john.r.davies Posted February 4, 2017 Report Share Posted February 4, 2017 So TR wires with the same diameter as modern wires/ cables should be rated at less current than modern? John Quote Link to post Share on other sites
GT6M Posted February 4, 2017 Report Share Posted February 4, 2017 Thee,s fuses, and their guide charts are the best ever med, cheep too. M Quote Link to post Share on other sites
astontr6 Posted February 4, 2017 Report Share Posted February 4, 2017 John, Here is an example: Thin Wall: 28/0.30mm, 2mm2 is rated at 25 amps Thick Wall: 28/30mm, 2mm2 is rated at 17.5 amps Bruce Quote Link to post Share on other sites
Prefect Posted February 5, 2017 Report Share Posted February 5, 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
Prefect Posted February 5, 2017 Report Share Posted February 5, 2017 (edited) Have you just rewired the car? Edited February 5, 2017 by Prefect Quote Link to post Share on other sites
RogerH Posted February 5, 2017 Report Share Posted February 5, 2017 Hi John, my only conclusion on the same conductor (cross sectional area) with a thick wall compared to a thin wall having less current ability is that the thick wall keeps the heat in the conductor which in turn will raise its resistance and then become hotter which will raise its resistance etc etc. The modern thin wall is also handy allowing easier fitment in tight spaces. Some of the original bundles are quite unmanageable. Roger Quote Link to post Share on other sites
DaveR Posted February 5, 2017 Report Share Posted February 5, 2017 DC current flows through the whole of the conductor, wire. As far as low voltage DC is concerned its the plain resistance that we have to consider. The larger the conductor the lower its resistance. The higher the current the greater the power lost in the form of heat due to the resistance of the conductor. So if we reduced the resistance by using a larger conductor then we reduce the power loss. The other effect of a high current through a too small cable, to much resistance, will be a voltage drop. In other words as the current requirements increases then the resistance, size, of the conductor becomes important. A higher current requires a bigger conductor. Multi strand cables are used as they withstand vibration and movement much better than one having a single large conductor. In Radio Frequency currents, high frequency AC, things are different - As the frequency increase the current flows more and more on the outer surface of the conductor. This is known as the skin effect. In high power transmitter applications a large hollow conductor is often used to form the coils as most of the current is on the outside of the conductor. Not the case in low voltage DC applications. I'll get my anorak and go. Dave Quote Link to post Share on other sites
RobH Posted February 5, 2017 Report Share Posted February 5, 2017 When selecting fuses remember that the speed at which a fuse blows is related to the degree of overload. A direct short-circuit will draw a very large current far in excess of the fuse rating and this will blow the fuse almost immediately so the current will not flow for long. A small overload of a few extra amps may take minutes to heat the fuse element sufficiently for it to fail and during all that time the wires carrying the current are getting warmer than they should, to the detriment of the insulation. Its also worth noting that the current rating of a cable is quoted for free-air. If its bundled up in a loom, perhaps with further insulation wrap, it should be de-rated as the temperature will be higher. Quote Link to post Share on other sites
DaveR Posted February 5, 2017 Report Share Posted February 5, 2017 When selecting fuses remember that the speed at which a fuse blows is related to the degree of overload. A direct short-circuit will draw a very large current far in excess of the fuse rating and this will blow the fuse almost immediately so the current will not flow for long. A small overload of a few extra amps may take minutes to heat the fuse element sufficiently for it to fail and during all that time the wires carrying the current are getting warmer than they should, to the detriment of the insulation. Its also worth noting that the current rating of a cable is quoted for free-air. If its bundled up in a loom, perhaps with further insulation wrap, it should be de-rated as the temperature will be higher. Rob, brings back memories of a Wireless Mec running an electric fire through not full unreeled 13 Amp lead-line! Dave Quote Link to post Share on other sites
RobH Posted February 5, 2017 Report Share Posted February 5, 2017 Two fires for the price of one?? Quote Link to post Share on other sites
