TVR CERBERA (4.5) - Removal of Big Fuse - What do I need?

[RobTuscS]

Hi all, I am looking at removing my 'big fuse' I note that some of you have moved it and updated with a better system, which seems ok, but very little in the way of exact products used.

However, I have spoken to Jools at Kits and Classics (Cerb Guru!) and he told me a few weeks ago that the big fuse can be removed completely. Has anyone done this? I have taken enough of his time and as such wanted to ask here.

If so, what size cable did you use? I think 300amp cable has been discussed, but if I was to go for 375amp would this be of benefit or hindrance. I understand cranking of most, if not all starters crank is 375amps.

What length of cable is required? +ve and -ve, and I am also going to replace the earths as well (battery to chassis), as my cranking isn't consistent and I feel there is a draw of power if that makes sense. My starter motor gear set is mashing into the flywheel chipping the teeth a little, although I now think my new solenoid is fried after 2 months and the starter now just sounds like a drill again! But I am hoping this will resolve the issue before I spend more money on that again.

Note I have also purchased a Starter motor shim from Peter Essling which I hope to receive next week.

Any help appreciated. Thanks all 😁

[FarmyardPants]

The easy option is to just open the fuse cover, remove the two bolts, remove the fuse and throw it away, bolt both cables onto the same post and close the fuse cover.

Edited by FarmyardPants on Thursday 20th January 21:32

[FarmyardPants]

Just to add that the big fuse plays no role during cranking, it is part of the charging circuit (between alternator and battery).

[RobTuscS]

Thanks, Farmyardpants.

The other issues I have had are speedo jumping, rpm like a spring (although a lot of cars do this) However I understand that the aforementioned is to do with the Big Fuse. I did replace this, but my starter started to pack up, and now the car refuses to start as I think I have damaged the solenoid by trying to get it started. Grrr!

I think I have a few issues causing this, hence the comment about the bad earth. But I am trying to get all the bits to renew all of the battery, starter and alternator cables for piece of mind as much as anything. I want to renew the earths that are easily replaceable as well.

So, if you know what cables I need it would be appreciated but anything upgraded would be even better.

Thanks.

[MattPlaneCrank]

FarmyardPants said:

Just to add that the big fuse plays no role during cranking, it is part of the charging circuit (between alternator and battery).

I replaced my big fuse with a more robust solution. I think the conclusion from the discussion on here was that the fuse protects the battery from a rectifier / voltage regulator failure that would cause the battery to over charge, over heat explode etc. Unlikely but nasty.

[Ice_blue_tvr]

RobTuscS said:

Thanks, Farmyardpants.

The other issues I have had are speedo jumping, rpm like a spring (although a lot of cars do this) However I understand that the aforementioned is to do with the Big Fuse. I did replace this, but my starter started to pack up, and now the car refuses to start as I think I have damaged the solenoid by trying to get it started. Grrr!

I think I have a few issues causing this, hence the comment about the bad earth. But I am trying to get all the bits to renew all of the battery, starter and alternator cables for piece of mind as much as anything. I want to renew the earths that are easily replaceable as well.

So, if you know what cables I need it would be appreciated but anything upgraded would be even better.

Thanks.

There are two issues where the tacho "jumps" from 0 every now and again or just fails to register revs. This is due to it receiving low voltage and likely down to the big fuse. When my big fuse failed I saw running voltage in the low 10v range (that's with a healthy battery, so probably down to the long cable runs and crap earth's). At a guess I'd imagine the tach cuts off at 10.5v, which would explain its intermittent nature when they fuse fails.

If the tacho is "bouncy" (usually more so the higher the revs) you can put this down to either the damping mechanism needing repair, or simply it being the character of the tach depending on the state of your wallet at the time

Bearing in mind, that's the tacho, not speedo as you mention?

The big fuse wiring (on mine at least) goes from starter to fuse to alternator. Iirc the alternator is something like 100-120amp, so for that I'd be inclined to use something like 4awg, which looks similar to the existing size. Replacing for fresh cable that hasn't suffered years of oxidisation may help on its own.

Someone more knowledgeable can confirm, but Iirc, original wiring for the starting circuit goes from battery to rear fuse box then back to starter? And an "upgrade" being to add in a relay/solenoid that uses the front to back power as the "signal" and then a short length from battery to starter. This would give a nice boost in amps to the starter and in general be a safer way.

I have some 0awg lying around and keep meaning to tidy up some of the cabling, but I think it's probably too thick for a lot of runs, so will use 4awg where needed.