Fusible links

[1972nail]

Has anyone swapped the 2 fusible links on a later twin headlight car for something more modern - circuit breakers or blade type fuses?

[dann01]

Haven't done it, but see no reason why it can't be? Probably better to put the lights on a relay though.

In fact I wonder why they them in the first place, since there is already a thermal cut out on the lighting circuit.

Dan

[1972nail]

Yeah Dan, I'm going to fit relays to dip and main beam as well. Other relays I'm considering are the fan blower, HRW and an electric rad fan, so that the load going through the ignition switch can be reduced.

I'm also bypassing the resistance wire in the loom so that I can run a 12V coil and electronic ignition safely. I had one loom burn out because of it in the past so I think it is a very worthwhile safety upgrade.

However, I'm having difficulty finding the rating of the fusible links so that I can select suitable alternatives, anybody know what they are rated at?

[dann01]

Already had the resistance wire problem... Reared it's ugly head during the Lejog drive we did a couple of years back, of all times... If you are gonna strip out altogether, expect to have to take the loom out entirely, cos, seriously, it weaves all over the show in there.

Dan

[1972nail]

Already had the resistance wire problem... Reared it's ugly head during the Lejog drive we did a couple of years back, of all times... If you are gonna strip out altogether, expect to have to take the loom out entirely, cos, seriously, it weaves all over the show in there.

Dan

The loom is sitting on the garage floor so easily accessible! You're right it travels about a bit, anyone with a fried loom can tell you all about it's route!

Looking at the wiring diagram and testing with the multimeter it is just a simple job of swapping the wire on pin D4 to pin D5 on the engine loom connector in the fuse box. Pin D5 is already connected to the same feed from the ignition switch as the resistance wire and is just sitting there free to be used!

That means that the resistance wire is just left unconnected in the loom and therefore harmless. I hope I'm right!

[1972nail]

The Americans seem to be very into wire type fusible links, just like those fitted to the Viva range! So a bit of research found out that they are generally sized 4 AWG lower than the wire they are there to protect, that works out about half the cross sectional area.

So looking at the Magnum 7 Dial wiring diagram the wires which the 2 links protect are 44/0.30 and 35/0.30 which are 13.2 and 10.5 mm2. These are rated at 37A and 30A.

The links in the Magnum 7 dial wiring loom are 14/0.30 - 4.2mm2 which is rated at only 12A. This seem seriously low until you realise there are 2 of them and that the links don't 'blow' immediately, like a fuse, but will take quite high voltage spikes for a few seconds without harm. Whereas a standard fuse will blow almost immediately. The links are in essence 'slow blow' fuses.

So where does that leave me with the choice and rating of fuse or other safety device to replace the links with? It's got to be more than 12A but how much more?

Just to point out that the wiring of single headlamp and early 7 dial cars only seem to have one fusible link of 35/0.12 - 4.2mm2 rated at 12A.

[droopsnoot]

That means that the resistance wire is just left unconnected in the loom and therefore harmless. I hope I'm right!

I believe you are. Or I hope you are, that's what I did with mine. I didn't like the dash loom getting warm and I couldn't get a 100% definitive answer on whether it should, so I dropped the resistance wire and stuck a ballast resistor on the side of the coil. Doesn't matter if that gets a bit warm, being bolted to the engine. Resistance wire is still in place, but unused. My dash loom had been fried, but by a previous owner connecting something big to the dash lighting wire.