Alpha206 Posted February 13, 2011 Report Share Posted February 13, 2011 Hi all, Fired up the Six again after a couple of months of inactivity, then noticed the fuel gauge, indicators and subsequently the temperature gauge weren't working, which I rapidly narrowed down to a blown 35A fuse. (Have to say, I was quite chuffed at my diagnostic skills for once! ) Naturally I didn't have a spare so checked the Brown Bible for the correct rating which states 35A for all 3 - although the other 2 in the car are rated at a lower amperage. Question is, which is correct? The lower-rated fuses have been doing the job OK and I'm happy to leave them as they are potentially safer. Quote Link to post Share on other sites
ianhoward Posted February 14, 2011 Report Share Posted February 14, 2011 (edited) Hi I believe all TRs have 35A fuses in all circuits... makes it easy! Not at home to check the bibles etc. though! Brgds Edited February 14, 2011 by ianhoward Quote Link to post Share on other sites
AndrewP Posted February 14, 2011 Report Share Posted February 14, 2011 (edited) From what I remember, you shouldnt use a modern rated 35A fuse. The modern equivalent rating to a Lucas 35A fuse is ~17.5A (or 20A)..this rating being the continuous current rating for the fuse. Both still blow @ 35A. If you buy a modern 35A rated fuse however, it will blow @ >60A. This can result in looms melting etc etc. More info here:- Wikipedia Auto Fuses ~ Lucas Type and http://www.triumphspitfire.com/Fuses.html I have all 20A glass fuses and all runs fine, but you make your own decision. Personally Id rather err on the side of caution and fit a lower rated fuse and make decisions from there. Cheers Edited February 14, 2011 by AndrewP Quote Link to post Share on other sites
ianhoward Posted February 14, 2011 Report Share Posted February 14, 2011 Oh Bug*er!!! And I though it was straight forward 35A/17A continuous... Quote Link to post Share on other sites
RogerH Posted February 14, 2011 Report Share Posted February 14, 2011 The Wiki list is interesting. It looks like Lucas have TRiumphed again in giving all the states of the fuse. In comparison the modern blade only gives one value - is this equivalent to the Lucas 'continuous fusing' current (what it says on the tin). As long as the loom is equal to the 'continuous fusing' current then all should be well. Alph - what caused you 35A fuse to pop. The gauges not working are the result not the cause. Roger Quote Link to post Share on other sites
Alpha206 Posted February 14, 2011 Author Report Share Posted February 14, 2011 The fuses are all the glass wire-type rather than the modern blade-type - I intend to replace with the same - any thoughts there? Don't know what caused it to blow as yet - when I took the fuse out one of the ends came away in my hand, so it could be the age of the fuse (my early suspicions are that it's an original fuse judging by the grime on it!) - but it is a TR6 after all! Quote Link to post Share on other sites
88V8 Posted February 14, 2011 Report Share Posted February 14, 2011 Replace like with like, glass with glass. It's been OK for 30+ years.... Ivor Quote Link to post Share on other sites
AndrewP Posted February 14, 2011 Report Share Posted February 14, 2011 (edited) I think thats the problem tho Ivor..Like isnt the same anymore. Lucas seemed to use their own standard that no-one else followed, so as to confuse the hell out of everyone else no doubt! As an example, Ive just checked a roll of 1.85mm2 (4mm) PVC auto cable I have, and the SAFE current is alleged to be 20A (continuous). Im pretty sure the TR loom isnt made up of 4mm cable, and given a short condition this will be the shortest path to earth/negative. This therefore needs to be able to carry 20A safely AND have the fuse blow to prevent any damage to wiring and/or equipment. Edited February 14, 2011 by AndrewP Quote Link to post Share on other sites
Yorkkie Posted February 14, 2011 Report Share Posted February 14, 2011 The issue is the so called "fusing factor"......... It appears that in 1970s manufacture the fuses showed the fusing current and the continuous operating current. Modern fuses show the maximum continuous current or Rated Current. More or at least as important than the current rating is the fuse characteristic this dictates the speed at which the fuse will blow (this is I*2t or square of the current x time). a high current over a short time will blow a fuse as will a lower current over a longer time. When old glass fuses blow you can look in side and see if the current was significantly over rating or marginal by the way in which the actual fuse strip has become open circuit. Replace like for like, smaller is better (but you may get nuissance blows). If you are not sure it is best to consult an electrical engineer. Regards Andy Quote Link to post Share on other sites
