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Discussion Starter #1
Ok, its a pun. Sorry, this is my first post, bear with me. Just bought my 2001.5 used, and love it (looks like the model one above this!). Wanted brighter lights, got H7 SilverStars (are OK, shoulda got Philips) for low beams and PIAA H3 Ion Crystals for fogs. Wanted a cool, yellow import look like old Mercedees have. Used Rich's fog replacement, no prob. Worked fine.

One day later, the PIAA fogs blew their fuse. I replaced the fuse, they blew it again. I got the 55 watt ones, from an ebay seller (I know, I know). When I put the factory fogs back in, everything is fine. Asked an Advance Auto guy, he said up the fuse to 20 or 25. VW says bad idea. So, gurus, I know you're tired of answering newbie light-related questions, but humor me. I shelled out the $$$$ for the bulbs, and would like to be able to use 'em.
 

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The fog fuse is a 15A. That means a total power capability of 180W (less a tiny amount, because of the fog LED in the switch), and should be plenty of fuse if those are really 55W bulbs, and if there is nothing else wrong.

Perhaps PIAA underrates their power spec (and hopes no one checks), or you have a bad bulb (or two), or you have a short somewhere (unlikely, because the stock bulbs don't blow fuses), or someone wired up something else to the fog light circuit (thus increasing the total current draw for the circuit).

One possibility is a prior owner modified your vehicle for rear fog lights. The rear fog bulbs are 21W; if he wired both sides that would be 42W plus 110W for the PIAAs. That should be okay, but remember the PIAAs may be underrated. (To see if you have rear fogs, put on your parking brake, turn on your ignition, turn on your headlights, make sure your low beams are on and not the high beams, pull the headlight switch all the way out, then walk to the back of the car and see if any of the taillights are now as bright as the brake lights.

Another possibility is that your alternator is putting out more voltage than it should. Let's say the bulbs are rated at 55W at 12V. That means about 4.5 amps each. Okay, but an alternator generally puts out more than 12V, more like 13V or even 14V. Let's say it's 14V. Well, those "55W" bulbs are now going to be pulling more like 5.25 amps each. Now let's say your alternator (actually, the voltage regulator) is whacked, and your car is getting 16V. Well, that's bad for pretty much all the car's electronics, but those 55W bulbs are now going to be pulling 6 amps each or so. Add in the possibility of under-rated PIAA bulbs, and goodness ...

Now - that's getting a bit out there, and too scary. After all, your regular bulbs work fine.

If it were me, I'd wire up each PIAA bulb with an amp meter and see just how much current they are drawing. Just make sure you have an amp meter capable of measuring up to 10 amps. Do each bulb separately, and you should have someone help you by running the engine at a reasonable RPM - say 2500. Compare them to the current draw of the stock bulbs.

If the bulbs are drawing over 15 amps together, then your only choices are use something else, or replace the fuse with a bigger one. There is extra capacity in your wires. The VW engineers wouldn't put in wires that are "just big enough", so increasing the fuse to 20A isn't going to put you in immediate danger. But, me? I'd rather know what is going on, so I'd check the actual current draw of the bulbs.
 

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Discussion Starter #4
You da man, OakHill

I appreciate the extensive feedback a ton, and will get back to you asap with what's going on. I emailed some other people; would a dirty bulb or socket connection be a possible cause? Just wondering. This is the best car user discussion group I've ever seen, I've always heard VW owners are wicked smart!!!
 

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Re: You da man, OakHill

adamwilk said:
would a dirty bulb or socket connection be a possible cause?
If there were some conductive dirt or grease causing a short between the powered terminal and the ground terminal, yes that could cause a problem. Generally, dirty connections would tend to decrease the current flow, not increase it.

Also, if it were a problem with the socket connection, you would expect to see the OEM bulbs blowing fuses.

I'm betting that the PIAA's burn more juice than their 55W rating.
 

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Discussion Starter #7
OK, finally heard back from PIAA, wanted to wait for that before doing too much work. Here's their tech's reply:

We've heard of this. Our bulbs are actually slightly higher than the OE bulbs. If you do the math the 15amp fuse is big enough even for our bulbs but it still blows.

Why, nobody is sure yet.

Sorry for the vague answer.


John

PIAA Tech

I also emailed Daniel Stern, he said this:

PIAA = problems no matter how you slice it. Poorly-made crapola priced high to make you think you're getting "professional grade" bulbs.

So basically I'm hosed. Don't buy PIAA lights, i'm out 50 bucks!!! I think you're right, Barnacle-Billy and OakHill.

Appreciate the input, amigos.
:beer: :beer:
 

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PIAA Tech said:
If you do the math the 15amp fuse is big enough even for our bulbs but it still blows.
Why, nobody is sure yet.
Their math must suffer from Garbage In -> Garbage Out. The following link would help them understand "why": http://www.google.com/search?q=Ohm's+Law

Adam, you could still try a 20A fuse. VW is going to say "bad idea" because it is the safe answer. But your wires should be okay.
 
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