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[Dan1005]

So as the title says I have spent all day calling up for fuses to put one back in the engine management system, and everywhere here says that they are non existent,, the highest you can get is a 30amp one...

Pretty crazy me thinks.. 

[Welung666]

As I said in your other post I have an 80amp engine bay fuse here.

[Dan1005]

Thanks Welung666.. I thought I sent you a PM about it this morning?? maybe I missed you,, ill resend it

[Marks DTM Calib]

They are described as a 'Maxi' fuse.

Easy enough to find

[jereboam]

Pardon my ignorance, but 80A seems rather large for a fuse.  What is it protecting? 

[Marks DTM Calib]

Pardon my ignorance, but 80A seems rather large for a fuse.  What is it protecting? 

Post 1997.5 model year, the Omega gained a supply distribution setup housed in a small box above the battery pos terminal.

This has 3 or 4 fuses in that effectively protect the major supply circuits to the cabin, engine etc....after these fuses, they are further fused on the tributary circuits.

Hence they are big buggres

[jereboam]

Pardon my ignorance, but 80A seems rather large for a fuse.  What is it protecting? 

Post 1997.5 model year, the Omega gained a supply distribution setup housed in a small box above the battery pos terminal.

This has 3 or 4 fuses in that effectively protect the major supply circuits to the cabin, engine etc....after these fuses, they are further fused on the tributary circuits.

Hence they are big buggres

Thanks for that.  But if the tributary circuit fuses haven't blown, surely the entire engine compartment is likely to be in flames by the time an 80A fuse blows?

[Marks DTM Calib]

Pardon my ignorance, but 80A seems rather large for a fuse.  What is it protecting? 

Post 1997.5 model year, the Omega gained a supply distribution setup housed in a small box above the battery pos terminal.

This has 3 or 4 fuses in that effectively protect the major supply circuits to the cabin, engine etc....after these fuses, they are further fused on the tributary circuits.

Hence they are big buggres

Thanks for that.  But if the tributary circuit fuses haven't blown, surely the entire engine compartment is likely to be in flames by the time an 80A fuse blows?

A fuse should be

As close to the source as possible e.g. the battery
Should be rated as a maximum to the limit of the downstream cable

So, after the fuse is stonking cable through to say the fuse box.....this is where the trib fuses are.....

And hence, the cable would not be in flames before it blew as its rated to 80A continuous current carrying capacity 

[Dan1005]

Also the cable would doubly not be in flames, because one of the fuse spots had a 30amp fuse slotted into it.. Here there is total denial of 80amp fuses being in existance (until I finally found some today)... so I think a smaller fuse than what is needed in it blew out..
Not 100% sure on that, so its going to a auto electrician tomorrow...

[jereboam]

Pardon my ignorance, but 80A seems rather large for a fuse.  What is it protecting? 

Post 1997.5 model year, the Omega gained a supply distribution setup housed in a small box above the battery pos terminal.

This has 3 or 4 fuses in that effectively protect the major supply circuits to the cabin, engine etc....after these fuses, they are further fused on the tributary circuits.

Hence they are big buggres

Thanks for that.  But if the tributary circuit fuses haven't blown, surely the entire engine compartment is likely to be in flames by the time an 80A fuse blows?

A fuse should be

As close to the source as possible e.g. the battery
Should be rated as a maximum to the limit of the downstream cable

So, after the fuse is stonking cable through to say the fuse box.....this is where the trib fuses are.....

And hence, the cable would not be in flames before it blew as its rated to 80A continuous current carrying capacity 

Thanks again for your patience, but I'm still not getting it.  Is it the case that the total of the outputs from the fuse box could under certain circumstances exceed 80A without any individual output exceeding its own rating?

If so, then the 80A fuse will blow without anything being wrong.  If not, then when will it blow?

I'm relying on A level physics learned 45 years ago, and I don't know nuffink about auto-electrics or electrical engineering.  Promise that's my last question.

[Marks DTM Calib]

Lets consider the following

Battery --(BIG CABLE)--- 80A fuse ---(Biggish Cable)---Fuse box.

So, the fuse box cant take more than say 80A via that feed.....

And once at the fuse box, further smaller fuses then protect the tributary installs.

It basic Kirchoffs current law
            

[Dan1005]

Can I ask a question...
if anyone who is looking at this topic has a 1998 Omega 3.0 V6... could they just check the fuse box on top of the battery that holds these 5 fuses.. and tell me if all have 80A fuses in... as this will eliminate my concern of a 30A fuse blowing after 800km of ownership of the vehicle...
Thanks