AndrewP Posted February 14, 2011 Report Share Posted February 14, 2011 --->Electrical and Control systems Engineer here Basically any system should be de-rated. That is the fusing current is LESS than the rated current for the supply cable. If we design a system (say 32A) with cabling sufficient for effectively x2 the nominal fusing current, then this would generally be supplied with a 16A breaker prior to the end equipment to protect cabling, infrastructure as well as end equipment. This design changes dependant on various things (i.e if its motor supply etc, the system needs to be able to handle motor startup current or use VVVF/soft starts etc), but the basics are the same. Anyhew, you makes your own choice. IF you stick a 32A fuse in, then the cabling HAS to be able to SAFELY handle that fault current. If it cant, IT WILL generate heat, possibly melting the cable and starting a fire. Without knowing the specs and type of cable used in the TR, I cant say for sure that it can, but 1.5mm cable can 'generally' handle approx 15A continuous...and thats new cable. Your choice.. Quote Link to post Share on other sites
Alpha206 Posted February 14, 2011 Author Report Share Posted February 14, 2011 I think we're going off at a bit of a tangent from my original question. Notwithstanding the merits of using lower-rated fuses and the differences between blade, Lucas and other suppliers and what a circuit can or can't handle, my situation is as follows: 1. A 35A Lucas glass fuse blew (for whatever reason) 2. I want to replace it with a Lucas glass fuse of the same rating 3. The Brown Bible says all 3 fuses should be 35A rated 4. The other 2 fuses are also Lucas glass ones BUT at lower ratings to that stated in the BB. Any ideas as to why the fuses may have been replaced with the lower rating from what was specified in the BB? And should I continue in this vein if they're doing the job OK? (BTW my fuel pump is on its own fused circuit!) Ref the comment "any system should be de-rated" - surely that de-rating is already designed into the system? Answers on a postcard.... Quote Link to post Share on other sites
Steves_TR6 Posted February 14, 2011 Report Share Posted February 14, 2011 I think we're going off at a bit of a tangent from my original question. Notwithstanding the merits of using lower-rated fuses and the differences between blade, Lucas and other suppliers and what a circuit can or can't handle, my situation is as follows: 1. A 35A Lucas glass fuse blew (for whatever reason) 2. I want to replace it with a Lucas glass fuse of the same rating 3. The Brown Bible says all 3 fuses should be 35A rated 4. The other 2 fuses are also Lucas glass ones BUT at lower ratings to that stated in the BB. Any ideas as to why the fuses may have been replaced with the lower rating from what was specified in the BB? And should I continue in this vein if they're doing the job OK? (BTW my fuel pump is on its own fused circuit!) Ref the comment "any system should be de-rated" - surely that de-rating is already designed into the system? Answers on a postcard.... No postcard to hand.... Personally i'd tot up all the loads on each fuse, not hard on a tr6 !, and fuse accordingly. At this point i thought about posting a photo of my new fuse and relay box...... but i'd get flamed again for the connectors ! Steve Quote Link to post Share on other sites
RogerH Posted February 14, 2011 Report Share Posted February 14, 2011 Hi Alph, if they appear to be working OK leave alone. They may have been de-rated by hobsons choice - that's all there were in the spares bin by a PO. I see you are connected to TRident 1C ARPO (is there a large skin repair patch on the keel just aft of the NLG bay). I spent my apprentiship on Tridents in the 60's at BEA. I thought they were fabulous aircraft, especially to work on. When the wings started to fall off the Trident 2's the NDT department of BEA were on the ball immediately - we found the first crack and then kept them flying by a very vigours inspection regime. Roger Quote Link to post Share on other sites
