The 'Big Fuse' and associated problems

[Nicholas Blair]

Does it generally go 'bang' ? Heard a noise at the weekend but didn't give it a second thought.

Tried to start car tonight and noticed rev/speedo don't work.

Finally started her after charging up battery for an hour. Nipped out for a quick spin and the battery light came on and car died in the fast lane .

Coasted into layby,luckily towed home by neighbour.

What a b******d!

Nick

Edited by Nicholas Blair on Wednesday 5th March 21:24

[brogenville]

The usual problem with the big fuse is a general degradation over time which leads to voltage fluctuations that manifest as such symptoms as a fluctuating speedo. I suppose the eventual result is that the fuse will go pop, but lickely not before you would have experienced some of the usual big fuse problems. Its easy enough to have a look at it, so in fairness you may as well start by checking the big fuse anyway. I suspect your alternator may be on its way out though.

[Nicholas Blair]

brogenville said:

The usual problem with the big fuse is a general degradation over time which leads to voltage fluctuations that manifest as such symptoms as a fluctuating speedo. I suppose the eventual result is that the fuse will go pop, but lickely not before you would have experienced some of the usual big fuse problems. Its easy enough to have a look at it, so in fairness you may as well start by checking the big fuse anyway. I suspect your alternator may be on its way out though.

Thnaks Brogenville - thoght the alternator had something to do with it.

I managed to find a thread on it but seems a bit of a s**t job to sort out.

Garage, here we come.

Cheers

Nick

[350Matt]

Well worth changing the std 'big' fuse for a maxi fuse ( see vehicle wiring products website)these fit the std holder but are more mechanically robust so less likely to crack under vibration etc

Matt

[gbbird]

Nick,

I think the big fuse and the associated housing was completely changed about 18 months ago on that car, so i would be suprised if it was that. Worth checking though - some people change their big fuses every year, as the consequences of a 50p fuse going are disabling. It once went on me, but as posted earlier in this thread, i did have the symptoms for a good few weeks beforehand, which i stupidly ignored.

Hope it gets sorted soon

g

[Nicholas Blair]

gbbird said:

Nick,

I think the big fuse and the associated housing was completely changed about 18 months ago on that car, so i would be suprised if it was that. Worth checking though - some people change their big fuses every year, as the consequences of a 50p fuse going are disabling. It once went on me, but as posted earlier in this thread, i did have the symptoms for a good few weeks beforehand, which i stupidly ignored.

Hope it gets sorted soon

g

Thnaks greg

I was meant to off to Ireland today, alternative transport on call!

Cheers

Nick

[thegreengoblet]

350Matt said:

Well worth changing the std 'big' fuse for a maxi fuse ( see vehicle wiring products website)these fit the std holder but are more mechanically robust so less likely to crack under vibration etc

Matt

I'm with Matt on this one.
Mines been done and it's a lot meatier than the std ones, so I have a lot more faith
in it lasting. Check out Steve Heaths website.

[optimax sniffer]

Nicholas Blair said:

I managed to find a thread on it but seems a bit of a s**t job to sort out.

Garage, here we come.

Cheers

Nick

Did mine last year on my 4.5. Drop me an email ([e-mail]) if you want and I will send you my phone number, if you get stuck

[Nicholas Blair]

All fixed - can't believe a little piece of metal like that caused so many problems. Took me a good couple of hours to sort it all out.

Anyway, kit in the car just incase it happens again.

Thanks to all.

Nick

[thegreengoblet]

Nice and simple fix.

Well worth looking into those midi fuses - they are so much more substantial. The metal ones - and some are worse than others - flex when you do the nuts up after replacing the fuse. So not a good start to the life of the fuse.

[TVR Paul]

Please excuse my ignorance.. but what is the BIG FUSE and what symptoms can it cause when it starts to degrade?

Paul

[SlvrCrb]

TVR Paul said:

Please excuse my ignorance.. but what is the BIG FUSE and what symptoms can it cause when it starts to degrade?

Paul

It's a 100amp fuse located between the alternator and the battery. Main symptom of it going is the rev counter bouncing around all over the place. It's not a big job to replace but fiddly if you have sausages for fingers.

hth

[Gazzab]

You may also notice the radio reception getting worse (it is possible!) and the car getting harder to start.

[Nefarious]

SlvrCrb said:

It's not a big job to replace but fiddly if you have sausages for fingers.

A 1/4" ratchet with both extention bars on is your best friend.

If you've got a magnetic pick-up tool (or any other kind of magnet for that matter), stick it to the extention bar, so you don't drop the nuts.

If you do have fingers like a pack of the butcher's finest, refit with wing-nuts or those gnurled-top nuts you get on the back of speakers/computers.

[thegreengoblet]

And don't forget to disconnect your +ve terminal of your battery before attempting to change the fuse.

[Scrooloose]

Or you could just bypass it.....

[Gazzab]

thegreengoblet said:

And don't forget to disconnect your +ve terminal of your battery before attempting to change the fuse.

Nah - just put lx tape on the socket and bar.

[TVR Paul]

Thanks for the info dudes.

Paul.

[Nicholas Blair]

Big Fuse went again the other day. I'm going to replace the battery anyway and move the bloody fuse, upgrading to the Steve Heath sturdier one I saw on his website - Anyone reckon my alternator is perhaps on the way out for this to repeat only 4 weeks after replacing the last fuse or signs of other electrical gremlins?

All suggestions gladly taken on board.

Cheers

Nick

Edited by Nicholas Blair on Monday 26th May 10:44

[arebrec]

big fuse on the cerb has gone twice in a year.

first time there were a few sympotms, lights flicking on and off battery light coming on intermittently and car feeling like it was gonna stall, this got gradually worse over a period of a few hrs then car just stopped. Battery power was low and was thought to be alternator or battery problem, was charged but then after a 5 min drive went again, as soon as the big fuse was changed the car sprung into life again

second time, had just come back from a long run, stopped car, then when tried to start again it just wouldn't. don't really recall any symptoms that time, but the big fuse was in a bit of a state, changed and all seemed ok.

still not sure if there is an underlying problem why the big fuse has gone or it was just because they were not up to the job, they were only thin cheap ones, box was also a bit knackered and may have been letting in water?!?

Have just ordered and received steve Heaths big midi fuse and a new box