Ready to fit my fuse 22 switch as per julian1963's method
Discussion
Have one question. There is a 20 amp fuse in the fuse 22 location but does the circuit actually draw 20 amps? It is difficult to find 20 amp switches, so my choises are find one or use a relay in the circuit, unless the fuse 22 circuit doesn't really draw 20 amps in which case I could use a 16 amp switch and not use a relay.
BingoBob said:
Have you got a multimeter that you can measure the current draw with? I personally can't believe that it will pull anywhere near that.
I have. Do I just need to rev past 1500 RPM to get the vacuum to operate? I believe the valves are open between 0-1500 RPM, closed between 1500-4000 and then open again after 4000 RPM, so I just need to rev past 1500 RPM to get the circuit to operate.Couple of things
Julian's method looks to be good providing that the fuse is protecting the switch and cable and not the other way round.
With the unidentified blades it is quite possible for the supply voltage to exit the fusebox, go to the switch down the piece of cable, return to the fuse and then on to the exhaust solenoid. If the cable becomes damaged then you have bypassed the fuse and all bets are off as to what the outcome is.
Conversely install the blades the other way round and the fuse continues to protect the wiring to the switch, the switch and the existing solenoid and wiring. I'm assuming that the intention is that the fuse remains in the fuse box and is physically protected in there.
With regards to the 20amp rating...... Many DVMs will not cope with 20amps so check carefully before you destroy (or blow the fuse in) your DVM.
If you don't believe it draws 20amps, pop a 10 amp fuse in and see how long it lasts. If it works for a few weeks of repeated use derate the fuse to that value and you can safely use a derated switch. I would not recommend derating the switch without derating the fuse.
My 2p
Julian's method looks to be good providing that the fuse is protecting the switch and cable and not the other way round.
With the unidentified blades it is quite possible for the supply voltage to exit the fusebox, go to the switch down the piece of cable, return to the fuse and then on to the exhaust solenoid. If the cable becomes damaged then you have bypassed the fuse and all bets are off as to what the outcome is.
Conversely install the blades the other way round and the fuse continues to protect the wiring to the switch, the switch and the existing solenoid and wiring. I'm assuming that the intention is that the fuse remains in the fuse box and is physically protected in there.
With regards to the 20amp rating...... Many DVMs will not cope with 20amps so check carefully before you destroy (or blow the fuse in) your DVM.
If you don't believe it draws 20amps, pop a 10 amp fuse in and see how long it lasts. If it works for a few weeks of repeated use derate the fuse to that value and you can safely use a derated switch. I would not recommend derating the switch without derating the fuse.
My 2p
Not sure I understand. With fuse 22 in, the vacuum operates between 1500-4000rpm to close the valves in the exhausts. At 0-1500 and over 4000 RPM the vacuum is not operating. So when I removed fuse 222 I have made the vacuumm not operating at all.
In the circuit that julian1963 has used, the 20 amp fuse remains in the circuit so the circuit cannot be closed without current flowing through the fuse, so the wiring and switch are protected by the fuse.
I am not sure I understand when you said it could be the other way around and that the switch and wiring could be protecting the fuse (which would of course be far from ideal). Are you saying that the spades have to be inserted in the fuse 22 location in the fuse box so that the current flows through the fuse in the circuit first?
In the circuit that julian1963 has used, the 20 amp fuse remains in the circuit so the circuit cannot be closed without current flowing through the fuse, so the wiring and switch are protected by the fuse.
I am not sure I understand when you said it could be the other way around and that the switch and wiring could be protecting the fuse (which would of course be far from ideal). Are you saying that the spades have to be inserted in the fuse 22 location in the fuse box so that the current flows through the fuse in the circuit first?
Edited by v8woollie on Tuesday 3rd April 14:18
v8woollie said:
I am not sure I understand when you said it could be the other way around and that the switch and wiring could be protecting the fuse (which would of course be far from ideal). Are you saying that the spades have to be inserted in the fuse 22 location in the fuse box so that the current flows through the fuse in the circuit first?
If my understanding is correct the circuit will behave in a "survival of the fittest" kind of logic. So the component least able to carry the current will fail first in the event of a current spike.EG. If the fuse is rated at 20A but the switch only 10A ... then the instant the the current spikes past 10A, the switch will break and the circuit will be broken before the fuse is blown. That's why in an ideal world the other components should all be rated as high as or higher than the fuse.
Edited by RIB27 on Tuesday 3rd April 14:53
RIB27 said:
If my understanding is correct the circuit will behave in a "survival of the fittest" kind of logic. So the component least able to carry the current will fail first in the event of a current spike.
