Jetta and Golf Electrical Problems
 

HI:

I'm new around here, I have two a golf MK4 2000 and a Jetta 2005 both with the same problem, "THE MAIN FUSE BOX MELTS OUT SOME FUSES".

Here is the explanation:

For the Golf: always melt the the first green fuse (cooling fans fuse) from left to right, I already take it to the pros and they say that there is to much resistance on that fuse bot nothing more they add a cable there to dissipate the resistance.

For the Jetta: always melt the the first metal fuse from the left to the right the one that came directly from the generator/alternator, it is just happens yesterday and actually I can't believe that it is just happening this to the jetta too.

Note: in both cases the fuses weren't blow away, they just melt the plastic that surround it and the plastic of the main fuse box that's holds them.

PLEASE IF SOME ONE HAVE ANY IDEA OF WHAT IS REALLY GOING ONE HERE JUST LET ME KNOW. I KNOW THAT IT IS ANOTHER POST ABOUT THIS BUT I DON'T KNOW IF THERE IS ANY UPDATE.



Appreciate

when the holder melts usually the plastic becomes conductive, the fuse in time will not seat properly and its leads become hi resistant and overheat, cut wires around the back of the fuse block and put in an inline holder

afarfalla: thanks for your responce I have this for you.

Actually I found the problem, the problem is the cable that run from the alternator to the first metallic fuse from the left to the right (110amps or generator fuse) when you are LOOKING the main fuse box right in front of you.

This cable, with time is affected for the heat and become less conductive, this reason, apparently, is the factor that cause this specific overheat that melt the black plastic of the main fuse box and some times the first green fuse to.

Meticulously, with an digital voltmeter and the engine running, I take the volts measures with the old cable and the new one from end to end, With the old cable from the alternator to the first metallic fuse it measures 13.27 volts and with the new cable from the alternator to the first metallic fuse was 14.08 volts. ("NOTE: The maximum voltage drop in an automotive circuit, as recommended by the Society of Automotive Engineers (SAE), is as follows: 0 Volts for small wire connections;O. 1 Volts for high current connections; 0.2 Volts for high current cables; and 0.3 Volts for switch or solenoid contacts. On longer wires or cables, the drop may be slightly higher. In any case, a voltage drop of more than 1.0 Volt usually indicates a problem) from the Bentley service manual.

I am sure that this droppings in the voltage are highly marked in some other cases when the destruction of the fuse box and the fuses are really more evident, since I already got this problem in the my Golf (2002 MK4 and got the main fuse box severely damage) I was just waiting to happened to the jetta (2004 from Mexico) too, and already see it in so many other VW owners at other forums.

As you might know "A voltage drop test is generally more accurate than a simple resistance check because the resistances involved are often too small to measure with most ohmmeters. For example, a resistance as small as 0.02 ohms would result in a 3 Volt drop in a typical 150amp starter circuit (150 amps x 0.02 ohms =3 volts)" from the Bentley service manual.

For that reason I dice to use the volts so: "Keep in mind that voltage with the key on and voltage with the engine running are not the same. With the ignition on and the engine off (battery voltage), voltage should be approximately 12.6 volts. With the engine running (charging voltage), voltage should be approximately 14.0 volts. Measure voltage at the battery with the ignition on and then with the engine running to get exact measurements" from the Bentley service manual.

So, as you can see a damage cable can cause sufficient resistance to drop the voltage, and then melt the fuse box, but not enough to fracture it, also this cable got three intermediate plugs and if I am not wrong the first one, is for the alternator, the second is for the A/C compressor, and the third one is for something else below the batterie, so this means that this is a high current cable, so no differences more than 0.2 volts and mine got 0.8 volts.

To conclude: With the engine running (charging voltage), you must got ≈ 14.00 volts or ≈ 14.08 volts at two specifics points; at the alternator and in the main fuse box at the first metallic fuse nut where it enters the main fuse box (110 amps generator fuse), if the difference between this two measures is more than 0.2 as corresponding to the high current cables according to SAE then you must replace the alternator to battery cable or harness whatever you wish to name it as I do.

PLEASE IF SOME ONE HAVE MORE INFORMATION, ABOUT THIS ISSUE JUST WRITE IT DOWN

THANKS APPRECIATE IT………..

Here are the photos:

http://picasaweb.google.com/ELGuerra...useBoxProblem#

Hi,

Have you resolved this issue with your melted fuse? Mine looked fine and no indication that the cable or the fuse box running hot. However, I do have a charging issue though. The battery drained around 4-5 days with normal driving. The Interstate battery and a Bosch rebuilt alternator is about 2 months old. I had both the battery and alternator removed and checked by an alternator shop without any issues.

I've cleaned & tightened every connections between the alternator and battery and the ground cable.

The next step is to buy a new cable between the alternator to the fuse box on-top of the battery to the first fuse (stand in front of the car).

All else fails, I will drive it in a Kia dealership and trade for an used Optima.

Please let me know.

Thanks,

Jay
2003 Jetta VR6

Jat007

The answer is yes the first fuse in the fuse box, never melt againg, the fuse box looks very clear since y change the cable that goes from the alternator to the first fuse, It works pefecthly....