:scratchchin: Iv been thinking about this 100A fuse problem

[stu 9thgate]

After the trouble I had this weekend changing the 100A alternator fuse . I think I may has sussed a rather obvious alteration to make .

As I am sure you all know the alternator fuse is located underneath the car around the mid section next to the starter motor. If the fuse blows you have a limited time to ramp it up and change the fuse before the battery dies.

What if I was to remove the fuse altogether, crimp and heat-shrink the cables at this point. Then cut the wire in the engine bay behind the alternator and re-locate the fuse there!

Has any one done this mod before?. or mabey someone knows a good reason why the fuse is located in such a hard to reach location that it is, and im being daft.

If it’s because of the heat under the bonnet then a heat proof casing could easily be applied to the fuse holder. You may say that it probably wouldn’t be necessary , but if you are driving long distance (i.e. France) and it blows . Even if you are carrying a spare fuse you probably won’t be carrying a spare set of ramps too!.

In my last posted topic on this subject one guy even said he changes the fuse every service and after 12 months use the fuse was showing signs of stress.

Sorry if this has been coverd before , iv only been a chim owner 4 months.

What do you think people ?

Edited by stu 9thgate on Wednesday 18th October 21:19

[theaxe]

I've thought of doing this but always assumed that it'd be a space issue.

I belive that some people have just removed the fuse altogether. Personally I think that the main reason that they fail is corrosion. Mine was very badly pitted when I changed it.

[GreenV8S]

stu 9thgate said:

What if I was to remove the fuse altogether, crimp and heat-shrink the cables at this point.

I would say you're on the right lines, but stop there and don't bother with the rest of it. The 100A fuse seems to be a recurring source of problems, for no benefit at all that I can see. My V8S doesn't have one, and I can see no point at all to them.

[shorty123]

Mine went this summer, and owing to the inconvinence of where the car finally ran out of battery juice and died, and the fact me and my missus could have been killed rescuing the car from un uphill blind stretch of dual carriageway, i decided to do away with the fuse, bolt the cables together and seal the join up with potting compound.

problem solved. If your worried (as you suggest) connect some tails on either side of the fuse connectors, extend them up into the engine bay, fix on the wing or bulkhead and fit a more robust fuse or breaker.

Edited by shorty123 on Thursday 19th October 00:40

[stu 9thgate]

being a electrician i would hope that i would know the true value of this big fat nasty fuse. In a house i would say i have never known a 100A fuse to blow in 12 years experiance. But auto electrics are not my field, can some one shed some light on how important it is?. or not in this case. re-locating to the engin bay is as far as i can see a easy opption . are there any car sparks about on this forum who can help?

[shpub]

The reason for it is to prevent the alternator shorting out the battery. There are some failure modes that can lead to direct shorts and in this case it effectively means shorting out the battery. In extreme cases the battery can go bang. In others the cabling melts and starts a fire. It is pretty rare but that fuse can be a car saver. As for fuse problems.... never had any. Like many things, you only hear about the times when it goes wrong, not when it doesn't.

Edited by shpub on Thursday 19th October 08:50

[GreenV8S]

shpub said:

The reason for it is to prevent the alternator shorting out the battery. There are some failure modes that can lead to direct shorts and in this case it effectively means shorting out the battery. In extreme cases the battery can go bang. In others the cabling melts and starts a fire. It is pretty rare but that fuse can be a car saver.

That's the only possible excuse I can see for it, but I've never heard of an alternator failing like that. Even if the rectifier pack goes, it just gently discharges through the coils. I think it would need wiring damage inside the alternator combined with an electronic failure to produce a short, and if you're concerned about that then what do you do about the possibility of external wiring faults, which are probably more likely and not protected by the 100A fuse.

[Cider Andy]

stu 9thgate said:

being a electrician i would hope that i would know the true value of this big fat nasty fuse. In a house i would say i have never known a 100A fuse to blow in 12 years experiance. But auto electrics are not my field, can some one shed some light on how important it is?. or not in this case. re-locating to the engin bay is as far as i can see a easy opption . are there any car sparks about on this forum who can help?

