Clive Posted May 23, 2019 Report Share Posted May 23, 2019 This is a real tale of woe.. Last Wednesday I had popped a few essentials (hi-vis jackets, tools, spares etc etc) into my spitfire ready for Spa. Mid afternoon I took it for a quick spin to check everything was OK and fill with fuel. Only to have massive plumes of smoke emerge from under the bonnet and dash whilst making "good progress" along the local bypass. I switched ignition off, coated into a handy layby and very rapidly got the battery disconnected. A quick inspection showed all the brown, unfused wires had melted off their insulation (to put it mildly) I got recovered home, swapped stuff into my toledo, and took that although was an hour late picking up my passenger... So my task on the car is to get the spare loom I have installed. However, I would like to add an additional set of fuses to protect the supply to the car. That means I need to know some current requirements for the "bigger" electrical items. The headlamps are already on relays, as is the electric fan. Supplied by a small extra fusebox. Which is handy... but I may integrate these into the new fusebox. So can anybody suggest what current or power the heater motor, wiper motor and pair of horns require? I don't think there is anything else "significant" as the ECU, stereo, and other lights all add up to very little.... or have I missed something? (I should mention that the loom incident happened 2 days after I got recovered from from Scotland with a failed prop UJ. The prop was fitted with heavy duty ujs, and was just 2 years, 10K old. Ouch) Link to comment Share on other sites More sharing options...
Pete Lewis Posted May 23, 2019 Report Share Posted May 23, 2019 Clive thats bad luck any clues where it shorted out ? Fan not a lot wipers on load around 5amp horns probably good bit more maybe 10amps My lucas manual does not list/ give current useage Just a bit of a guess Pete Link to comment Share on other sites More sharing options...
dave.vitesse Posted May 23, 2019 Report Share Posted May 23, 2019 I agree with Pete on the values given. The problem with the starter motor in the Triumph WM is only an offload figure is given. I guess the load is inverse to the amount of rain. More rain less load! Dave Link to comment Share on other sites More sharing options...
Clive Posted May 23, 2019 Author Report Share Posted May 23, 2019 No idea yet. Car was shoved in the garage and abandoned in disgust. Not had a chance to take a proper look since I got back, though my memory came up trumps with the location of the spare loom. Saturday may reveal the issue, but my glance over the car while waiting for recovery (only 45 mins then 10 mins home) had the alternator main wire, plus ALL the brown wires on the solenoid plus under the dash are toast. I intend adding a maxi blade fuse to the alternator (probably a 60A fuse) The lighting feed can get a 10A fuse as headlights are relays/seperate fuse. The ignition switch can get a 30A, that should be plenty. And it seems the "purple" wiring is already fused. As indeed is the "green" wiring, which feeds the wiper motor, but the heater motor is totally unfused (I think from the diagrams) I guess I could reduce the fuse for the ignition switch, then add fused relays to the circuits fed from the ignition switch. That may be overkill? Link to comment Share on other sites More sharing options...
dave.vitesse Posted May 23, 2019 Report Share Posted May 23, 2019 Not good, still no fire that is good. If I remember Lucas used blow on 35 amps for heavy wiring/current and blow on 25 amps on the lighter wring/current. Radio of the time were blow on 5 amp. This was on the three fuse set-up. Doug did a lot of detailed work on his GT6 re fuses and may be able to give some more relevant input. And I thought he was only into software. Dave 1 Link to comment Share on other sites More sharing options...
NonMember Posted May 23, 2019 Report Share Posted May 23, 2019 The important thing is where the fuses are placed. If you've had a dead short of the brown wiring, somewhere, it's likely to have been chafed insulation. This can happen at any point (my old Dolomite 1850 had a 1500 loom with the main power distribution in a plastic housing which fell off the wing and landed on the exhaust manifold...) The fuse is only any good if it's between the battery and the fault. So most modern cars now have a big (100A+) fuse immediately on the battery terminal. It would be worth a last resort heavy fuse between the solenoid terminal and the cluster of brown wires. You probably aren't going to put a fuse in line with the starter motor so you just need to be careful to look after the battery cable. Link to comment Share on other sites More sharing options...
JohnD Posted May 23, 2019 Report Share Posted May 23, 2019 Clive, I added an eight-fuse box to SofS, allowing me to fuse many more systems than Triumph ever bothered with. To choose a suitable fuse value, I started with a very low one, and increased the rating until I found one that didn't blow. Then fitted one double that value, or about. Blade fuses are cheap and avaiable in many values. John 1 Link to comment Share on other sites More sharing options...
