Mod-wise Live Feed for Cooling Kit
Discussion
Dear All,
I've recently fitted the Mod-wise hot start and coolng fan kits and both were really easy to do. The cooling kit I bought also has the ignition-off run on for the fans which requires a live feed.
I searched the forum and some people also have the same kit. But they don't say how they've run this wire from the starter +ve terminal to the relay kit at the front. Any siggestions? My concern is the heat from the exhaust manifold. Will this cause problems for the wire insulation e.g. melt it?
Is it possible to run this live feed from the battery by going through one of the gromits in the bulk head, assuming one can get to and through it.
Many thanks in advance
Kim
I've recently fitted the Mod-wise hot start and coolng fan kits and both were really easy to do. The cooling kit I bought also has the ignition-off run on for the fans which requires a live feed.
I searched the forum and some people also have the same kit. But they don't say how they've run this wire from the starter +ve terminal to the relay kit at the front. Any siggestions? My concern is the heat from the exhaust manifold. Will this cause problems for the wire insulation e.g. melt it?
Is it possible to run this live feed from the battery by going through one of the gromits in the bulk head, assuming one can get to and through it.
Many thanks in advance
Kim
On a Griff mind, but I drilled a small hole(approx 8mm) in the fibreglass above the rad so the cable comes through here over the top of the rad, feeds through by where the horn is located and along the bottom chassis rail. The cable is inside a corrugated sheath and cable tied to the chassis.
FFG
FFG
I connected a live feed for an alternative cooling fan solution to the alternator +ve. I managed to find a nice rubberised fuse holder from Halfords which I put into the first 150mm of the wire.
I'm an electrical engineer who at one time used to be responsible for alternator testing at Lucas so I'm absolutely confident that this is OK.
Mike
I'm an electrical engineer who at one time used to be responsible for alternator testing at Lucas so I'm absolutely confident that this is OK.
Mike
miketvr said:
I'm an electrical engineer who at one time used to be responsible for alternator testing at Lucas so I'm absolutely confident that this is OK.
[offtopic]
Mike, what's your opinion on the 100 Amp Fuse? Can it be removed? Any reason why it shouldn't be moved into the engine bay?
[/offtopic]
Edited by theaxe on Wednesday 1st November 08:55
My view on the 100A fuse has been aired here before: it appears to create more problems than it solves and it isn't fitted to all cars which would tend to suggest it isn't strictly necessary. However, it must also have been fitted for a reason. As it isolates the alternator's output from the rest of the car's electrical systems, either it protects those systems from the alternator or it protects the alternator from those systems. For the fuse to melt (or 'blow') it would have to carry more than 100A towards, or away from, the alternator. Let's examine a few scenarios:
1. A short circuit develops somewhere in the vehicle's wiring. All circuits within the vehicle are protected by a lower-rated fuse which would thoretically fail before the 100A fuse, except the starter motor supply which is not fused. So, if a short-circuit developed here whilst the engine was running (and the alternator producing output), the 100A fuse would fail, so protecting the alternator. This would make the fuse worthwhile: the battery would of course fail, hopefully averting a fire. (The actual supplies to the fusebox are probably not protected either: correct me if this is wrong!).
2. A fault develops in the alternator, causing it to produce an over-current. Assuming no other faults within the electrical system this could only happen if the alternator started producing a much higher voltage than normal. Such a fault could damage both the alternator and ANY other electrical system, from the wiring loom itself, to simple bulbs, to more expensive and vulnerable equipment such as the fuel injection ECU. The 100A fuse would melt, the current would cease and all systems including the alternator would be protected.
3. A short circuit develops in the alternator. The battery would provide a current through this path which would melt the 100A fuse once the current reached 100A. This would protect the battery and the wiring between it and the alternator.
This covers most scenarios in which the 100A fuse could offer protection. But, if you fitted an alternative cooling fan circuit as in this thread and you took its feed from the line between the 100A fuse and the alternator, it could reduce the effectiveness of the 100A fuse. How? Well, imagine the alternator is producing an 80A charging output back to the battery, then you switch on the new cooling fan circuit, drawing, say, 30A. The alternator output could rise to 110A (10A beyond its rating and potentially damaging it) without the 100A fuse melting, as it is only carrying 80A. For this reason, I would not connect the new fan feed directly to the back of the alternator. You should remember though, that in reality such a scenario might not arise: the fans might not draw 30A (except at start-up) and the alternator may well not be producing a continuous 80A charging current, but nevertheless it is a possibility.