The difference between your house and your car is the voltage. Take a 60W headlamp in your car. This will draw a steady 5A current. A 60W lamp in your house will draw just a 0.27A current. So, equipment in your car of the same power as that in your house needs almost twenty times the current to operate, meaning that, in power terms the 100A fuse in the car is equivalent to a 5A fuse in the house. Put simply, the 100A car fuse is not as 'big' as the 100A house fuse.

shpub said:

The reason for it is to prevent the alternator shorting out the battery. There are some failure modes that can lead to direct shorts and in this case it effectively means shorting out the battery. In extreme cases the battery can go bang. In others the cabling melts and starts a fire. It is pretty rare but that fuse can be a car saver. As for fuse problems.... never had any. Like many things, you only hear about the times when it goes wrong, not when it doesn't.

Maybe. But a faulty starter motor could cause the same problem, but there's no 600A fuse on its circuit. And we know from this forum that not all cars are fitted with it. No other make of car I've owned has had such a fuse.

Anyone concerned about retaining this fuse could mount it somehwere more accessible: this would be quite sensible. But when it fails on my car but it will be removed.

[TVR keith]

So has anyone actually moved this fuse or does anyone know of a reason why it should not be?
Mine has never caused any problem, but I'd rather sort this out in the comfort of my garage where I can get under the car, rather than be stuck waiting for the RAC at the side of the road, possibly in a dangerous position.

[victormeldrew]

As a cautionary note, if you removed the fuse and your car subsequently caught fire, don't expect too much from your insurers!

[hugepiece]

my old chim didn't have one at all, I know cos I spent hours and hours searching for it when the alternator packed up. It actually damaged the wiring when it went and I had to have the circuit re-wired - so I wish one was fitted. I recently saw a post on the cerb forum where a guy relocated the fuse to the top of the engine bay and replaced with a heavy duty car audio fuse and fuse holder, the post is :

www.pistonheads.com/gassing/topic.asp?t=309874&f=6&h=0

well worth a look I suppose if not just for peace of mind.....

[r666 tus]

Has anyone ever seen a fuse like this on any other make
of car ? I know I havent.Had loads of fords using same
types of alternator and they all have the positve cable
from the battery going direct to the solenoid on the alt.
When my 100 amp fuse went on the Tuscan there was nothing
wrong with the alternator the fuse had just deteriorated
and snapped. Hence I have removed mine from the Chim.

Col

[DAVID BEER]

When mine went yet again, i made a short wire link with soldered 100 fuse from the starter and bolted it to the alternator wire. So it can not break anymore and has less crimped connections and one less bolted connection. I do not see an alternator either drawing or producing enough to blow it, so it was only there to protect against the cable shorting to the chassis, or more likely the engines sharp bits !
I noticed my voltage reading lower for a couple of days before it finally went, so was most likely the connections arcing and then overheating the fuse. I would not sleep at night without a fuse there ! In fact if i was running a cable anywhere, i would always include a fuse at the origin. I know the true origin of the wire is the battery, but we know we can not have a fuse there !

[shpub]

I found a fusible link built into the LS1 corvette wiring loom in the big red cable that connects the alternator output to the battery/solenoid. At first glance looked like a single piece of wire but one end was marked fusible link. It is more common than you think and simply protects the alternator and associated wiring.

[Cider Andy]

shpub said:

I found a fusible link built into the LS1 corvette wiring loom...

Yes, I saw a similar factory fitted device on a 1973 Cortina, except it was connected to the battery post, protecting all circuits except the alternator and starter motor. It even had 'fusible link' printed on it but no current rating.

Presumably, as it cost time and money to start installing this fuse, TVR had a good reason. It's just that it seems to cause more problems than it solves.

[bigdods]

Just had mine changed during a service as a precaution. Never had it touched before but after all the horror stories decided to get it done. Cost virtually nothing , changed while they had it up on the ramps. Original fuse 9 years old still in good condition but changed it anyway.

[stu 9thgate]

what is the cable size? , looks like 16mm to me, is it copper?

[shpub]

Cider Andy said:

Presumably, as it cost time and money to start installing this fuse, TVR had a good reason. It's just that it seems to cause more problems than it solves.

There are many many cars out there where the fuse has not caused a problem. Including the 11 TVRs that I have had. BTW there doesn't seem to be the same comments about the other fuses. Why not remove them after all they can also fail and cause problems. Why not simply replace them with nails? That seems to be a pretty stupid thing to do yet the 100AMP fuse falls into the same camp. It protects the car. And yes like any fuse it can fail and reduce reliability slightly.

It's like the "all TVR's overheat" myth. Yes they can have cooling problems and if you look here it is almost like every car is affected. The reality is far different. The majority don't. Those that do usually have some kind of fault. Maybe if people started regularly posting my car didn't overheat or blow its fuse today, it would give a more accurate picture. It would be very tedious though...