EG. If the fuse is rated at 20A but the switch only 10A ... then the instant the the current spikes past 10A, the switch will break and the circuit will be broken before the fuse is blown. That's why in an ideal world the other components should all be rated as high as or higher than the fuse.
Ah OK. I did overspec things to be safe. I have 30 amp wire, a waterproof fuse folder with 30 amp wire and a 20 amp switch so I hope I am good to go EG. If the fuse is rated at 20A but the switch only 10A ... then the instant the the current spikes past 10A, the switch will break and the circuit will be broken before the fuse is blown. That's why in an ideal world the other components should all be rated as high as or higher than the fuse.
I am infact wiring it as in your diagram in the other fuse 22 thread:
http://thumbsnap.com/cdx1FYjG
Edited by v8woollie on Tuesday 3rd April 14:55
v8woollie said:
Ah OK. I did overspec things to be safe. I have 30 amp wire, a waterproof fuse folder with 30 amp wire and a 20 amp switch so I hope I am good to go
That will be more than adequate. The most important thing is that the circuit is fused at some point - other than that you can't go too far wrong 
RIB27 said:
That will be more than adequate. The most important thing is that the circuit is fused at some point - other than that you can't go too far wrong
Thanks.Does it matter which way round the spades go into the fuse box? Also, I bought standard male and female spade connectors. Do these need to be 20 amp or are standard ones OK?
v8woollie said:
Does it matter which way round the spades go into the fuse box? Also, I bought standard male and female spade connectors. Do these need to be 20 amp or are standard ones OK?
I lifted the below from another forum:Red: 19A
Blue: 27A
Yellow: 48A
Your spades will most likely be absolutely fine.
Edited by RIB27 on Tuesday 3rd April 17:43
I purchased these:
http://www.maplin.co.uk/insulated-crimp-terminal-l...
and the spec states:
ML82D Yellow 23mm 12A 2.5-6.5mm
No good?
http://www.maplin.co.uk/insulated-crimp-terminal-l...
and the spec states:
ML82D Yellow 23mm 12A 2.5-6.5mm
No good?
You should not run that current to a switch! Use a common relay, maybe 2-3 pounds. I just ran the ground wire to the switch, in my case I put the switch were the cigar lighter would be under the little trap door. I put the relay right next to the fuse box ran power from the spades on the fuse holder to the relay. I only took a few minutes running the wire into the cabin was the hardest part.
millsjq said:
You should not run that current to a switch! Use a common relay, maybe 2-3 pounds. I just ran the ground wire to the switch, in my case I put the switch were the cigar lighter would be under the little trap door. I put the relay right next to the fuse box ran power from the spades on the fuse holder to the relay. I only took a few minutes running the wire into the cabin was the hardest part.
Any chance of a diagram to show how to wire the fusebox to the relay to the switch?millsjq said:
You should not run that current to a switch! Use a common relay, maybe 2-3 pounds. I just ran the ground wire to the switch, in my case I put the switch were the cigar lighter would be under the little trap door. I put the relay right next to the fuse box ran power from the spades on the fuse holder to the relay. I only took a few minutes running the wire into the cabin was the hardest part.
Here's a thread where somebody has used a relay in the system - http://www.pistonheads.com/gassing/topic.asp?h=0&a...This is popular if you want to put the switch inside the cabin as running long wires with the fuse and switch inline is not so ideal. In my experience I've seen people using a range of methods from the simple inline fuse + switch suggested by julian1963 (as I do), to combined fuses/switches, to hardwired relays, to remote relay switches. It comes down to your requirements and what you're comfortable with doing on your car.
As mentioned by others there are some neat off the shelf options out there too.
Edited by RIB27 on Tuesday 3rd April 16:00
The reason I want to switch at will is that I live in a quiet residential area and don't want to make a racket at 6:30 in the morning or late at night. I also prefer it a little quieter when cruisng down the motorway. At 80mph and 3000 RPM for a couple of hours it would be nice to have the exhausts quieten down and therefore be less fatiguing.
I therefore want a switch in the cabin (on the rear shelf is fine) rather than have to stop and get into the boot.
I therefore want a switch in the cabin (on the rear shelf is fine) rather than have to stop and get into the boot.
shunt said:
For those unsure what they are doing I would recommend spending £100 on a Paralight remote switch. Trust me I'm an engineer!
If this Paralight unit is the same as the Maplins one that has been linked to in another thread, it says it switches up to 12A. Is it a good idea to have this in a 20 amp circuit?Gassing Station | Aston Martin | Top of Page | What's New | My Stuff