30A fuse for fans blowing after replacing fuse box and alternator cable

tgray

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Yes I have found the same thing and good to just have a spare or put a new on in when you have these difficult issues to trouble shoot. I have found the cheap ebay ones to do quite well for me over the years as sometimes the used ones have their own issues.
 

bobla

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Williamsburg, Virginia
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2004 Jetta GLS, Silver
2004 Golf GL, Manual, 200K miles.

The backstory: I had the relatively common battery top fuse box melting problem recently where the 30A fuse slot for the fans over heats and melts. I bought and installed a replacement fuse box from IDParts about a month ago. I also up-sized and replaced the main alternator cable at that time -- discussions around the fuse box melting issue suggested that replacing the alternator cable is a good preventive measure in terms of lowering resistance and keeping things cooler. I should also note that I replaced both fans a year or two ago. Both fans work great currently. Oh, and I cleaned up all of the grounds under the battery box when I put in the new fuse box though they all looked pretty darn good. PNW car -- not much corrosion.

So the 30 amp fuse in the battery top fuse box that controls the fans blew today and I'm a little uncertain where to start with troubleshooting this. I replaced the fuse on the side of the road and the AC and fans operated just fine during the 20 minute drive back home. I cannot see any new melting/burning issues with the new fuse holder. AC works well and is cold. Both fans work when doing the fan test.

Since it's the 30A fuse for the fans that blew and it's slot was previously burned, should I start by checking all of the wiring to those fans? Could the alternator (or more likely) the regulator be the problem?

Open to any and all suggestions on where to start with this.

I tried to attach a photo of my fuse block but no joy. Cut/paste and drag/drop unsuccessful from PC being used to draft this post.

Thanks up front!
"The backstory: I had the relatively common battery top fuse box melting problem recently where the 30A fuse slot for the fans over heats and melts. I bought and installed a replacement fuse box from IDParts about a month ago. I also up-sized and replaced the main alternator cable at that time -- discussions around the fuse box melting issue suggested that replacing the alternator cable is a good preventive measure in terms of lowering resistance and keeping things cooler. I should also note that I replaced both fans a year or two ago. Both fans work great currently. Oh, and I cleaned up all of the grounds under the battery box when I put in the new fuse box though they all looked pretty darn good. PNW car -- not much corrosion. "

I have the same issue. I have purchased the fuse box from ID Parts. What gage cable did you upgrade to and where did you obtain it?
 

OlyTDI

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Olympia, WA
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'04 Golf
"The backstory: I had the relatively common battery top fuse box melting problem recently where the 30A fuse slot for the fans over heats and melts. I bought and installed a replacement fuse box from IDParts about a month ago. I also up-sized and replaced the main alternator cable at that time -- discussions around the fuse box melting issue suggested that replacing the alternator cable is a good preventive measure in terms of lowering resistance and keeping things cooler. I should also note that I replaced both fans a year or two ago. Both fans work great currently. Oh, and I cleaned up all of the grounds under the battery box when I put in the new fuse box though they all looked pretty darn good. PNW car -- not much corrosion. "

I have the same issue. I have purchased the fuse box from ID Parts. What gage cable did you upgrade to and where did you obtain it?
Here is the link to the guy who makes the cables. I went with the heavier red cable.

Mk4 Alterator Cable
 

csstevej

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2001 golf tdi 4 door auto now a manual, mine, 2000 golf 2 door M/T son's,daughters 98 NB non-TDI 2.0, 2003 TDI NB for next daughter, head repaired and on road,glutton for punishment got another tdi 2001NB,another yellow tdi NB
You can also get them made by a member from here by the name Mozambiquer , I recently bought two cables from him for this reason too, niece quality and fast response and delivery. Just my .02.
 

OlyTDI

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You can also get them made by a member from here by the name Mozambiquer , I recently bought two cables from him for this reason too, niece quality and fast response and delivery. Just my .02.
Excellent! Good to know -- thanks!
 

OlyTDI

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UUUUUGGGGHHHHH...

Resurrecting this thread with a plea for advice before self harm ensues.

After replacing the Fan Control Module and having a blissful 10 days or so of AC comfort, the S180 fuse blowing has returned. Got in the car this morning, turned on the AC while driving and I could tell immediately that the fuse had blown (no mini-lag from compressor kick-in, warm air at vents). I pulled over and sure enough, it was blown. Replaced fuse, blew again immediately. I don't know whether the old FCM was bad. When I replaced it with the current one (used and provided by a member), I did get 10 days of operation out of the AC before the problem returned. This would suggest that the FCM was the culprit as I had gotten no where with any other diagnostics. But what are the chances of the second FCM just happening to go bad as well? There's a problem and I admit defeat on how to find it.