Alpha206 Posted February 14, 2011 Author Report Share Posted February 14, 2011 Thanks for that...will get my order in tonight! Roger, will check with the guys on G-ARPO! Thinking about it, you & I may have worked together briefly when I was an undergrad at BA - I spent about a month in NDT. Quote Link to post Share on other sites
Alpha206 Posted February 17, 2011 Author Report Share Posted February 17, 2011 Ok, so I ordered 25A and 35A Lucas glass fuses from Rimmers (http://www.rimmerbros.co.uk/Item--i-GRID006903 Part nos GFS3025/GFS3035) and got them today...except it's not a wire inside the cartridge but a flat strip - thinking of what people have said earlier in the thread about blade fuses, are these OK? Rimmers are selling them as TR6 fuses but naturally I don't want roast loom for Sunday lunch... Sorry to be a pain... Quote Link to post Share on other sites
Mike Atwell Posted February 4, 2017 Report Share Posted February 4, 2017 Hi All, Anyone have a picture or wiring diagram with colours of wires for a UK TR6 CR 1974 model. I took off my wires to change the fuse box and I thought I had carefully transferred the wires to the new fuse box, but now the park lights remain on. Quote Link to post Share on other sites
RogerH Posted February 4, 2017 Report Share Posted February 4, 2017 Hi Mike have a look here http://www.advanceautowire.com/tr2506.pdf Roger Quote Link to post Share on other sites
Mike Atwell Posted February 4, 2017 Report Share Posted February 4, 2017 HELP please. Any suggestions as to why park lights and dashboard lights come on as soon as I put the green/red wire onto the fuse box? Quote Link to post Share on other sites
Mike Atwell Posted February 4, 2017 Report Share Posted February 4, 2017 Thanks Roger, Are these UK cars? Quote Link to post Share on other sites
Mike Atwell Posted February 4, 2017 Report Share Posted February 4, 2017 Hi RogerH, According to that diagram for 74 TR6, I have the fuse box wired correctly. I think this wiring diagram is for the USA carburetor cars, as I do not see the high pressure petrol pump. Quote Link to post Share on other sites
peejay4A Posted February 4, 2017 Report Share Posted February 4, 2017 I don't suppose you've nudged the lighting switch on? Quote Link to post Share on other sites
stuart Posted February 4, 2017 Report Share Posted February 4, 2017 Hi RogerH, According to that diagram for 74 TR6, I have the fuse box wired correctly. I think this wiring diagram is for the USA carburetor cars, as I do not see the high pressure petrol pump. All of the Advance auto diagrams are for US cars but its easier than trying to read the only UK ones available on line that tend to be poor quality images and spread across 2 pages for the key. Stuart. Quote Link to post Share on other sites
astontr6 Posted February 4, 2017 Report Share Posted February 4, 2017 Hi Alpha206, First of all I am not certain if you are in the UK or North America by looking at that Police Van parked behind your red TR6?? But if you are in the UK, a company called Vehicle Wiring Products on page 43 of their cat. shows the 30mm (1.3/16") Glass Cartridge Wire Fuse rated at the same spec. as the old British Automotive Spec. i.e. a 17.5 continuous, fuse blows at 35 amp. Bruce. Quote Link to post Share on other sites
john.r.davies Posted February 4, 2017 Report Share Posted February 4, 2017 An interesting thread, to one who still thinks that it was Lucas who put the smoke in the wires. And here's another reason to go to the Vehicle Wiring Products site, as for each wire or cable they include the cross sectional area (mm^2), and the continuous current carrying capacity (Amps) The area is of course of the conductor, so not immediately obvious from the insulated wire, but anyway. If you can measure the conductor, then Area=Pi x (half the diameter)^2 So you can get a good estimate of the potential amperage of the wires, by taking a diameter. John Quote Link to post Share on other sites
astontr6 Posted February 4, 2017 Report Share Posted February 4, 2017 John, Following on, on automotive wire, TR6's were built with thick wall PVC Insulation which has a lower amp rating than thin wall PVC. This is due to a different harder grade of PVC compound now used for automotive applications. Another advantage is that it has a slightly higher temp. range and much harder cut through resistance. Bruce. Quote Link to post Share on other sites
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