'04 jetta fuse box above battery

xmegxcalix

I have a 2004 jetta that has a short causing the fuse box above the battery to short out, it has happened twice now and we replaced the fuse and fuse box but we don't know what the underlying issue is. Has anybody had this issue before? The check engine light is also on and gives no code but says cooling system. Are these issues connected?

bpeebles

Your specific problem could be anything.

I believe you are really referring to the power-distribution-unit (PDU) mounted on top of the battery. The fusebox is INSIDE the vehicle located on the side of the dashboard when the drivers-door is open.

However, It is not unusual for some of the screw-down connections within that PDU can corrode. a poor-connection can build-up enough heat to melt things.

THIS IS NOT A "SHORT" - it is simply a poor connection. Heat is generated when resistance goes up.... basic electricity.

To prevent this kind of thing from happening, the screw-down connectors should be regularly snugged-up and perhaps even removed and cleaned.

I personally check mine about once a year... along with snowscreen-cleaning and other maintenance items.

xmegxcalix

It doesn't seem to be coming from the connections on the metal fuses. It seems to be coming from the wire going into the box. It has also melted. This has happened twice now in less than a year.

bpeebles

I have troubleshot and fixed many of these such problems on several vehicles. The answer is the same as I described above.... Poor connection = heat

It is ENTIRELY possible that the wire has poor connection to its termination. (rather than the termination to its screw-down)

This is simple to diagnose. Use voltmeter across the connection in question whilst there is current passing thru it. If you measure any more than say 30mV... then you have isolated the bad connection.

(A good connection should have 0volts across it with full-rated current passing thru it.)

The cause of this is that over time, the envrionment under the hood of a car is corrosive to all the exposed electrical connections. Even the slightest winter roadsalt into a connection can become an electrolite. Dissimmilar metals with an electrolite between them causes copper to to turn green (Copper-Sulfate). This green stuff is NONconductive to electricty.

You can continue to replace parts... or FIX the problem... your choice. Anyone knowledgable with basic electricty should be able to pinpoint the problem and effect a long-lasting fix.

xmegxcalix

Thanks for the info. I did end up taking my car to the VW dealership to be fixed. The alternator harness was giving off too much power and melting the fuse box. I had it replaced and the car works fine now.

superjetta

I also have a 04 Jetta and Im having problem intalling the box that goes right above the battery. My old one started failing and where one of the fuses go it started melting. So I bought a new one but once i install it my car has no problem. Im putting it identically how the other one was and nothing. I exchanged the part at the store but still nothing. If i put the old one back on it will work perfectly fine. Im not sure if i have to do something extra once i install it.

Need help please!!!!

jkmarley

How much did the dealership charge you?! I'm having the same problem.

superjetta

I actually installed it myself, all i had to do was remove some metal plates that are on the old part, the new part does not come with them. Where you screw the extension there are several little aluminum plates and just swap them to the new box

bpeebles

This looks like a GREAT time to remind everyone with a MKIV VW to keep those connections clean and tight!! Lest you will get melted parts and possibly a fire.

There are not a lot of things on the MKIV to PM.... but this is one of them.

PM = Preventive Maintaince

Oh -- and to answer your question.... use a VOLTMETER to determine the problem and then fix it. This is simply a bunch of fuses.... how hard is it to make sure voltage is on both sides of each one?

Dont forget that your radio may go into "SAFE" mode when you disconnect the battery unless you use a back-up power source.

cjmccoy

How do I go about changing my PDU? I've located a replacement and it looks like it would be fairly simple to replace it myself.

jkmarley

The box itself is easy to replace, but I ordered mine and they sent it with the incorrect fuses. The fuse under the thick black wire/connector if u have a 1.8L Turbo should have a 150amp fuse. Dorman sent me a PDU with a 110amp fuse which ended up melting the box again...and the wire....which cost me $600 at the dealership to fix. Ugh!!!!!!!!

xmegxcalix

I think we paid between $400-500 to replace the alternator harness and one fuse. If you have to replace any fuses or the fuse box buy them online, its way cheaper. I don't know about the alternator harness though.

xmegxcalix

It is very easy to replace but with ours there was an underlying issue causing the problem in the first place so I would recommend getting it checked out. If any of your Jettas are over 100,000 miles and you haven't replaced the timing belt I suggest doing it. We replaced the clutch at 106,000 miles and two weeks later the timing belt went out and blew the engine. No more Jetta for me. Good luck to you all but I will never own a Jetta again. Too many electrical issues. It should be recalled.

bpeebles

Let me understand this - You did NOT replace the timing-belt at the recommended interval and it broke.... hence you blame VW?

I would argue that ANY vehicle which you ignore the recommended major preventive maintenance could end up the same way. Hence, save yourself some grief and prepare to blame your next car now. - LOL

Also, a "recall" (by federal law) is solely for proven SAFETY issues. Perhaps you are suggesting a TSB (Technical Service Bulletin) should be created?

xmegxcalix

Yeah I learned from my mistake about the timing belt hence the warning for others. I wasn't blaming VW actually I blame my mechanic for not replacing it while he had the engine out. It wouldve cost about $300-400 more to have it done right after I just spent $400 so we were going to wait to get some more money together. The recall I think should be for the fuses and wires that keep melting because yes they can be a safety issue.