I'm at my wits end here and need some advice. This is the first time in my nearly 50 years of fixing my own vehicles that I've had an electrical problem that I couldn't solve myself. But I am at the end of my capability with this. As such, where should I take this car to be looked at? VW dearlership? Local "German" car repair? AC specialist? I feel like a sheep heading for slaughter.

I'm of course most worried about someone simply throwing parts at it until it either is fixed or I go broke. AC systems aren't something you want to play that game with.

Anyway, short of using explosives, what is the best path forward here?
 
Last edited:

OlyTDI

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Please give this another analytical look folks -- I really could use the diagnostic help!

Spent the entire day starting from scratch on this. Forget what's been writen prior. Here's what I know:

2004 Golf BEW TDI

Problem: S180 fuse blows (fuse block atop of battery) when AC is activated (AC button pushed and cabin blower on) but only with the engine running – it cannot be made to happen with the engine off. This problem is intermittent but frequent. I can go days between fuse blowing episodes or blow a dozen fuses in a row. Also, it occurs only when activating the AC – it does not happen once the AC has already made it through being activated, however if I turn off the engine, it will next occur only during AC activation at some point in the future. On those occasions when I turn on the AC and the fuse does not blow, the AC is nice and cold. So essentially, everything works as it should except that frequently, when the engine is running and the AC is engaged, that S180 fuse will blow immediately upon AC engagement – there is no lag to the fuse blowing -- happens right away on compressor activation.

The clutch coil shows about 3.5 ohms of resistance measured at the harness connector.

I can find no shorts in the wiring between a) fuse S180 and the coolant thermo switch, b) in either of the two cooling fan harnesses, c) in either of the two fan control module harnesses, or d) in the compressor clutch coil harness. I used the instructions from “A4 Coolant Fan testing, MANUAL Air Conditioning - REV 7 6/18/2009 referenced in the “check your AC fan function sticky” as the methodology.

I have replaced the fan control module with no change.

Both cooling fans are about 2 years old. I have tested them by jumping and with direct power. Both are functioning perfectly on both low and high speeds. Both fans show between 0.7 – 0.9 ohms when measuring across the pins at the fan motor harnesses (pin 1 to 2; 1 to 3; 2 to 3).

Both fans come on at low speed with engine off / AC button on / cabin blower on – as they should.

The battery top fuse box was installed in May after the (commonly reported) melting of the box at the S180 fuse slot. I also replaced the alternator cable to the top fuse box at that time with a larger gauge over-sized cable.

The alternator is functioning as it should.

I believe that I have essentially eliminated:

- the fans and their harnesses

- wiring (I can’t find any suspect wiring, dead shorts, or make anything short to ground with wiggling)

- the FMC

- the coolant thermo switch

My impression is that this problem must be related to either an intermittent short along the clutch coil cable or at its plug connection, or perhaps an intermittent clutch or coil problem causing a resistance spike on compressor start up. This fuse-blowing problem requires two things to occur – the engine must be running and the AC must be activated (cabin blower on with AC switch on) and it then either blows immediately or, if it doesn't blow, won't while the AC is running once it makes it through compressor start up. I don’t have the diagnostic tools/know how to troubleshoot the compressor (AC high/low pressure), etc., if that’s even a possibility of being the problem. It just seems to me as though there is some source of resistance that sometimes rises to the level of blowing the fuse on engaging the AC compressor.

Could a failing clutch or coil cause this and if yes, intermittently?

Where would you go from here? What have I overlooked?

I am prepared to take it in to a shop 10 days from now and if I can't find the problem, want to at least help them by focusing on a particular area.

Thanks very much for the assistance -- this is a bugger!
 

P2B

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Could a failing clutch or coil cause this and if yes, intermittently?
In theory yes, although I have never seen it.
Where would you go from here? What have I overlooked?
Seems to me you have fairly definitively isolated the problem to compressor engagement, so I would try swapping out the coil - but then I have spares on the shelf.
 

OlyTDI

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In theory yes, although I have never seen it.

Seems to me you have fairly definitively isolated the problem to compressor engagement, so I would try swapping out the coil - but then I have spares on the shelf.
Thanks much for that perspective!