1. A short circuit develops somewhere in the vehicle's wiring. All circuits within the vehicle are protected by a lower-rated fuse which would thoretically fail before the 100A fuse, except the starter motor supply which is not fused. So, if a short-circuit developed here whilst the engine was running (and the alternator producing output), the 100A fuse would fail, so protecting the alternator. This would make the fuse worthwhile: the battery would of course fail, hopefully averting a fire. (The actual supplies to the fusebox are probably not protected either: correct me if this is wrong!).
2. A fault develops in the alternator, causing it to produce an over-current. Assuming no other faults within the electrical system this could only happen if the alternator started producing a much higher voltage than normal. Such a fault could damage both the alternator and ANY other electrical system, from the wiring loom itself, to simple bulbs, to more expensive and vulnerable equipment such as the fuel injection ECU. The 100A fuse would melt, the current would cease and all systems including the alternator would be protected.
3. A short circuit develops in the alternator. The battery would provide a current through this path which would melt the 100A fuse once the current reached 100A. This would protect the battery and the wiring between it and the alternator.
This covers most scenarios in which the 100A fuse could offer protection. But, if you fitted an alternative cooling fan circuit as in this thread and you took its feed from the line between the 100A fuse and the alternator, it could reduce the effectiveness of the 100A fuse. How? Well, imagine the alternator is producing an 80A charging output back to the battery, then you switch on the new cooling fan circuit, drawing, say, 30A. The alternator output could rise to 110A (10A beyond its rating and potentially damaging it) without the 100A fuse melting, as it is only carrying 80A. For this reason, I would not connect the new fan feed directly to the back of the alternator. You should remember though, that in reality such a scenario might not arise: the fans might not draw 30A (except at start-up) and the alternator may well not be producing a continuous 80A charging current, but nevertheless it is a possibility.
In response to Cider Andy's post.
An alternator doesn't overload, it simply runs out of steam and folds back voltage to give the maximum current it can. Hence it cannot damage in this way.
A 100 Amp fuse will probably take about a day and a half to rupture at 110A. Fuses of this type are usually rated to blow quickly at considerably higher currents.
I did say that I added a separate fuse in the first 150mm of the cable which would protect everything else from the fan circuit.
In response to the earlier question of what do I think about the 100 Amp fuse ?
I don't have one on my 94 Chim so I'm not absolutely sure where it comes in the circuit. If it's in the alternator line only then I would think that it's been put in in response to rectifier failures in the alternator which can draw a lot of battery current to ground. If a battery is subject to massive discharge it can gas and cause the battery to explode. As the battery is inside the car it would not be a happy situation and could be the primary reason for TVR spending money on a safety device. I knew someone who dropped a spanner on to the terminals of a battery which immediately blew the battery to a million pieces and landed him in hospital with considerable acid burns to his face. Luckily he was wearing glasses.
Mike
An alternator doesn't overload, it simply runs out of steam and folds back voltage to give the maximum current it can. Hence it cannot damage in this way.
A 100 Amp fuse will probably take about a day and a half to rupture at 110A. Fuses of this type are usually rated to blow quickly at considerably higher currents.
I did say that I added a separate fuse in the first 150mm of the cable which would protect everything else from the fan circuit.
In response to the earlier question of what do I think about the 100 Amp fuse ?
I don't have one on my 94 Chim so I'm not absolutely sure where it comes in the circuit. If it's in the alternator line only then I would think that it's been put in in response to rectifier failures in the alternator which can draw a lot of battery current to ground. If a battery is subject to massive discharge it can gas and cause the battery to explode. As the battery is inside the car it would not be a happy situation and could be the primary reason for TVR spending money on a safety device. I knew someone who dropped a spanner on to the terminals of a battery which immediately blew the battery to a million pieces and landed him in hospital with considerable acid burns to his face. Luckily he was wearing glasses.
Mike
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