Wiring a master cut out switch?
Discussion
The diagram that came with the switch shows the big main terminals for cutting the battery lead, ie the main electrical feed.
You then have 2 sets of spade connectors. One of which cuts between the coil and ignition switch.
Now for the bit i dont understand: The remaining terminals are shown as switching between the main electrical feed and earth, via a 3ohm resister. ie the electrical feed from the little spade termial is branched off the electrical feed from the large battery cable terminals.
How should this last bit be wired up?
You then have 2 sets of spade connectors. One of which cuts between the coil and ignition switch.
Now for the bit i dont understand: The remaining terminals are shown as switching between the main electrical feed and earth, via a 3ohm resister. ie the electrical feed from the little spade termial is branched off the electrical feed from the large battery cable terminals.
How should this last bit be wired up?
Found this copy of the wiring diagram: http://www.dazecoop.co.uk/15-06-2006/wiring-batter...
So the terminal to the resistor opens when the switch is thrown, got that now.
On a mini there are 3 connections to the alternator, the smaller terminal going to the charging light. Which of the other 2 is the main feed to the alternator which needs to go through this switch to the resistor? Or is there a connection nearer the bulkhead that can be wired into?
So the terminal to the resistor opens when the switch is thrown, got that now.
On a mini there are 3 connections to the alternator, the smaller terminal going to the charging light. Which of the other 2 is the main feed to the alternator which needs to go through this switch to the resistor? Or is there a connection nearer the bulkhead that can be wired into?
the big ring terminal on the cut out switch that is labeled "main electrical feed circuit" on the diagram is where you wire the resistor to, very short wire run!
dont forget that in the event of the cut out switch being activated at high reves, the resistor is taking the charge the slowing alternator is producing, it will get hot so place it carefully, also with a long wire run that goes directly to the alternator, the wire could melt, keep it short simple and all together on the cut out switch if you can!
this is how mine was wired and it passed the msa inspection/scrutineering ok on the last 3 cars i wired up!
dont forget that in the event of the cut out switch being activated at high reves, the resistor is taking the charge the slowing alternator is producing, it will get hot so place it carefully, also with a long wire run that goes directly to the alternator, the wire could melt, keep it short simple and all together on the cut out switch if you can!
this is how mine was wired and it passed the msa inspection/scrutineering ok on the last 3 cars i wired up!
haynes said:
Does that mean you put a short thin wire from the big battery cable size connection straight down to the little spade terminal?
Yes, and then on through the resistor to earth.Make sure you do connect to the engine side of the main cable though... if you connect the battery side, first time you switch it off you'll flatten the battery through the resistor! Not a good idea !!
A bit more practical advise please.
Is 1.5mm wire with crimps man enough to link between the battery terminal and terminal 1? (I suppose the battery cable is only so thick to cope with the load from of starter motor?)
How do you actually mount the resistor. Does it need to be strapped down or are the legs sufficient to support it? I would normally think about wrapping a cable tie around it but would the heat be too much?
Is 1.5mm wire with crimps man enough to link between the battery terminal and terminal 1? (I suppose the battery cable is only so thick to cope with the load from of starter motor?)
How do you actually mount the resistor. Does it need to be strapped down or are the legs sufficient to support it? I would normally think about wrapping a cable tie around it but would the heat be too much?
Personally I'd use 28/030 wire (2mm*)although even that is in theory undersize.
The current that can flow through the resistor is equivalent to the max output of the alternator BUT that will only occour when you operate the switch with the engine at high revs and only for the length of time it takes the engine to stop.
So although the wire (and resistor) will heat up it's only for a second or so and hopefully not too often.
I would also mount the resistor solidly, mainly to stop it flapping about and breaking the wires.
There are a couple of different types - if it has a metal heatsink it's quite easy to bolt down, if it's the ceramic type you'll have to make something up! A metal strap maybe? although a couple of cable ties would probably be sufficient.
It's not really a good idea to use the switch to stop the engine on a regular basis although of course as with any safety eq. you should test it every now and then.
The current that can flow through the resistor is equivalent to the max output of the alternator BUT that will only occour when you operate the switch with the engine at high revs and only for the length of time it takes the engine to stop.
So although the wire (and resistor) will heat up it's only for a second or so and hopefully not too often.
I would also mount the resistor solidly, mainly to stop it flapping about and breaking the wires.
There are a couple of different types - if it has a metal heatsink it's quite easy to bolt down, if it's the ceramic type you'll have to make something up! A metal strap maybe? although a couple of cable ties would probably be sufficient.
It's not really a good idea to use the switch to stop the engine on a regular basis although of course as with any safety eq. you should test it every now and then.
Thanks Dino. The switch came with a ceramic type. Ive just bought a new alternator so really dont want to blow it, but yes this switch wont be used to switch the engine off under normal circumstances but want to get it right. Atcually, this thick bit of brown wire from an old loom i had in mind to use is 2mm.
That sounds fine.
You won't blow the alternator, the worst that will happen is the wire and resistor will get warm, just make sure there's some air around them and it'll be fine.
I reuse wire from old looms as well, just make sure it's not damaged or tarnished and you get a good clean crimp.
You won't blow the alternator, the worst that will happen is the wire and resistor will get warm, just make sure there's some air around them and it'll be fine.
I reuse wire from old looms as well, just make sure it's not damaged or tarnished and you get a good clean crimp.
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