Electrical circuit live ONLY when engine running

Andy Harvey

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Mar 6, 2010
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Anyone help with this - had a look with Julian V and we came up with terminal L on the Alternator, however this is a PITA to get at on the 1HD-FTE. Does anyone know of a pickup point for a circuit that only comes live when the engine is running - either on an accessible connector block or at the ECU maybe.

I need this to feed the control relay for my HHO (Hydrogen) kit I'm installing - have everythin put in apart from this. It needs to be live only when the engine is running due to the fact you don't want to be generating Hydrogen when the engine isn't running - I could put it on a switch but to be honest there is too much chance of either leaving it on or forgetting to switch it on. I will will also be putting a disable switch into the circuit when I find where to take the feed from just in case it gets cold and the thing ices up.

Any help much appreciated - getting at the alternator wiring is an utter nightmare.

Another possibility may be to take a feed from the AHC ECU as I know this only operates when the engine is running so it must have a feed I could tap off soemwhere I guess.

Vehicle is 1999 100 Series VX Diesel
 

Gary Stockton

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Off the cigarette lighter or similar? - I assume you want to hook it up in the engine bay, so you'd have to back out the firewall ... not sure what else is in the main fuse box....
 

Andy Harvey

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Gary.

No it needs to be only when the engine is running - the cigarette lighter is live when the ignition is on whether the engine is running or not. Problem with that is that I could be sitting with the ignition on and producing Hydrogen even though the engine is running - then there could be a build up of the gas which you definately don't want.
 

Crispin

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Why not use a couple of small relays off the oil pressure light and ignition. One latching one off the starter, one NO contact off the oil light. Starter causes one to latch, when the oil light comes on (stalled) or lack of ignition, the relay drops out.

Maybe simpler would be a voltage sensing relay used to charge a caravan battery? The battery will be over 13V when the engine is running. When the engine is off, the relay should drop out.
 
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Gary Stockton

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Yep - like that idea with the relay - that should help - and it will only fire up when the truck is running ... :lol: (scuze the pun ....)
 

Andy Harvey

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Jon.

Will have a look at the fuel shut off relay idea - didn't think of that - think they do but will check.

Not sure if the Hydrogen kit is Snake Oil, will see when I have it running - the idea certainly makes sense and some magazines have covered them and say they work so we'll see. On the extra economy side I'm not after much - would like maybe to get the average on a run over 30mpg - currently about 26 - 27 (could probably do better but haven't got bored with the extra power over the 80 so I still tend to drive it a lot like I stole it :lol: :lol:
 

Steve Wright

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Andy Harvey said:
Anyone help with this - had a look with Julian V and we came up with terminal L on the Alternator, however this is a PITA to get at on the 1HD-FTE. Does anyone know of a pickup point for a circuit that only comes live when the engine is running - either on an accessible connector block or at the ECU maybe.

I need this to feed the control relay for my HHO (Hydrogen) kit I'm installing - have everythin put in apart from this. It needs to be live only when the engine is running due to the fact you don't want to be generating Hydrogen when the engine isn't running - I could put it on a switch but to be honest there is too much chance of either leaving it on or forgetting to switch it on. I will will also be putting a disable switch into the circuit when I find where to take the feed from just in case it gets cold and the thing ices up.

Any help much appreciated - getting at the alternator wiring is an utter nightmare.

Another possibility may be to take a feed from the AHC ECU as I know this only operates when the engine is running so it must have a feed I could tap off soemwhere I guess.

Vehicle is 1999 100 Series VX Diesel
Hi Andy

If non of the other suggestions work, the easiest way to get a live supply only when the engine is running, is the way we used to wire what was called a split relay for charging a battery !

you need a cheap relay, with four connections, then find the wire on the alternator that goes to the IGN warning light on the dash, (it will be a very thin wire) that comes off the terminal block on the Alternator,

Connector 85 = chassis earth (one side of the coil)
Connector 86 = operating the relay (Thin wire on alternator)
Connector 87 = Live feed from battery (via a fuse)
Connector 30 = then take this wire to your device.

So when the ign is off and also when the Ign light is on, there is no voltage to the relay, but as soon as the IGN light goes off then the relay energizes so switches on the device, and as soon as the engine stops, the device switches off.
 

