VWVortex.com - Fuse 16 Keeps blowing
Username or Email Address
Do you already have an account?
Forgot your password?
  • Log in or Sign up

    VWVortex


    Results 1 to 24 of 24

    Thread: Fuse 16 Keeps blowing

    1. Member lite1979's Avatar
      Join Date
      Sep 8th, 2005
      Location
      North Buffalo
      Posts
      1,869
      Vehicles
      2001 Audi TT 225 QC
      08-09-2019 03:47 PM #1
      *** Edited ***

      As stated in the title, Fuse 16 keeps blowing in my 2001 Audi TT Quattro Coupe 225. The fuse basically powers the Fan Control module, so it's used for the magnetic clutch on the A/C compressor and the after-run coolant pump on our cars. It also supplies power to the G65 A/C pressure switch (this can be confusing, as the VCDS scan will always say F129 switch open circuit - G65 is a newer version of F129 with three wires instead of four).

      I've checked continuity from the magnetic clutch to the Fan Control Module, and it's fine. Same for the after-run coolant pump and the G65 A/C pressure switch.
      Last edited by lite1979; 09-10-2019 at 01:04 PM.
      You can remove blood stains with hydrogen peroxide.

    2. Remove Advertisements

      Advertisements
       

    3. Member lite1979's Avatar
      Join Date
      Sep 8th, 2005
      Location
      North Buffalo
      Posts
      1,869
      Vehicles
      2001 Audi TT 225 QC
      08-13-2019 03:17 PM #2
      For what it's worth, I'm investigating this. The wiring diagram with this fuse in is is on page EWD-79 of my Bentley manual, and it shows the following:

      J293 (Fan Control Module) to a red/grey wire
      red/grey wire to Fuse 16 (10 Amps)
      Fuse 16 to red wire to A98 = plus connector -4- (30) in instrument panel wiring harness
      red wire to B156 = Plus connector -4- (30) in wiring harness interior
      You can remove blood stains with hydrogen peroxide.

    4. Member
      Join Date
      Aug 5th, 2002
      Location
      WA State
      Posts
      270
      Vehicles
      03 TT225, 76 Dasher 16V
      08-15-2019 09:17 AM #3
      Curious what you've tried.

      Have you tried not having your AC on, (keep it on "economy") for a while? If so, does it still blow the fuse?

      If fuse stays good, does it immediately blow when turning on AC?

      Have you verified if the AC is actually working?

      Obviously all those questions are 100 percent related. That's where I'd start.

    5. Remove Advertisements

      Advertisements
       

    6. Member lite1979's Avatar
      Join Date
      Sep 8th, 2005
      Location
      North Buffalo
      Posts
      1,869
      Vehicles
      2001 Audi TT 225 QC
      08-16-2019 12:46 PM #4
      Thanks for asking!

      Edit: Fuse blows and battery dies whether or not I have A/C on.

      A/C does not work.

      What I've done so far:

      replaced the F129 switch

      replaced the radiator fans

      replaced the radiator thermo-switch for the fans

      replaced the Fan Control Module under the battery

      replaced fuse 16 several times now

      checked the voltage between pins 1 and 3 for the F129 switch with A/C on; voltage jumped around and the battery died very quickly after that.
      Last edited by lite1979; 08-19-2019 at 12:02 AM.
      You can remove blood stains with hydrogen peroxide.

    7. Member lite1979's Avatar
      Join Date
      Sep 8th, 2005
      Location
      North Buffalo
      Posts
      1,869
      Vehicles
      2001 Audi TT 225 QC
      08-24-2019 02:55 PM #5
      Checked resistance at the A/C clutch coil, and it's good - 3.8 Ohms. Checked at the after-run coolant pump as well, but I'm not sure what that's supposed to be - came out to 1.2 Ohms.

      Still feels like looking for a needle in a haystack, but I'm thinking of borrowing one of those powered current checkers now - apply power to the fuse location, then use a tracer to see where it stops. I've seen people use them on youtube videos, but I've never used one myself...
      You can remove blood stains with hydrogen peroxide.

