Scotland Director Posted July 7, 2020 Report Share Posted July 7, 2020 Just wondering, has anyone upgraded their old style fuse box for something different that has blade fuses and a place for holding some extra relays. That part of my engine bay is a bit messy, assuming I can of course actually open the bonnet, but that’s a whole story in itself. Don’t go there ! Appreciate some advice and maybe some pictures. Thanks. Quote Link to post Share on other sites
Richard Green 54 Posted July 7, 2020 Report Share Posted July 7, 2020 Having had smoke coming out of the heater vents when driving back from collecting my car in January I decided to replace the fuse box. I fitted a 6 blade unit purchased from eBay and separated out some of the circuits. In the process I also downsized some of the fuses to protect the wiring. None of the new fuses have blown yet. I also added a couple of additional in-line fuses to protect specific wiring runs. In total the car now has around 10 fuses. Quote Link to post Share on other sites
ed_h Posted July 7, 2020 Report Share Posted July 7, 2020 Its more of a departure from stock, but I moved all of the fuses and relays, and added quite a few new ones to a box. This is a LHD car, though. Ed Quote Link to post Share on other sites
foster461 Posted July 7, 2020 Report Share Posted July 7, 2020 I left the factory wiring mostly alone but added an auxilliary fuse and relay panel in the passenger footwell (we are both short..). The new panel has relays and fuses for the fog and spot lamps, relay for the fan and a relay for a second fuse panel that powers a bunch of stuff like power outlets, audio system etc when the ignition is on. Stan Quote Link to post Share on other sites
Richard Green 54 Posted July 7, 2020 Report Share Posted July 7, 2020 So that's three completely different solutions then What they do have in common is that each is an improvement on the original and likely to be less smoke generating. Quote Link to post Share on other sites
stuart Posted July 7, 2020 Report Share Posted July 7, 2020 1 hour ago, ed_h said: Its more of a departure from stock, but I moved all of the fuses and relays, and added quite a few new ones to a box. This is a LHD car, though. Ed Hope thats water tight as Ive had trouble with a certain companies auxiliary fuse board that they like to fit in that location filling up with water when used in heavy rain. Stuart. Quote Link to post Share on other sites
ed_h Posted July 7, 2020 Report Share Posted July 7, 2020 I guess time will tell. Its got a closed cell foam seal around the perimeter, and the cable entrance has a formed resilient seal, not shown in the pics. I do avold driving it in heavy rain, but you never kmow. Ed Quote Link to post Share on other sites
Paul Hill Posted July 7, 2020 Report Share Posted July 7, 2020 (edited) Here’s mine Edited July 7, 2020 by Paul Hill Quote Link to post Share on other sites
foster461 Posted July 7, 2020 Report Share Posted July 7, 2020 My aux panel in the footwell. It gets power via a big ass cable that comes off the multi-way connector integrated into the battery cable. I did this so long ago I had forgotten that the fan relay is in the engine bay close to the fuse box. I did that before I installed the aux panel. The fan power does come from a fuse on the panel however. The enclosure is just deep enough to accommodate the relays and gets covered by the carpet. The fuse panels and the relays etc are mounted on a piece of Compaq server blanking plate, about 1/8 inch thick aluminum. I removed the cover so I could take the picture. Quote Link to post Share on other sites
Prefect Posted July 8, 2020 Report Share Posted July 8, 2020 The above solutions are very smart but in my opinion there is a more serious TR6 Loom error to address: The Brown Wire is a 12V UNFUSED +ve from a connector near the Battery post, it supplies: - · The purple wire 40A fuse whose circuit includes the Horn, Interior Light, boot light, headlight flasher. · The red wire 40A fuse (via the headlight switch) this circuit includes Front Sidelights, instrument lights · The Brown wire feeds the ignition switch (unfused) which in turn connects it to the white wire, whose circuit includes the fuel pump, coil, distributer, headlight switch and connects to the Alternator warning lamp and the auxiliary (radio) circuit. · The white wire also goes on to supply: - The green wire 40A fuse whose circuit includes The Overdrive, Wipers, Heater motor, Indicators, temperature and fuel gauge. The Brown and White wires are unfused! They run in the loom under the dashboard . If shorted to earth due whatever reason (connector being pushed off or wire trapped or screwed into !!) the circuit in the loom back to the battery would firstly smoke then catch fire. There is nothing to prevent this. This would never be allowed in a modern car. I show a photo a friends car which had a Brown wire short near the radio he could have lost the car to fire... I also show a fusing arrangement for Brown wire circuits which would clear this type of fault. Quote Link to post Share on other sites