Andy Harvey

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Mar 6, 2010
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Steve Wright said:
[quote="Andy Harvey":1ve7zw5x]Anyone help with this - had a look with Julian V and we came up with terminal L on the Alternator, however this is a PITA to get at on the 1HD-FTE. Does anyone know of a pickup point for a circuit that only comes live when the engine is running - either on an accessible connector block or at the ECU maybe.

I need this to feed the control relay for my HHO (Hydrogen) kit I'm installing - have everythin put in apart from this. It needs to be live only when the engine is running due to the fact you don't want to be generating Hydrogen when the engine isn't running - I could put it on a switch but to be honest there is too much chance of either leaving it on or forgetting to switch it on. I will will also be putting a disable switch into the circuit when I find where to take the feed from just in case it gets cold and the thing ices up.

Any help much appreciated - getting at the alternator wiring is an utter nightmare.

Another possibility may be to take a feed from the AHC ECU as I know this only operates when the engine is running so it must have a feed I could tap off soemwhere I guess.

Vehicle is 1999 100 Series VX Diesel
Hi Andy

If non of the other suggestions work, the easiest way to get a live supply only when the engine is running, is the way we used to wire what was called a split relay for charging a battery !

you need a cheap relay, with four connections, then find the wire on the alternator that goes to the IGN warning light on the dash, (it will be a very thin wire) that comes off the terminal block on the Alternator,

Connector 85 = chassis earth (one side of the coil)
Connector 86 = operating the relay (Thin wire on alternator)
Connector 87 = Live feed from battery (via a fuse)
Connector 30 = then take this wire to your device.

So when the ign is off and also when the Ign light is on, there is no voltage to the relay, but as soon as the IGN light goes off then the relay energizes so switches on the device, and as soon as the engine stops, the device switches off.[/quote:1ve7zw5x]

Steve.

Thanks, actually have the relay so that is no problem - have a standard 4 connection relay. My only problem is getting to that connection on the back of the Alternator easily. I think the one you are saying is the L connection. Problem on the 1HD-FTE is the Alternator is stuck down underneath the Aircon pump and stuck behind all the pipes for the Intercooler so it is a real bugger to get at - I'm kind of spending as little time on this as possible as my Wife is in hospital and I am up there visiting quite a bit of the time. I'm hoping someone knows where this wire comes out in a connector that is a little more accessible - the way to get at the alternator on mine is either through the bottom after removing the underpand an a host of other gubbins, or take out the airbox, the intercooler hoses, lift up the aircon pump and there you have it - a long time later you can get a connection on the back of the alternator. But if I can't find anything else then I guess that is going to be the way I have to go.

Thanks for the help though Steve, at least that confirms the Alternator connection we are talking about.
 

Andy Harvey

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Mar 6, 2010
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Cheltenham, UK
Jon Wildsmith said:
Do the 1HD-FTE's have a fuel shut off solenoid like the 80 series? I would tap into the circuit if they do.

A voltage sense device will tend to stay on for a bit after the engine stops.
Jon.

Just checked, the FTE doesn't have a Fuel shutoff valve unlike the 1HD-T and FT. Looks like the alternator route is going to be the one I have to go with. As they say in that Aussie Hilux advert - Bugga!!
 

Jon Wildsmith

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Andy Harvey said:
Just checked, the FTE doesn't have a Fuel shutoff valve unlike the 1HD-T and FT. Looks like the alternator route is going to be the one I have to go with. As they say in that Aussie Hilux advert - Bugga!!
Bugga indeed, maybe the other end of the alternator wire is easier to get at behind the dash.
 

Henri Stofberg

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I didn't read through the whole thing but I needed something similar on my dual battery setup.

Use a 5 pin relay and trigger it from the alternator light. So when the ignition is on, no power. When the engine runs, no alternator light, thus power.
 

Andy Harvey

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Mar 6, 2010
343
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Cheltenham, UK
Yep I think that I'm gonna find out the colour code for the wire going into the multi plug on the back of the instruments rather than spending all that time ripping apart the engine bay to get at the alternator plug - I'm glad my LC has a new Alternator (it went 2 years ago when my mate had it). Hopefully shold be easier to find and at least the instruments are easy to get out (although the plugs are semi fixed to the dash so that makes it a bit more interesting.
 

