suspecting a bad Fan Controller Module on my 2004 Jetta 1.8T. Fans are running fine but the clutch doesn't engage. I got 9.6V measurement on the AC Clutch power connector. So there is power however is it enough to activate the AC Clutch? It should be 12V correct?

      I'm trying to remove the Fan Controller Module but I can't find the mounting bolt under the battery plate. There's a bunch of electrical harness covering the mounting bolts. They're pretty tight, how did you move the electrical harness out of the way to remove the mounting bolt of FCM? Please click on the link below for reference. Thanks!

      http://forums.tdiclub.com/showthread.php?t=281684

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