Glass fuses

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new to all this

new to all this

Well-Known Member
Posts
243
Location
East Sussex
Hi

Following on from my broken wiper motor and today I noticed my brake lights aren’t working (probably never have I guess from state of brake switch) I have been going through my glass fuses.

I have seen a number of conversations about continuous amps and blowing amp limits but nothing so far to identify from back of fuse lid whether what I am putting in is correct or what I have in there is correct. For example, the left hand side lights say they are 2.5a on lid but there is currently quite an old 35A fuse and in the right it has a 20a.

some of the installed fuses have no values stamped either at ends or on any paper inside so I am a little lost.
Mine is a 1987 90.
Thanks!
 
When my son bought his Ninety every fuse was incorrect, we cleaned up the contacts and replaced all the fuses. I don't remember it being aggravation, isn't the rating on the fuse box lid?
 
Anaconda said:
When my son bought his Ninety every fuse was incorrect, we cleaned up the contacts and replaced all the fuses. I don't remember it being aggravation, isn't the rating on the fuse box lid?
Click to expand...
Yes looked simple to me as all fuses are rated on the lid however people on here and elsewhere have said that the fuse rating on the lid isn’t the blow rating of the fuse.

hopefully that’s wrong and I am making a lot more of this than needed. To my mind what’s the point of listing it on the fuse box lid otherwise… but that’s just me being logical.
 
The fuse ratings on the lid are correct for a standard truck. If other items have been added someone may have up them a bit, however if a load is greatly increased like large spot lamps they should be run from their own relay. Some do this for headlamps as well when using stronger bulbs.
A little while ago I had the job of rewiring glass fuse 90, the owner was having problems with wiper blowing the fuse so stuck in a big one. Next time it rained it was meltdown time.:eek: Only problem for the actual wipers was seizing spindle wheel rods, a drop of oil would have saved a lot.:rolleyes:
Fitting a later blade type box is possible.
 
Fuses are there to protect the wiring.
Too much current and you let the smoke out.
There are two types of fuse, quick-blow and slow-blow.
A quick blow will melt and go open circuit at the instant the current rating is exceeded, a slow blow will allow the circuit to draw more current for a short time before it blows.
If you have a 10A slow blow and a short, the 10A rated wires will heat up before the fuse blows, the quick blow won't allow the wires to heat up.
Motors take more current to start than to run so slow-blow fuses are the norm.

Typically the fuse and the wiring is rated above the normally expected current drain, ie a 10A fuse and 10A wire will be used to supply a 4 to 7 Amp circuit.
Use the correctly rated fuses, better still replace the fuse box with a modern unit that takes automotive blade fuses.

Amps x Volts = Watts.
Watts = Volt / Amps
Watts / Volts = Amps

Brake light bulb is 21W,so it takes 1.75A, so a 5A fuse would be appropriate.
A headlamp takes 4.6A (55W) so a 10A fuse would be right...
 
miktdish said:
Fuses are there to protect the wiring.
Too much current and you let the smoke out.
There are two types of fuse, quick-blow and slow-blow.
A quick blow will melt and go open circuit at the instant the current rating is exceeded, a slow blow will allow the circuit to draw more current for a short time before it blows.
If you have a 10A slow blow and a short, the 10A rated wires will heat up before the fuse blows, the quick blow won't allow the wires to heat up.
Motors take more current to start than to run so slow-blow fuses are the norm.

Typically the fuse and the wiring is rated above the normally expected current drain, ie a 10A fuse and 10A wire will be used to supply a 4 to 7 Amp circuit.
Use the correctly rated fuses, better still replace the fuse box with a modern unit that takes automotive blade fuses.

Amps x Volts = Watts.
Watts = Volt / Amps
Watts / Volts = Amps

Brake light bulb is 21W,so it takes 1.75A, so a 5A fuse would be appropriate.
A headlamp takes 4.6A (55W) so a 10A fuse would be right...
Click to expand...
Thanks that is helpful.
They just have had some other extras before as I don’t understand the need for a 35a fuse. Surely would have been a better precaution to have a lower one in case of shorts.

I have looked at some threads about conversions and it fills me with dread! I do however need to replace the bulkhead so that might be a good point to do it. I just don’t like electrics.
 
@new to all this , the other choice you have is to replace the aged glass type fuses with a modern blade fuse holder and correctly sized fuses. You'll find blade fuses are more robust than glass fuses. I and many others have done this, it's quite straight forward and enables you to clean & tidy up the fuse box wiring. My LR is also a 1987 Ninety, now fitted with one of these

https://www.carbuilder.com/uk/search?q=fuse+box
 
v8250 said:
@new to all this , the other choice you have is to replace the aged glass type fuses with a modern blade fuse holder and correctly sized fuses. You'll find blade fuses are more robust than glass fuses. I and many others have done this, it's quite straight forward and enables you to clean & tidy up the fuse box wiring. My LR is also a 1987 Ninety, now fitted with one of these
Click to expand...

Agreed. The glass fuses are a pain in the neck. Do it properly, once, and just fit a new blade fuse box, and get rid of the mess that was there before.
Just make sure you label every wire really well as they come off.
Also a good way to check that you have everything you should have, and don't have anything extra! You never know what someone has done before you...
 
v8250 said:
@new to all this , the other choice you have is to replace the aged glass type fuses with a modern blade fuse holder and correctly sized fuses. You'll find blade fuses are more robust than glass fuses. I and many others have done this, it's quite straight forward and enables you to clean & tidy up the fuse box wiring. My LR is also a 1987 Ninety, now fitted with one of these

https://www.carbuilder.com/uk/search?q=fuse+box
Click to expand...
That sounds interesting. I will need to make peace with my wiring at some stage and blade fuses do sound easier to get on with.
 
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