Fix for the 100amp fuse problem
Discussion
Extra 300 Driver said:
Well today I found that the 100amp fuse had gone. So I replaced it with a circuit breaker, special type ok for high vibration and heat, anyone else done this?
Cost £7.50!!!!
Yeah I did and its never needed reset either so it must be the position the fuse is in that causes it to go.
Sounds like a good idea to me, Maplin have one for £8.00.
www.maplin.co.uk/Module.aspx?ModuleNo=3056&TabID=1&source=1&doy=26m6&ForceUpdate=Y
I expect any serious car audio retailer will have them?
Where did you mount yours?
Bud
www.maplin.co.uk/Module.aspx?ModuleNo=3056&TabID=1&source=1&doy=26m6&ForceUpdate=Y
I expect any serious car audio retailer will have them?
Where did you mount yours?
Bud
I've just asked Maplin a question about their breaker - well two actually!
It looks really good. However we need to know what ambient temperature it is supposed to operate in, and what the principle of operation is. The latter point is important because if it is a thermal breaker, the trip current drops with increasing ambient temperature. The best type to use would be a magneto-hydraulic one (although certainly more expensive).
Personally, it has always struck me as a little odd to use a fuse in this circuit anyway. Not only that, but the alternator is rated at 100 Amp output so I would have expected a larger fuse - say 125 Amp?
When a fuse is run at the rated continuous current then it will heat up considerably, especially when the ambient temperature is fairly high. Maybe this has something to do with the sadly short and unpredictable life of these fuses?
It seems that this fuse tradition is carried over from the Griff/Chim. Land Rover use a fuse too, although the arrangement of the wiring is subtly different. Therefore I think the tradition came with the Land Rover wiring looms on the RV8 engines.
As far as I can make out, in a TVR the fuse carries the full output current of the alternator. In a Land Rover, the fuse carries only the net current between the vehicle (including alternator) and the battery. This is because the output of the alternator goes straight to the vehicle electrical system via a number of large separate fuses.
Overall then, I think I'd lean towards a larger fuse. However I cannot recomment this to anyone since I have not tested it.
It looks really good. However we need to know what ambient temperature it is supposed to operate in, and what the principle of operation is. The latter point is important because if it is a thermal breaker, the trip current drops with increasing ambient temperature. The best type to use would be a magneto-hydraulic one (although certainly more expensive).
Personally, it has always struck me as a little odd to use a fuse in this circuit anyway. Not only that, but the alternator is rated at 100 Amp output so I would have expected a larger fuse - say 125 Amp?
When a fuse is run at the rated continuous current then it will heat up considerably, especially when the ambient temperature is fairly high. Maybe this has something to do with the sadly short and unpredictable life of these fuses?
It seems that this fuse tradition is carried over from the Griff/Chim. Land Rover use a fuse too, although the arrangement of the wiring is subtly different. Therefore I think the tradition came with the Land Rover wiring looms on the RV8 engines.
As far as I can make out, in a TVR the fuse carries the full output current of the alternator. In a Land Rover, the fuse carries only the net current between the vehicle (including alternator) and the battery. This is because the output of the alternator goes straight to the vehicle electrical system via a number of large separate fuses.
Overall then, I think I'd lean towards a larger fuse. However I cannot recomment this to anyone since I have not tested it.
nervous said:
radio reception becomes very poor. do you have this already? if so, bring the car to me and for a nominal sum ill affect a repair.
The rev counter starts to play up first, then the battery doesnt charge.
If I still had the fuse I would carry a spare in the bood, with a few tools.
The reason for the fuse is a safety one. If the alternator should fail s/c it will discharge the battery through the short and this can potentially lead to a fire. It is like arc welding as the battery current will cause things to get very hot indeed.
It also protects the rest of the electrics should the alternator regulator start outputing 15or more volts as the increased current should blow the fuse.
Most of the fuse problems come from bad connections or corrosion because of the location. Also bear in mind the intense heat and vibration that it suffers. That can lead to weakening of the metal fuse as that is exactly the same mechanism that causes the fuse to go anyway. Current induces heat and blows the fuse. The threshold and characteristics of how it is done are also part of the protection as it takes time to melt the fuse and this helps protects against transients caused by switching loads and so on.
It also protects the rest of the electrics should the alternator regulator start outputing 15or more volts as the increased current should blow the fuse.
Most of the fuse problems come from bad connections or corrosion because of the location. Also bear in mind the intense heat and vibration that it suffers. That can lead to weakening of the metal fuse as that is exactly the same mechanism that causes the fuse to go anyway. Current induces heat and blows the fuse. The threshold and characteristics of how it is done are also part of the protection as it takes time to melt the fuse and this helps protects against transients caused by switching loads and so on.
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