I had a weird thing when I left the car at the airport at the weekend - the brake lights wouldn't turn off! I didn't have time to do anything about it, and of course when I got back the battery was flat. After a 3 hour wait (!!!!) for the AA man, he finally got us going.

 

Turns out that the distribution board connected to the battery was all gunked up, so the alternator wasn't getting any charge to the battery. He cleaned it up a bit which was enough to get us home. The brake lights apparently were a red (hehe) herring - apparently they're controlled by a relay which gets stuck open when the charge is too low (dumb design if you ask me!!). 

 

Anyway is it simple job to change the distribution board, or should I leave it to the experts? And where would I get one from? I tried gsf/eurocarparts but couldn't find anything.

 

Cheers!

I had a simular issue just unboltthe alternator from the distro board and connect it to the live battery terminal issue solved

To this day I can't figure out why you would fuse the alternator :/

I had a simular issue just unboltthe alternator from the distro board and connect it to the live battery terminal issue solved

To this day I can't figure out why you would fuse the alternator :/

 

Because its a high load wire running through the engine bay connected directly to the battery, If that wire shorts out against an earth its going to do a lot of damage before it melts to the point of disconnecting.

Could have unplugged the rear lights? Not much use to you now I admit

Sent from my C6603 using Tapatalk 4

It is a common misconception that fuses are there to protect the load. 

The fuse is there to protect the wiring. Without a fuse in place, damage to the wiring can cause a fire.

 

Of course, a fuse and cable correctly chosen can also protect the load against gross overload such as a short, however, when feeding multiple loads it is necessary to use a larger cable and fuse and in that case a local fuse must be placed in the load. That is why there is a fuse inside your radio to protect its internal wiring.

 

Never run a cable from a battery without a fuse at the battery end to protects the cable - and that includes high power amplifiers in the boot and the cable that connects to the alternator.

 

Could have unplugged the rear lights? Not much use to you now I admit

Sent from my C6603 using Tapatalk 4

 

Tricky to unplug the 3rd light (rear window)? Anyway yes too late!

It is a common misconception that fuses are there to protect the load. 

The fuse is there to protect the wiring. Without a fuse in place, damage to the wiring can cause a fire.

 

Of course, a fuse and cable correctly chosen can also protect the load against gross overload such as a short, however, when feeding multiple loads it is necessary to use a larger cable and fuse and in that case a local fuse must be placed in the load. That is why there is a fuse inside your radio to protect its internal wiring.

 

Never run a cable from a battery without a fuse at the battery end to protects the cable - and that includes high power amplifiers in the boot and the cable that connects to the alternator.

 

Hmm, I do have an amp. Then again it's been there for about 10 years now and I'm pretty sure it was fused when I put it in ... (I find it hard to remember last week these days let alone 10 years ago!!)

Because its a high load wire running through the engine bay connected directly to the battery, If that wire shorts out against an earth its going to do a lot of damage before it melts to the point of disconnecting.

If that were the case why is there not a fuse at both ends of the alternator cable? don't get me wrong I understand. The concept of it for example the high power amplifiers see below

That's 3500watts rms 2 runs of zero gauge front to the back battery fused at both ends for safety but fusing the alt wire still won't protect nuggets from themselves

In the case of the amplifier, it is correct to fuse at both ends but with different size fuses. The one at the battery end is protecting the cable(s) from a short to ground. The fuse at the amp end will be smaller as it needs to protect the amp internal wiring from an internal fault. This should be a faster fuse too unless it is much smaller than main supply fuse at the battery end.

 

I don't know why car alternators don't have a discreet fuse at the alternator end. It may be they are relying on a thermal link in the coils - or perhaps that is why we see diode failure so often! Diodes will always fail before a slow fuse operates.

 

You want the fuse as close to the battery as possible. If at any point the wiring goes to ground as a dead short the fuse will blow disconnecting the battery, the rest of the wire is then dead. The only part that would remain live is the feed to the fuse from the battery which in the case of the alternator is a small link wire from the positive terminal clamp to the battery top fuse box. A fuse at the alternator end would be pointless as the source is fused anyhow, and the fuse is the weakest link so no matter where the short is on that wire it will blow.

You want the fuse as close to the battery as possible. If at any point the wiring goes to ground as a dead short the fuse will blow disconnecting the battery, the rest of the wire is then dead. The only part that would remain live is the feed to the fuse from the battery which in the case of the alternator is a small link wire from the positive terminal clamp to the battery top fuse box. A fuse at the alternator end would be pointless as the source is fused anyhow, and the fuse is the weakest link so no matter where the short is on that wire it will blow.

I understand that is why it's there but in the real world the chances of that happening are slim to none. Even if there were to be an accident and the front end cave in there is just as much of a chance that the distro board will be broken causing a short to the battery as the same with the cable from the alternator

I know it's not a skoda but on my rover there are no fuses on the battery.

 

In the interest of safety and knowing how us brits have trouble with wiring, I have installed a circuit breaker style fuse on the battery, they are cheaper than replacing large fuses and when they pop you can fix the fault and flip the switch again instead of trying to find a new fuse.

 

I guess my point is, buy a circuit breaker of the correct flavour and install that inline with your alternator wire.

 

http://www.ebay.co.uk/itm/250A-12V-DC-CIRCUIT-BREAKER-REPLACE-CAR-FUSE-250-AMP-12VDC-CAR-AMP-POWER-WIRING-/271289246205?pt=Car_Audio_Video&hash=item3f2a1961fd