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2002 volkswagen golf fuse box
I have a 2001 VW Beetle which has a nasty habit of melting the above battery high voltage fuse box. I've replaced it three times already and replaced the alternator as well, but I'm at a complete loss as to what's causing the problem.
Apparently this is a known issue with VW's from that era, there's even a class action suit against VW that's still working its way through the courts.
Is there a real, permanent solution to this problem?
I have a 2005 Golf MKIV and it did this also. Lost a/c, fans, overheated. The B+ wire from the alternator to the battery appears to be too small a gauge. I went to a larger gauge wire and replaced the fuse block on top of the battery. It also appears that the contacts for the three green fuses are not to tight fitting. My wife's a/c went out again last week. I moved the fuse around in it's socket and the fans and a/c clutch would then go on and off. I pulled out the fuse to slightly warp the contacts for better contact and I got the ends of my finger blistered for my effort. There was also a black arc literally burnt into the fuse contact. So when you see a company marketing their fuse block as good as the original, you might want to question that. A very shabby condition for such a technologically advanced company. Just no conscience. ergo the TDIs of late, and this too. Very disappointing. This is the only problem we have had with this car in 11 years and 112,000 miles.
An overheated electrical connection has but one cause, resistance to electron flow. Find the cause of this and fix it. The test for this is voltage drop under load.
1) Repair first. Replace all the burned parts with new high quality units, including the wire to the alternator. All bolted connections are to be torqued to specification. Consider reinforcing crimped connections with solder. All connections are to be cleaned to bright metal. Stabilant 22 will be painted on the faces of the bolted connections. Ensure that the bolted connections are not subject to vibration that could loosen them over time. Consider adding tie downs for the wires near the fuse box if none exist. 2) Now test the circuit. This will determine if the electrical resistance is fixed or is still present. Using a high quality volt meter measure the voltage loss of the circuit from the battery side of the fuse to the alternator connection. During this test the engine will need to be running and the high power use vehicle electrical systems will be on, heater blower, headlight, rear window defrost, etc… This value needs to be less than 0.1 volts, but a high quality circuit will have less than 0.01 volts. If this value is low then repairs are complete, if not narrow the search by testing shorter sections of the circuit until the problem is located. 3) To ensure the repair over time test the circuit in the manner listed above as often as you like, as long as the voltage drop remains low the repairs are holding. If not test for and repair the connection with the elevated voltage drop.
The B+ wire is likely alright if you noticed it on time, but the problem is due to the drained battery and the bad connection around the fuse. If it was the wrong gauge or something, it wouldn't melt around the fuse but likely elsewhere or wouldn't provide enough current to cause any damage.
This happened to me on 2002 Beetle a week ago. After my alternator died, I, apparently, drove on battery till it died in turn and I had to be towed. Alternators are meant to maintain battery charge and not to charge a totally dead battery as it would draw a very high current that may damage the alternator and, yes, melt the fuse. I replaced the fuse box, sanded well all the contacts, replaced 110A fuse, and greased everything up while charging the removed battery by a dedicated battery charger. The ammeter on the charger was showing very high current for a first couple of hours.
While replacing $150 worth harness won't hurt, get a peace of mind and buy a battery charger to use next time alternator dies.