The 'E' Type Forum

Having replaced the engine looms as part of my winter refurb I am keen to add a fuse at the battery for some extra security for the first switch-on.

What amp rating should I use in this fuse please?

thanks
Ash

Hi Ash,

When I did mine with a new Autosparks loom, I used a modern 100amp fuse for the starter motor feed and believe it or not a modern 15amp blade fuse was adequate for the rest of the loom even when the fan kicked in. That way every part of the loom(s) was protected for initial testing. I just made up two jump leads with fuse holders.
It’s quite frightening how much of the wiring is NOT fused especially behind the dash.

Hopefully that makes sense.

Simon

Thanks Simon.

I have found these neat fuse holders that are attached to the positive terminal of the battery. I don’t want to turn the car over (the engine builder won’t let me ) just try all of the circuits with ignition on.

So 15amp would do then?

Cheers
Ash

15 Amp would do but rather than using a fuse I'd suggest using a headlamp bulb instead. It's brightness (or not) gives a more immediate indication of any problem and if you do have a problem offers an easier way forward as you try to eliminate it without replacing endless fuses.

Another option if you use a blade type fuse holder would be to use a resettable fuse or a thermal fuse for your initial checks.

Hi Ash,

For initial testing of each individual circuit I used a multi meter to check for any dead shorts. Once all that checked out, I used the 15 amp blade fuse and tested each circuit function individually. My only non standard items drawing current are twin high flow fans and electronic SU fuel pump. I also have a modern alternator and high torque starter motor. The 15 amp fuse aleven withstood a few blasts on the horn to check it.
I did manage to blow an 80 amp fuse for the starter once with prolonged cranking to check for oil pressure before actually firing the engine up but the 100 amp one seems fine.

This is what worked for me after a bit of basic maths but I’m sure others like Marek will be able to give you more specific fuse ratings if needed.

Just seen John’s reply, that’s another option.

Simon

Thanks for the feedback; all very helpful.

Much appreciated as always.

cheers
Ash