    8. 08-24-2019 10:09 PM #6
      I would check your wiring to the alt and pump. This sounds like you have a wire grounding.


      Sent from my iPhone using Tapatalk

    9. Member lite1979's Avatar
      Join Date
      Sep 8th, 2005
      Location
      North Buffalo
      Posts
      1,869
      Vehicles
      2001 Audi TT 225 QC
      08-28-2019 03:02 PM #7
      I agree. I definitely have a short to ground, and that's what's blowing my fuse.

      Wiring for the alt looks good, but I haven't taken it apart (it's bundled with the wiring for the A/C clutch coil, wrapped in a tight rubber tube).

      Wiring for the after-run coolant pump looks good, too, but it joins up with a bunch of other wires on the other side of the motor, so I'm still trying to figure out where the two sides meet. I think it's behind the motor somewhere, and I did do a bunch of work back there between rebuilding the turbo and replacing the downpipe/cat.

      I've also had the transmission and bevel box out twice in the last few years, but all the wires on TOP of the transmission look good.

      I hope we have today's weather again tomorrow, as I have the whole day 'off'. I still have to work from home, but I don't have to tend bar.
      You can remove blood stains with hydrogen peroxide.

    10. Member lite1979's Avatar
      Join Date
      Sep 8th, 2005
      Location
      North Buffalo
      Posts
      1,869
      Vehicles
      2001 Audi TT 225 QC
      08-30-2019 04:36 PM #8
      So I started testing continuity from G65 (a/c pressure switch), N25 (a/c clutch coil), and V51? (not sure; manual's not in front of me, but it's the After-Run Coolant Pump.

      I basically set my multimeter to continuity, and watched the numbers drop as I confirmed known grounds, and supposed open circuits.

      They all report no continuity on positive, no continuity on data, yes continuity on ground (I used the intake manifold for my ground in each case as it's right there).

      Remove battery, remove battery tray, remove new-ish J293 (Fan Control Module). 14-wire plug looks clean. 4-wire plug looks clean.





      I mocked the J293 (Fan Control module) back up in its installed position, and I can say that this wire was definitely touching the frame right next to it.

      I plan to put everything back together tomorrow and see what's good, but I bought five new fuses just in case.

      Edit: Not sure what's up with sharing a google image on here, but I'll fix it eventually so you can see the open wire.
      Last edited by lite1979; 09-05-2019 at 01:01 PM.
      You can remove blood stains with hydrogen peroxide.

    11. Member lite1979's Avatar
      Join Date
      Sep 8th, 2005
      Location
      North Buffalo
      Posts
      1,869
      Vehicles
      2001 Audi TT 225 QC
      08-31-2019 01:14 PM #9
      Can someone tell me if the picture above is visible?
      You can remove blood stains with hydrogen peroxide.

    12. Member lite1979's Avatar
      Join Date
      Sep 8th, 2005
      Location
      North Buffalo
      Posts
      1,869
      Vehicles
      2001 Audi TT 225 QC
      08-31-2019 02:39 PM #10
      After wrapping that up and putting everything back together, I'm still blowing fuse 16.

      Fuse 16 blows as soon as I turn the ignition on, in fact.

      I'm wondering if the short circuit fried my Fan Control module...
      You can remove blood stains with hydrogen peroxide.

    13. Member skills@eurocarsplus's Avatar
      Join Date
      May 27th, 2004
      Location
      Groton, Connecticut
      Posts
      2,443
      08-31-2019 03:27 PM #11
      Quote Originally Posted by lite1979 View Post
      Can someone tell me if the picture above is visible?
      no photo on my end.

      if it's blowing on key on, it has to be a dead short. see what is on the 15 feed for that circuit (15 is key on +, 30 is + whenever the battery is hooked up etc)

    14. Member lite1979's Avatar
      Join Date
      Sep 8th, 2005
      Location
      North Buffalo
      Posts
      1,869
      Vehicles
      2001 Audi TT 225 QC
      09-02-2019 07:11 PM #12
      Thanks. I'm thinking my short may be in the dashboard, then.
      You can remove blood stains with hydrogen peroxide.