Clive Posted May 23, 2019 Author Report Share Posted May 23, 2019 9 minutes ago, NonMember said: The important thing is where the fuses are placed. If you've had a dead short of the brown wiring, somewhere, it's likely to have been chafed insulation. This can happen at any point (my old Dolomite 1850 had a 1500 loom with the main power distribution in a plastic housing which fell off the wing and landed on the exhaust manifold...) The fuse is only any good if it's between the battery and the fault. So most modern cars now have a big (100A+) fuse immediately on the battery terminal. It would be worth a last resort heavy fuse between the solenoid terminal and the cluster of brown wires. You probably aren't going to put a fuse in line with the starter motor so you just need to be careful to look after the battery cable. Yes, I am going to take a wire (or more likely 3 or 4) from the n=battery positive to the std fusebox position, then use appropriate sized fuses. A little headscratching as the existing loom has previously been modified. Add to that my ECU installation, it may get complex (though the ECU is only one wire to the original loom). But I will "tidy" the spare loom removing the unused bits. Once I have taken off all the pre-existing "improvements". I feel the dining room table will be in use for a day or 2.... John, I already have an extra 4 fuses for headlight relays, an ecu supply via the ignition switch, fuel pump, and something else which escapes me at the moment. But making sure the loom is fused "at source" should provide basic protection... Link to comment Share on other sites More sharing options...
dave.vitesse Posted May 23, 2019 Report Share Posted May 23, 2019 A point to be aware of is the original Lucas fuses are rated at their blow current. i.e. 25 amps blow 12 amps continues, 35 amps blow 17 amps continues. The fuses used in electrical, electronics and radios are usually marked as the continues rating. The blow rating will of course be higher, usefully the glass type are slightly longer than the Lucas type, so keep an original fuse as reference. I must measure both at some time. Dave Link to comment Share on other sites More sharing options...
rlubikey Posted May 23, 2019 Report Share Posted May 23, 2019 For ultimate cable protection, I have a CF8 fuse on a special battery terminal - you can't get much closer to the battery than that! You can even get a double post terminal - one for the starter and one for the rest of the car. Cheers, Richard 1 Link to comment Share on other sites More sharing options...
Anglefire Posted May 23, 2019 Report Share Posted May 23, 2019 Clive. Essentially don’t worry too much about what stuff pulls. Fuse to below the maximum capacity of the wiring. If you use 1mm2 cable then it will pull about 10a. So fuse at either 10 or less. (Less ideally!) This is us but will give a clue as it shows both awg and sq mm https://www.engineeringtoolbox.com/wire-gauges-d_419.html 1 Link to comment Share on other sites More sharing options...
Clive Posted May 23, 2019 Author Report Share Posted May 23, 2019 I have just ordered one of these (inspired by Richards idea) https://images.app.goo.gl/fM8QvqD1nsCNV9A16 Hopefully that will enable me to connect to alternator/extra fusebox plus the existing connections, giving strong basic protection. At least that is the plan... Mark, fair point, but I want to make sure the wire is big enough to cope with the demands on it. I suppose I can measure the actual wires already there, and work from that. Anyway, plans are evolving, in a good way. So thanks all. it really helps to bounce ideas about Link to comment Share on other sites More sharing options...
Blitz Posted May 23, 2019 Report Share Posted May 23, 2019 (edited) 6 hours ago, rlubikey said: For ultimate cable protection, I have a CF8 fuse on a special battery terminal - you can't get much closer to the battery than that! You can even get a double post terminal - one for the starter and one for the rest of the car. Cheers, Richard As an electrical noob has you give some more details please. Ie product links and what amp fuse to use? Edit top pic of fuse didn’t load up but can see it now. Thanks Edited May 23, 2019 by Blitz Link to comment Share on other sites More sharing options...
Anglefire Posted May 23, 2019 Report Share Posted May 23, 2019 37 minutes ago, clive said: I want to make sure the wire is big enough to cope with the demands on it. I suppose I can measure the actual wires already there, and work from that. I was only using 1mm as an example. And if you use tri-rated on any new circuit, it is both more flexible and smaller for a given current carrying capacity. Measuring the existing wire is not that simple - you need the copper x-section not overall. But yes I was forgetting you aren’t using new wire but a replacement loom containing new Lucas smoke. 😂 Link to comment Share on other sites More sharing options...
dougbgt6 Posted May 23, 2019 Report Share Posted May 23, 2019 Clive, I put in a 10 way blade fuse box in my GT6, there are a number of threads on here detailing the same journey. I used this diagram and split the existing fuses as red group (3), purple group (3) and green group (4). This is the box, the LED comes on when the fuse is blown. Neat! This is how I wired the box. (Laminated copy inside the box!) Currently (Ha!) Gauge lights are all LED so 5, pea bulbs might need more. Originally horn was 10 but blew and I upgraded to15. Separate in line main/dipped beam 10, but flasher blew at 10 and 15 so upgraded to 25, might be too much. Along the way I found these estimates of assorted current requirements. Doug 1 1 Link to comment Share on other sites More sharing options...
Clive Posted May 23, 2019 Author Report Share Posted May 23, 2019 That is very helpful, thanks Doug. Link to comment Share on other sites More sharing options...
rlubikey Posted May 24, 2019 Report Share Posted May 24, 2019 Blitz, the 50A fuse was just the first good image I found - there's no significance to that current (though I think that's the minimum available). The purpose of fuses is to protect the wiring. So as Angelfire says, you size to a bit below the cable capacity, although if you know the maximum current of the ancillary(s), you size a little above that. I used 200A for the starter and I think 75A for the rest, but that includes power steering (50A). Downstream of these I have a proper fusebox with modern blade fuses for each circuit. CF8 fuses are made by Litelfuse, Pudenz and Wickmann, though I think there's been some buying of companies since then. I got mine through either RS, Farnell or CPC, but I'm sure you would find them on Fleabay & elsewhere. Cheers, Richard Link to comment Share on other sites More sharing options...
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