DaveR Posted February 5, 2017 Report Share Posted February 5, 2017 Melted the reel. To be fair there was nothing on the reel in those days about only using it when reeled out. Training issue. Dave Quote Link to post Share on other sites
Mike Atwell Posted February 6, 2017 Report Share Posted February 6, 2017 Hi Prefect, No I have not. Quote Link to post Share on other sites
matttnz Posted February 6, 2017 Report Share Posted February 6, 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? The green red wire runs from the Master lighting switch to the fusebox, then red to front side lamps & dash lights. Your ML switch must be set to the 1st setting, broken or incorrectly wired Quote Link to post Share on other sites
peejay4A Posted February 6, 2017 Report Share Posted February 6, 2017 ...and what about the lighting switch as suggested by me in post 21 and Matt above? Quote Link to post Share on other sites
Mike Atwell Posted February 6, 2017 Report Share Posted February 6, 2017 I have just been told that I have been "bombing" other people's posts. I was not not aware that I have, but if I have, I apologise profusely. Please explain the correct procedure for asking questions Quote Link to post Share on other sites
RogerH Posted February 6, 2017 Report Share Posted February 6, 2017 Hi Mike, not sure what bombing is but all fine by me. Roger Quote Link to post Share on other sites
john.r.davies Posted February 6, 2017 Report Share Posted February 6, 2017 The Master has spoken. I'd say that a strictly relevant Q is OK, but if its a spin off, start a new thread. If you like, copy the address of the thread to show where you are coming from Quote Link to post Share on other sites
Mike Atwell Posted February 6, 2017 Report Share Posted February 6, 2017 This is what I received. Prefect, on 05 Feb 2017 - 5:31 PM, said: Hi MikeIt looks like you bombed someone else post that's why you have no replies!Are you sure your light switch is OFF?Pete Hi, I am really sorry, I did not mean to "bomb" anyone's posts. What did I do that was wrong? Yes, the light switch is off Reply Report Edit Quote Link to post Share on other sites
peejay4A Posted February 6, 2017 Report Share Posted February 6, 2017 (edited) OK. Remove the green/red wire which should be the feed from the lighting switch. Do the lights stay on? Is there 12v on the red wires? If yes then you've incorrectly replaced the wires on the fuse box or the fuse box is different to the original. Better still can you post a picture showing the fuse box wiring arrangement? Edited February 6, 2017 by peejay4A Quote Link to post Share on other sites
RogerH Posted February 6, 2017 Report Share Posted February 6, 2017 Hi Mike, you have a PM - Red envelope top right hand corner. Roger Quote Link to post Share on other sites
Mike Atwell Posted February 6, 2017 Report Share Posted February 6, 2017 (edited) Here is what caused my problem with the side lights. I bought a new fusebox and installed it without looking at the back. The new one has two terminals bridged. See picture. Old one on left Edited February 6, 2017 by Mike Atwell Quote Link to post Share on other sites
RogerH Posted February 6, 2017 Report Share Posted February 6, 2017 Well found Mike. That could have given you a few sleepless nights. Where did you get the fuse box and was it specified for your car? Roger Quote Link to post Share on other sites
stuart Posted February 6, 2017 Report Share Posted February 6, 2017 This is what I received. Prefect, on 05 Feb 2017 - 5:31 PM, said: Hi, I am really sorry, I did not mean to "bomb" anyone's posts. What did I do that was wrong? Yes, the light switch is off Reply Report Edit You didnt do anything wrong and that message was very unnecessary by the looks of it. Old threads are very often brought back to life when someone has a similar problem. Stuart. Quote Link to post Share on other sites
peejay4A Posted February 6, 2017 Report Share Posted February 6, 2017 Ahem. ;-) Quote Link to post Share on other sites
matttnz Posted February 7, 2017 Report Share Posted February 7, 2017 I have just been told that I have been "bombing" other people's posts. I was not not aware that I have, but if I have, I apologise profusely. Please explain the correct procedure for asking questions A hanging offence for some, not a major issue for others but given the lack of manners on many forums it's easier (safer?) to be fastidious in the rules. I've not seen bad behaviour on the TR register before though! Can't imagine this place attracts many trolls. Refers to adding a question that deviates the thread into a different direction. it would be better to construct a new thread with your question separately. Often the forum moderators will do this as a "tidy up" in many forums. MT Quote Link to post Share on other sites
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