Fuses

[David Moult]

Like everyone else I have had problems with the series 2 fuse box. Melting, intermittent etc.
I have found that modern Chinese glass fuses are a smaller diameter than the old Lucas ones.
I have replaced them all with Flexi Fuse replacements from the US. They convert glass fuse to blade fuse.
A much tighter fit. You can't have the lid on the box though.
After the fuse box melted at the headlight connections I cut away the melted bits and padded out between with dense neoprene sponge.
I also replaced the halogen units with LED's which have a drastically lower wattage and remove the need for relays and extra wiring.

 

[jp928]

I did try those flex fuses a few years ago - when I had slid the ends out to suit our sockets I felt the engagement of the actual blade fuse legs was inadequate, so I sent them back, and made my own version. Hope you have better luck - maybe they are better now?

 

[DaveRover3500s]

I do think that with the series 2 fuse box you’re better off taking as much of the loads away from it! Especially main beam inners (LED as has been said can tick that box and bring load down by 50%) but I would also look at HRW and heater fan blower motor and possibly wipers. 3 of highest current circuits that all feed from ignition contact No.5 and split at the rear of fuse box to the 3 fuses. Seen couple fuse box melt here. Fitting a 6 way fuse box near original fed via either the shunt behind dash or direct battery feed and 30 amp fuse allows, via use of relays, all high current circuits to be removed from the original fuse box, while keeping it in use to provide fuse protection to the tiny relay trigger feeds for each relayed circuit.
My top 6 would be: Dip and Main beams, HRW, Heater Blower, Wipers. Fit and forget!

Dave

 

[jp928]

As well as relays on main, dip and horns, I have also converted the lights to LED all around. I tapped the relay supply off the big wire to the light switch and have a 40A resettable breaker in the lead to the relays.

 

[DaveRover3500s]

That’s very wise - 40a breaker on the relay feed. Yes the lighting wire direct from the shunt behind the clocks/dash is decent gauge.
I think you also said you fused the hazard warning feed? What a great idea it made me think and look again at this on wiring diagram ( 1975 series 2 3500S) and yet another unfused circuit! Brown unfused feed direct from shunt to back of fuse box to feed the Battery Control fuse - but tap off this feed to hazard warning flasher unit is not via the fuse. So I will be doing same and fusing this circuit thanks for heads up.
A really lovely 1974 3500S with 37000 miles and really stunning example recently was sadly lost to a catastrophic electrical fire in the cabin which took hold in seconds. I have seen video and pics it’s unreal how fast it was lost. It’s not fully clear what occurred but we do know the drivers knee box was opened to retrieve an item and something was hanging down unsecured - could been flasher unit for hazards- next thing it came into contact with the body and arching started to occur with smoke and fire. This quickly transferred to the fuse box and this caught fire fed by local combustible material. Fire was uncontrollable within 1 min and after 5 mins complete interior was ablaze. Fire brigade put out before tank exploded but of course complete write off. Horrific. A fused circuit could saved this.
It’s hard to understand thinking now as to why hazards were not included in battery control fused circuits but must been some logic to it.

Thanks for bringing it into focus John.

Dave

 

[jp928]

I dont recall saying (or doing) that I fused the hazard thing, but I will look into it asap, thanks. Pretty sure mine is properly secured. Unfused stuff sounds like afterthoughts, or even worse, nothoughts. I have seen an alarm circuit protected by a 1A fuse.....?
This is what happens when an alloy engined car suffers a real conflagration - 928 in a fire in US a few years ago.

Checking the wiring diagram I have the indicators/hazard seem to come off fuse 20 (fused side), where ignition, tacho, brake warning light etc come off the unfused 19 end..?

 

[DaveRover3500s]

I dont recall saying (or doing) that I fused the hazard thing, but I will look into it asap, thanks. Pretty sure mine is properly secured. Unfused stuff sounds like afterthoughts, or even worse, nothoughts. I have seen an alarm circuit protected by a 1A fuse.....?
This is what happens when an alloy engined car suffers a real conflagration - 928 in a fire in US a few years ago.

Checking the wiring diagram I have the indicators/hazard seem to come off fuse 20 (fused side), where ignition, tacho, brake warning light etc come off the unfused 19 end..?

lol sorry John! Your right of course I just had a think - I got it (the hazard warning non fused feed) from a local chap who has done many P6 rewire mostly due to fuse box melt downs or poor mods leading to damage. Apologies!
The 928 fire - ouch ain’t much left there!

 

[DaveRover3500s]

I dont recall saying (or doing) that I fused the hazard thing, but I will look into it asap, thanks. Pretty sure mine is properly secured. Unfused stuff sounds like afterthoughts, or even worse, nothoughts. I have seen an alarm circuit protected by a 1A fuse.....?
This is what happens when an alloy engined car suffers a real conflagration - 928 in a fire in US a few years ago.

Checking the wiring diagram I have the indicators/hazard seem to come off fuse 20 (fused side), where ignition, tacho, brake warning light etc come off the unfused 19 end..?

Sorry John I never replied to your wiring diagram question. I attach screenshot of relevant part of wiring diagram for a Series 2 late V8 3500 and 3500S RHD. Mine is 1975.

The brown wire from shunt feeds top fuse 47 (fuse 1-2 battery control) you can then see a tap off this that is also brown that feeds to Hazard flasher relay - 58. This I have checked on my car and on one I was working on last 2 days also N reg and can confirm diagram is correct. Not helpful that both are brown and look to be same gauge as identifying which one is feed from shunt coming into fuse box and which one heads off to the hazard relay is more difficult! I have decided to fit an in line 10 amp fuse just where hazard relay feed wire leaves fuse box connection - and ensure fuse is where I can get to it without having to move or undo things!

I prefer wat your car has been wired - better protected! Must be different wiring diagram for your year and export model.

Cannot understand why the hazard circuit was not taken from bottom of battery fuse or provided with its own fuse. I would urge anyone with same year wiring (re late series 2 think mine is suffix E on) to consider fitting simple in line fuse to the hazard feed. Even if in line fuse fitted over at drivers side where brown wire leaves loom and before it connects to hazard relay - this would protect 95% of the circuit.

Dave