Andy Harvey

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Mar 6, 2010
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Cheltenham, UK
OK.

Done some more research and the altentaor / ignition warning light feed is the way to go. Reason for this is as follows for anyone who wants to know.

1. When Ignition is on, the alternator is providing no charge, the ignition light is fed from a battery positive on one side and gets an earth from the alternator because there is no charge. This means that on the alternator side of the ignition light there will be an earth so no battery voltage to switch the relay.
2. When engine is running, the alternator is providing a charge so provides a positive voltage up the feed to the igintion light which meets the positive voltage on the other side and so the bulb goes out - it cannot get to earth to complete the circuit. However now we have a positive voltage on the alternator side of the indicator lamp and this goes to earth through the relay and switches the relay.

Hooray I understand it now. Also useful understanding for why it works this way for split charging relays.
 

Steve Wright

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Andy Harvey said:
OK.

Done some more research and the altentaor / ignition warning light feed is the way to go. Reason for this is as follows for anyone who wants to know.

1. When Ignition is on, the alternator is providing no charge, the ignition light is fed from a battery positive on one side and gets an earth from the alternator because there is no charge. This means that on the alternator side of the ignition light there will be an earth so no battery voltage to switch the relay.
2. When engine is running, the alternator is providing a charge so provides a positive voltage up the feed to the igintion light which meets the positive voltage on the other side and so the bulb goes out - it cannot get to earth to complete the circuit. However now we have a positive voltage on the alternator side of the indicator lamp and this goes to earth through the relay and switches the relay.

Hooray I understand it now. Also useful understanding for why it works this way for split charging relays.
Hi Andy

Glad you have sussed it, I know what I am doing but I find it hard to explain in text what I mean !

But as you know that you get 12 volts at one side of the IGN light, and uses the other wire at the Alternator as earth until
it starts charging, the only problem if you take the wire for the coil, make sure you have the correct wire, as if you check with a multimeter you will get 12 volts on both sides of the lamp !

There is another way to do it, but a little more expensive, and its called a "smartcom" again used for caravan battery charging and running the fridge , and works on the rise in voltage, as it goes from 12 volts to 13.8 or more, then it switches a relay, works very well and can be wired in any where in the circuit, so could be easer for you.
 

Andy Harvey

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Mar 6, 2010
343
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Cheltenham, UK
OK for anyone else who needs to know, I have now found the little bugga. On the back of the guage cluster there are 4 connectors. The one nearest the door is in the manual called Connector 12 but is labelled on the back of the guage cluster is called CNA. On the block soldered to the cluster there are numbers, you need pin 10. Now you need to go to the plug which is still on the vehicle (rather than the socket on the cluster) and find the corresponding pin on that plug. Check once, twice and then again because it can be awkward making sure you have the right one as you are looking at it from a different angle (the socket on the cluster when you are looking at the back of the cluster is on the left hand side. So all I can say is check as many times as you need to to make sure that you have got the right one.

Now comes the awkward part - you now need to strip off the insulation tape as much as you can so that you can grab hold of that wire carefully and pull it and see where it goes (all the wires are the same colour back there and they go from the plug into a small bundle, then through into some plastic channel into a larger cluster. You need to also strip off the insulating tape off the larger cluster. You should now be able to pull on the correct wire and find it in the large cluster - once you have identified it you can tap into it with a scotchlock or do it the proper way by cutting the wire, bareing the ends and joining you tap wire onto it (first putting a bit of heat shrink tubing round the cable so that you can pull it over the join once you have soldered it and shrink it to make a good join).

So now I have found it I have run a piece of wire and just insulated the end and coiled it (after checking that it indeed only came live once the engine was running). Will be running this through the firewall and connect it to the HHO relay and get this thing fired up (hopefully not literally "fired").

So anyway Connector 12 or CNA pin 10 is your one behind the cluster. A good point to take off for spilt charge systems as well. In fact I may well run the wire to a relay and then a connector block so that I can reuse it without overly pushing the current on the ignition light circuit. Will then connect the output from that relay to the HHO relay and then will still be able to use it for something else - say maybe I want to fit a split charge and leisure battery later.
 

uHu

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Once you have the toolbox at hand, it will take less than a minute to remove the air box and one intercooler hose. Seems to be a faster route.
But, of course, less colours, numbers, pins and counting.
 
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