    15. Member lite1979's Avatar
      Join Date
      Sep 8th, 2005
      Location
      North Buffalo
      Posts
      1,869
      Vehicles
      2001 Audi TT 225 QC
      09-03-2019 04:28 PM #13
      So though I fixed that wire, I think there's still a short inside my Fan Control Module. Once I disconnected it, Fuse 16 stopped blowing.

      The module is relatively new, but I think that bad wire messed up the FCM since I didn't know about the short...
      You can remove blood stains with hydrogen peroxide.

    16. Member skills@eurocarsplus's Avatar
      Join Date
      May 27th, 2004
      Location
      Groton, Connecticut
      Posts
      2,443
      09-03-2019 09:57 PM #14
      sounds like you're on the right track. you don't have a stuck fan do you? as in, the fan itself could be internally shorted

    17. Member lite1979's Avatar
      Join Date
      Sep 8th, 2005
      Location
      North Buffalo
      Posts
      1,869
      Vehicles
      2001 Audi TT 225 QC
      09-05-2019 01:10 PM #15
      Image fixed. Had to create an imgur account, but I hope to be more active on here to make it worth it.

      Both fans spin just fine (and they're only three years old at this point).

      I'm waiting for a new FCM to come in the mail, then hopefully I can mark this thread as solved.

      What happened, if I understand correctly, is that wire was touching the frame, and in turn fried my Fan Control Module. I didn't know this was the reason my fans were staying on after shutting the car off, so I was checking for a parasitic drain.

      Naturally, in my process of checking for a parasitic drain, pulling fuses at night time checking to see if the amperage draw went to zero didn't help, because when I pulled fuse 16 it was already blown.

      When fuse 16 blows, the car makes the fans run all the time, because the Fan Control Module isn't in control anymore, and it's better to have a dead battery than to have a warped head from overheating, I guess.

      I replaced a bunch of stuff thinking the parts were bad, like my G65 A/C pressure switch (at the recommendation of the place that charged up my refrigerant). They were able to apply 12V to the A/C clutch coil and get cold air, so I figured either the radiator thermo-switch was bad or the FCM was bad. I replaced both, and still couldn't get cold air, and that's when I read about fuse16 and how the fans work if it's removed/blown.

      Hopefully I don't have to replace either the G65 or the radiator thermo-switch again once the new FCM comes in. I'll update when I get it.
      You can remove blood stains with hydrogen peroxide.

    18. Member lite1979's Avatar
      Join Date
      Sep 8th, 2005
      Location
      North Buffalo
      Posts
      1,869
      Vehicles
      2001 Audi TT 225 QC
      09-07-2019 05:28 PM #16
      Update:

      New FCM came in today. Installed it, hooked up the battery, fuse 16 blows. Grrr.

      Pulled the 30A fuse for the fans on top of the battery - fuse 16 does not blow. At this point, I think my short to ground has to be between the FCM and the fans. Am I right?
      You can remove blood stains with hydrogen peroxide.

    19. Member skills@eurocarsplus's Avatar
      Join Date
      May 27th, 2004
      Location
      Groton, Connecticut
      Posts
      2,443
      09-07-2019 08:58 PM #17
      Quote Originally Posted by lite1979 View Post
      Update:

      New FCM came in today. Installed it, hooked up the battery, fuse 16 blows. Grrr.

      Pulled the 30A fuse for the fans on top of the battery - fuse 16 does not blow. At this point, I think my short to ground has to be between the FCM and the fans. Am I right?
      that's why I asked about the fans...

      even if they spin, they could be internally shorted (low speed to high, low to ground etc)

      I would put it all back together, put in all fuses, FCM etc and disconnect the fan(s) if the fuse(s) don't blow I would suspect the fan(s) are NFG

    20. Member lite1979's Avatar
      Join Date
      Sep 8th, 2005
      Location
      North Buffalo
      Posts
      1,869
      Vehicles
      2001 Audi TT 225 QC
      09-10-2019 12:48 PM #18
      Fuse 16 still blows with the radiator fans disconnected (at the two 3-wire junctions, one female, one male).