barkerwilliams Posted July 8, 2020 Report Share Posted July 8, 2020 (edited) I am given to understand that the unfused brown is not an error but by design. It is unfused to prevent a fuse blowing and taking out the headlights which is quite serious at speed. I presume the rationale was that a loom fire is better than driving blind, a loom design practice that was common at the time. I believe that modern cars address the same issue by having multiple individually fused circuits, main, dip, left headlight, right headlight to have some electrical redundancy in the case of electric failure. Whatever the reasoning it would not be good practice to feed the headlight via a single fuse. Alan Edited July 8, 2020 by barkerwilliams Quote Link to post Share on other sites
Prefect Posted July 8, 2020 Report Share Posted July 8, 2020 Dear Alan I Understand that the Lucas wiring loom has its roots in Tank wiring where there were no fuses to my knowlege. Thereafter the lack of confidence in fuse holders pushed the designers down the route you descibe. Now, we as current temporary owners of out TRs, dont have to accept their pre war concepts and risk fire. Fuse the +ve supplies with reliable 40A fuses and holders and whatever else you fancy we will all be safer. Quote Link to post Share on other sites
RobH Posted July 8, 2020 Report Share Posted July 8, 2020 Alan is quite right that if possible the circuits should be fused individually and not with a single fuse feeding everything. That may be difficult to achieve with a standard TR wiring loom though. Trying to protect a number of lower-current circuits with a single high value fuse is not a good way of doing things. You should be aware that blade fuses do not blow at the current printed on them - that is the current they will carry more or less continuously without blowing. A 40A blade fuse may happily pass 60A for some minutes or 80A for five seconds before it blows - enough time for damage to occur to wire insulation on thinner circuits downstream where the fault may be. The original glass automotive fuses fitted to TRs actually blow at the stated current so need to be of a higher current rating to give the same service. Quote Link to post Share on other sites
ed_h Posted July 8, 2020 Report Share Posted July 8, 2020 (edited) It is true that there are two schools of thought on fusing headlights. You can find examples of each in cars of the era, and in aftermarket products designed for them. The route I chose was to provide separate relayed and fused circuits for the low and high beams. The "flash to pass" is yet a third circuit. This of course assumes i would have the presence of mind in a sudden blackout situation to hit the high beams or pull the flash lever. One other downside of the three-fuse system is the situation alluded to above where a partial short or other malfunction in a branch circuit could pull a current high enough to melt the insulation on the small branch circuit wiring, but not enough to blow the largish fuse. The only practical solution to this is more fuses for individual circuits. Ed Edited July 9, 2020 by ed_h Quote Link to post Share on other sites
Richard Green 54 Posted July 9, 2020 Report Share Posted July 9, 2020 The logical and modern solution is to have a system of cascading fuses where each fuse is rated for the specific demand. The biggest fuses at the battery end and reducing to protect circuits with lesser demand. The fuses need to have the correct rating to protect the decreasing wire sizes. Otherwise you get a fire. I personally think that the brown wires to the ignition and light switches should be protected to stop the relatively long wire runs shorting out and causing a fire. The idea that the headlights would continue to work if that part of the circuitry was on fire seems somewhat flawed to me. At a pure risk assessment level you also have to consider what proportion of the time you drive your TR in pitch black darkness. This should then be compared to the risk of a harness fire in a 45+ year old car. I had a problem many decades ago with a Triumph Herald. The lighting circuit wiring had shorted out at the front of the car due to chafing caused by the front hinged bonnet. I got in the car at work one evening and turned on the lights. At that point it was game over. Nothing you could do apart from get out of the car and wait for the wiring harness to burn through. I was very lucky that the car did not burn to the ground. But the extent of the wiring damage was significant and ran all the way from the front of the bonnet to the light switch on the dashboard. Quote Link to post Share on other sites
