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Fuse box Replacement


AidanT
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New mini-project started today to replace and upgrade my fuse box. Why? well to start with the three glass fuses rated @ 35A each doesn't really do much and there is a certain "fizzing" noise coming from mine that is slightly concerning.

 

Anyway I have taken out the passenger glove box, and pulled out the fuse box from the bulk head.

 

As a test, I thought, before I do anything I will test the circuits to the positive battery connection as I believe that one fuse is for permanent live, one for ignition live and the final one for the light master switch live

 

When I tested though all the fuses show 0 ohms (no resistance) when making a circuit to the positive battery lead (battery removed)

 

Is this right?  All the electrics have been working correctly as far as I am aware.

 

 

Aidan

 

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Aiden,

 

here is an excellent wiring diagram, in colour, that I use. It's for a mk3, don't know how different a mk1 would be? My fuse box comes out from the bulkhead into the engine bay, that's one difference, but still 3 fuses. Note that the head lights have NO fuse and all the current for them goes through the light switch! A good reason to add fuses and relays.

 

http://triumphspitfire.com/images/wiring/GT6MkIIIwiring.jpg

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Thanks both. I really don't understand the test results but hey everything seemed to work as and when it should so im not going to worry 

 

Anyway so Next steps

 

The soon to be replaced

 

post-170-0-18026700-1495466892_thumb.jpg

 

Pictures of the wiring

 

post-170-0-75482100-1495467124_thumb.jpgpost-170-0-17124700-1495467133_thumb.jpgpost-170-0-35378800-1495467144_thumb.jpg

 

Labelled just in case!

 

post-170-0-38840000-1495466973_thumb.jpg

 

finally a look at the replacement -bigger in that i need to increase the size of the hole by 1 cm in length and 1 cm in height and make a separate hole for the loom but it gives me 10 fuses to play with

 

post-170-0-78921000-1495467339_thumb.jpgpost-170-0-69386700-1495467349_thumb.jpg

 

Aidan

 

 

 

 

 

 

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Thanks both. I really don't understand the test results but hey everything seemed to work as and when it should so im not going to worry 

 

Anyway so Next steps

 

The soon to be replaced

 

attachicon.gifIMAG0081.jpg

 

Pictures of the wiring

 

attachicon.gifIMAG0084.jpgattachicon.gifIMAG0083.jpgattachicon.gifIMAG0082.jpg

 

Labelled just in case!

 

attachicon.gifIMAG0086.jpg

 

finally a look at the replacement -bigger in that i need to increase the size of the hole by 1 cm in length and 1 cm in height and make a separate hole for the loom but it gives me 10 fuses to play with

 

attachicon.gifIMAG0088.jpgattachicon.gifIMAG0087.jpg

 

Aidan

Hi Aidan - Nice Fuse box . where did you buy it ?

Regards

Paul 

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Hi Paul. It was not the cheapest of fuse boxes but I purchased it from vehicle wiring products. Strangely they sell them cheaper through eBay than their own web site

 

 

EBay item no 262119144550

 

 

Aidan

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So the next step will be to measure the resistance of the circuits with all the car switches on.

 

I will list them tomorrow as the calculated amperages for the fuse set up as no one has ever seemed to have listed them on the tinterweb

 

Aidan

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Well I was able to measure some but not all. For the remainder I have used a bit of common sense and a few calculations based on what I do know. I do not accept any liability on the attached spread sheet but if it of use and if anyone thinks I'm wrong, I'm quite happy to update the document

 

Aidan

 

OK So it wont allow a spread sheet to be loaded so here's a CSV Paste - if you copy paste it to excel and delimit it by comma it should work - (Sorry going excel techy!)