      I'm going to inspect the wires going from T4 to its respective endpoints. Wondering if the radiator thermo-switch could be internally shorted?
      You can remove blood stains with hydrogen peroxide.

    21. Member lite1979's Avatar
      Join Date
      Sep 8th, 2005
      Location
      North Buffalo
      Posts
      1,869
      Vehicles
      2001 Audi TT 225 QC
      09-10-2019 05:40 PM #19
      Disconneting the radiator thermo-switch STILL blows the fuse.
      You can remove blood stains with hydrogen peroxide.

    22. Member lite1979's Avatar
      Join Date
      Sep 8th, 2005
      Location
      North Buffalo
      Posts
      1,869
      Vehicles
      2001 Audi TT 225 QC
      09-10-2019 05:46 PM #20
      Just disconnected the T4 from the FCM and tried again - fuse does not blow when T4 is disconnected. I think this suggests that the wires from T4 are grounded somewhere.
      You can remove blood stains with hydrogen peroxide.

    23. Member lite1979's Avatar
      Join Date
      Sep 8th, 2005
      Location
      North Buffalo
      Posts
      1,869
      Vehicles
      2001 Audi TT 225 QC
      09-10-2019 07:24 PM #21
      I'm still tracing the wires, and I don't see any clear evidence of shorts to ground. I'm behind the left headlight now, and this ground kind of stuck out to me:

      You can remove blood stains with hydrogen peroxide.

    24. Member lite1979's Avatar
      Join Date
      Sep 8th, 2005
      Location
      North Buffalo
      Posts
      1,869
      Vehicles
      2001 Audi TT 225 QC
      09-10-2019 09:22 PM #22
      I'm losing my mind on this one.

      I traced all four wires from T4 at the FCM to their respective destinations, and not one of them shows any sign of touching ground, anywhere.
      You can remove blood stains with hydrogen peroxide.

    25. Member
      Join Date
      Aug 5th, 2002
      Location
      WA State
      Posts
      270
      Vehicles
      03 TT225, 76 Dasher 16V
      09-11-2019 09:35 AM #23
      You'll figure it out eventually. So many of us have been there for one reason or another. Wish I had more than just words of encouragement.

    26. Member lite1979's Avatar
      Join Date
      Sep 8th, 2005
      Location
      North Buffalo
      Posts
      1,869
      Vehicles
      2001 Audi TT 225 QC
      09-11-2019 03:11 PM #24
      I was thinking, since it doesn't blow until I turn the ignition on, maybe I'm looking at this the wrong way.

      Ignition switch goes to Plus connection (15) in instrument panel wiring harness on a 2.5mm black wire.

      That black wire goes to fuse 5 (7.5 amps - fuse is fine) on the left of the dash. - if the fault were in this circuit, the 7.5 Amp fuse would blow, correct? It doesn't though, so I think that once the fan relay in the FCM is activated, that's what causes fuse 16 to blow. Low power from ignition activates the relay, high power from the fan circuit goes back through the FCM to a peripheral with no resistance, which in turn blows the fuse.

      From the fuse panel, a 0.5mm black/blue wire goes to B135 connector inside dash board, and splits to both G65 in the engine bay (A/C pressure switch), and T17 behind instrument panel > D/9 at the HVAC control head.

      I'll trace the wires from the ignition switch and report my findings. It's also possible that the G65 wiring is to blame, since that's on the same circuit, but when I tested for continuity on the G65 connector, ground was continuous, and neither the data nor the hot wire showed continuity to ground. Perhaps that because the ignition was off when I tested.
      Last edited by lite1979; 09-13-2019 at 02:35 PM.
      You can remove blood stains with hydrogen peroxide.

    Posting Permissions

    • You may not post new threads
    • You may not post replies
    • You may not post attachments
    • You may not edit your posts
    •