stuart Posted July 9, 2020 Report Share Posted July 9, 2020 If you buy a new loom most of the loom manufacturers will supply them with the circuits split down and relayed and fused however you want. But you do have to fit the loom properly so that the risk of chafing etc leading to a short is negated. Going to LEDs all round also lessens the draw through the loom as well. Stuart. Quote Link to post Share on other sites
Prefect Posted July 9, 2020 Report Share Posted July 9, 2020 (edited) Dear All I believe there are two issues here Manage the unfused wires in the loom to avoid fire risk. Fuse seperate components as required. My view is that 1 is essencial and 2 optional. The Operating time of modern Auto Blade fuses is shown on the table attached they are very precise even in high temp engine bays. The old 1 1/4 Glass fuses fitted to our cars have characteristics as shown below . They are not so good at high temperature engine bays. My goal was to prevent fire so therefore I fitted 40A. They will blow in less than a second for a short circuit in the brown or white wires. Edited July 9, 2020 by Prefect To add Glass fuse characteristics Quote Link to post Share on other sites
jerrytr5 Posted July 9, 2020 Report Share Posted July 9, 2020 Drop down panel in passenger footwell for me. Jerry Quote Link to post Share on other sites
Richard Green 54 Posted July 9, 2020 Report Share Posted July 9, 2020 Blimey Jerry, there are more wires in that than in your XKR Quote Link to post Share on other sites
RobH Posted July 9, 2020 Report Share Posted July 9, 2020 That table for glass fuses is the wrong one 'Prefect'. The glass fuses we should be using in TRs are the Lucas Automotive type . They are marked with the continuous current at which they will blow. A Lucas fuse marked 10A is intended to carry 5A and will blow at 10A . Unfortunately these fuses look exactly the same as the ones your table refers to. It is likely that over the years many TRs have been fitted with new fuses which actually have twice the current capacity than was intended by the designers of the wiring: Quote Link to post Share on other sites
PodOne Posted July 9, 2020 Report Share Posted July 9, 2020 Hi Jerry That's a nice neat set up you have there. Have you modified the "old" loom or had a loom made to allow everything to be fused separately? Andy Quote Link to post Share on other sites
Prefect Posted July 9, 2020 Report Share Posted July 9, 2020 Hi RobH Thank you for pointing out my error. I am trying to spark a conversation about fusing the Brown Wires, and failing. Guys seem obsessed with very smart fuse boards but leave yards of un-fused cables in the loom. Doh! Quote Link to post Share on other sites
foster461 Posted July 9, 2020 Report Share Posted July 9, 2020 44 minutes ago, Prefect said: Hi RobH Thank you for pointing out my error. I am trying to spark a conversation about fusing the Brown Wires, and failing. Guys seem obsessed with very smart fuse boards but leave yards of un-fused cables in the loom. Doh! You have raised a good point and I appreciate the discussion. My truck has over 100 fuses in two large fuse boxes and even the individual features of the seats have their own fuses. Stan Quote Link to post Share on other sites
jerrytr5 Posted July 9, 2020 Report Share Posted July 9, 2020 2 hours ago, PodOne said: Hi Jerry That's a nice neat set up you have there. Have you modified the "old" loom or had a loom made to allow everything to be fused separately? Andy Thanks. I spent some time drawing a wiring diagram so that almost everything was individualy fused and/or relayed, then I bought a load of different cable colours and connectors and started cutting and soldering. Not practical or desirable to modify the old loom. If only I was able to get hold of the thinwall cable at the time it would have made the 'packaging' easier. Also swapped the ammeter for a voltmeter as that big fat cable snaking behind the dash always seems a liability. Of course having finished it with every conceivable electrical accesory, I then added heated seats for which I'd run out of fuseways. 1 hour ago, Prefect said: Hi RobH Thank you for pointing out my error. I am trying to spark a conversation about fusing the Brown Wires, and failing. Guys seem obsessed with very smart fuse boards but leave yards of un-fused cables in the loom. Doh! If you look at the front of the panel there is a large brown wire going through a mini circuit breaker before powering up the main busbar. nah, nah nenah nah. 5 hours ago, Richard Green 54 said: Blimey Jerry, there are more wires in that than in your XKR Not quite, now that is a different kettle of fish & I'm not touching it unless I have to. Jerry Quote Link to post Share on other sites
Prefect Posted July 9, 2020 Report Share Posted July 9, 2020 Hi Jerry Not a dig at you, a general obsevation, but your CB would best placed nearer the battery. If the car was in an accident. What rating is it? Quote Link to post Share on other sites
Recommended Posts