Can the coil be swapped out in place and without discharging the AC system?
 

J_dude

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Thanks!

After I posted that question, I remembered I had actually had looked into the replacement method. I forgot that I had found and saved a a video of the coil replacement on my engine type. He states that you have to evacuate the system and pull the compressor (after pulling the alternator...).

compressor clutch coil replacement BEW
Ohhhh crap, BEW. I thought we were talking ALH, sorry. I need to pay more attention.
That’s CoolAirVW^ btw, a member here as well.
 

OlyTDI

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Ohhhh crap, BEW. I thought we were talking ALH, sorry. I need to pay more attention.
That’s CoolAirVW^ btw, a member here as well.
Yes! No worries!

I emailed CoolAirVW asking whether or not he'd ever encountered the symptoms of my problem ending up being a coil. He said that he hadn't.
 

J_dude

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I've never messed with a BEW. What prevents dropping the compressor out the bottom?
Same here, but I think the power steering pump is below the AC on a BEW. So AC compressor is kinda sandwiched between alternator and PS pump.
 

P2B

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Same here, but I think the power steering pump is below the AC on a BEW. So AC compressor is kinda sandwiched between alternator and PS pump.
Ah - but surely with either the PS pump or alternator out of the way you should be able to swing the compressor enough to swap the coil without evacuating?
 

OlyTDI

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Ah - but surely with either the PS pump or alternator out of the way you should be able to swing the compressor enough to swap the coil without evacuating?
Boy, you got me. I would think that CoolAirVW would have done that had it been possible/advantageous.
 

Zak99b5

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I changed the clutch on my daughter's gasser MkIV Golf without disconnecting the compressor. I believe it's in the same spot as on the BEW.

Remove alt, then you can take the mounting bolts off the compressor. It's NOT a great angle for working on it, but it can be done. I was alone, so I used some wood blocks to support the compressor at an angle so I could get to it. I believe i removed the center nut from underneath (after it was freed), pointing it down. Then angled it up and did the rest from up top.
 

J_dude

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Ah - but surely with either the PS pump or alternator out of the way you should be able to swing the compressor enough to swap the coil without evacuating?
Yeah I guess if Zak did it on a gasser it should be possible on a BEW too.
 

OlyTDI

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Does anyone have any ideas as to where the problem might be? I've got no real reason (beside behavior) that it has anything to do with the clutch or coil.

How would a pro shop approach this?
 

Genesis

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Have you unplugged the compressor clutch connector and then attempted to drive it "as if it was all hooked up" to see if it blows under that circumstance?

I'm skeptical that the actual coil is the problem BUT a short is a short is a short, and you clearly have one somewhere but its not obvious where.
 

OlyTDI

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That's an interesting suggestion, Genesis. No, I haven't unplugged then spent time trying to blow the fuse by turning things on. That certainly would be a good thing to do. I will do that.

Drove around today and got into the vehicle twice engaging the AC. Fuse didn't blow. But that's the pattern -- that there is no pattern!

I'll report back. I appreciate the suggestion!
 

OlyTDI

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Okay, I went ahead and conducted the test that Genesis suggested above -- unplugged the clutch coil cable and drove around turning the AC on...off...on...many times.

It indeed blew the fuse at some point in that effort.

So I think that I can safely say that the compressor and clutch coil/wiring is not the issue. Good.

I don't know how it can be the fans as they operate normally on both speeds and have nominal resistance. Okay.

The FCM was replaced without changing the outcome so it seems that it would also be eliminated. Check.

So am I correct that this has to be a short related to that part of the circuitry that is activated only when the engine is running and only when the the AC is turned on. If I'm correct, that would be a circuit that comes from the FCM though not the FCM itself as that's been replaced without improving the situation.

Assuming I'm dealing with an intermittent short in that circuitry, how would one go about finding it?

Even though the fans check out, is there any way it could still be that? If yes, how to test ?

Thanks for helping -- This is starting to piss me off! I've got one week before I have an appt to take it to a shop.
 

OlyTDI

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If I disconnect one fan at a time, and run the engine and turn on the AC, will the system fully activate minus that fan? In other words, can I isolate one fan at a time while simultaneously running the rest of the system?

I'm still thinking that this is some sort of startup overload which I'd like to isolate. Can't use a clamp meter as the fuse blows instantaneously when it does blow and only on AC startup -- not after it's running.
 
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