 

voltage,,,,,A = V / R,,A = W / V,,,,
13.8,,,,,,,,,,,
,,,,OUTPUT,,,,,,,
INPUT,,,,,,,Measured,,,,
Fuse No:,From,Colour,,To,Colour,Calc Amps,Fuse A,V,W,R,Notes
,,,,,,,,,,,
3,Ign,White,a,Coil,Single White,4.6,10,13.8,,3,Calculated  - Standard 3 Ohm Coil
3,,,b,Gauges,Single White,0.1725,10,13.8,,80,80 ohms max resistance for the Fuel sender but I have 3 others
3,,,c,oil Warning L,Single White,0.1594,5,13.8,2.2,,The small bulbs are 2.2W
3,,,d,Stop L / Heater Fan,Twin Green,3.0435,10,13.8,42,,2 X 21w bulbs plus 5 for heater Fan
3,,,e,Indicators,Single Green,6.0870,15,13.8,84,,4 X 21w bulbs 15 A to be safe
,,,,,,,,,,,
2,Light Master,,a,Side & Tail L,Twin Red,6.0870,10,13.8,84,,4 X 21w bulbs 15 A to be safe
,,,,,,,,,,,
1,Perm Live,,a,Horn Relay,Double Purple,,10,13.8,,,Haynes Manual for a GT6
1,,,b,Main / Dip,Single Purple,9.4203,15,13.8,130,,2 X 65W  at main beam
1,,,c,Interior L,Single Purple,,5,13.8,,,Cannot be a hign wattage  - only one bulb
1,,,d,Overdrive,L Brown,,10,13.8,,,Added in 2014
 

 

 

Hmm It was better on the preview!

 

Happy to send the spread sheet if anyone wants a copy. 

 

Aidan

 

Just thought  - PDF!

 

Fuses estimated Requirement.pdf

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So fuse box now fitted snuggly

 

post-170-0-20748900-1495899818_thumb.jpg

 

Everything re-wired I have put all outputs to the fused side and used buzz bars for the permanent and ignition input side

 

Here it is finished

 

post-170-0-16131300-1495899677_thumb.jpg

 

 

Now just one issue - no front side lights. Everything else is working perfectly so far.

 

Something for tomorrow

 

 

Aidan

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Anyone any thoughts why the front side lights are not working? Tail and number plates are fine and they are wired from the fuse box on two red cables both of which are on one spade!

 

Bit odd!

 

Aidan

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  • 2 months later...

Just a final update - All the fuses per the above table have not blown in 2k miles of travel in day and night conditions and a trip to France, so my estimates are possibly overstated. Still a lot less than the original 35 Amps though so I'm happy

 

Regards

 

Aidan

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  • 8 months later...

Dragging this back up as it was linked from the thread I started here 

Whilst I fully understand the reasons for the fuse sizing based on the actual load, in reality you just need to fuse for the wiring. (Though you are playing safe in most cases by fusing for the load) - at the end of the day, you want the fuse to be the fuse and not the wiring. 

Looking at the wiring behind the dash of mine, the smallest cable would probably be 1mm - so the standard fuse box having 17/35A fuses would make sense as 1mm will take a continuous 16.5A - and most of the cables look to be nearer 2 or even 3mm so can carry a lot more load. (Based on vehicle wiring products website)

But going back to the fuse box I have just looked at the pictures how you fitted it and it does look good.  I was wondering how you dealt with the big loom going through the bulkhead!

 

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In simple terms I cheated !  I cut a separate hole for the loom and grommet and the cut a narrow channel between that and the fuse box hole. The grommet butts up to the fuse box nicely sealing up the gap. This avoids having to take the loom out, putting it through a new hole and re-wiring up 

Aidan 

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A buzz bar is a way to connect one side of a fuse boxes fuses together. As an example if you need three circuits to be live from the ignition, you don't run three cables from the switch you just run one and connect the other two fuses together with what's called a buzz bar ( mainly described as this in household fuse boxes)

As for circuits, it depends on the car. My mk1 for instance has seven std circuits so that left me with three fuses free I could have doubled up on quite a few (two or more circuits on one fuse) but chose not to. I also fused things like the coil circuit which are not fused at all on the standard fuse box as it's fed from the live side of the fuses

Aidan 

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If I remember right I couldn't find a car fuse box that came with a busbar hence having to make one. The other option is to make a small hoop of wire with double connectors so they can be joined. Again I did not think that was the best solution 

Aidan

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