Which wire in the engine bay is live only when Ignition is switched on?

[Ian]

I need to wire my electric fan thermostat to a live that is only live when the ignition is on, Which wire in the engine bay can I use for this?

 

[Ian]

I could also do with a switched live in the interior, wheres the best place to take this from?

Car electrics are not my strong point.

 

[Mr.F]

Engine bay - try live feed to screen wash pump. There aren't many more except around the coil which is not ideal for electric fan.
Interior - there are switched lives around the fuse box and also at the ignition switch itself.
Ideally buy a multi-meter and test for yourself...
If your conversion needs lots of switched and unswitched lives, then setting up a sub-station fuse box would be a good idea.

 

[Wyn]

Ideally buy a multi-meter and test for yourself...

tis what I did sept used one of them sharp pointed 12v test lamps to jab various wires till I got lucky

So far so good

 

[Ian]

Surely the feed to the screen wash pump is only live when you press the button for the screen wash? Looks like I may have to run the power from something inside.

I'll have to use a multi-meter I guess and find the live wire from the ignition, but not sure how to go about it after that, I need a switched live for my new guage and I had thought I could just splice a wire into the igniton live but I guess you can't really do this for the fan aswell as there would be too much draw?

 

[Mr.F]

Screen wash pump is supplied with a live and earthed via the switch. Just used it to power a Kenlowe fan board - it works!

 

[Ian]

Thanks for the info, sounds like that could work well, I'll have a look tomorrow.

 

[SKiddell]

Just to understand what you are trying to do (electrics are my strong point)

Where do you intend to run the main power to the fan from as the current draw to a fan is significantly greater than a washer pump (3 – 4 times) and as such the wiring infrastructure needs to be more significant.

 

[Rob Gaskin]

When I fitted my Kenlowe fan and electric Facet fuel pump I wired them from the fusebox. I can't remember the exact circuits but I know the fan was into an ancillary cct so that I could let it run after a track session without the ign on. I fitted appropriate 'inline' fuses in both.

240Z not 260Z.

 

[GTR-240Z]

Ian, I would run your electric fan via a relay. Find a 12v ign source to power up the relay and then run a new fused wire from the battery which powers the fan via the relay. If your doing an RB swap in the future, I would consider making a sub loom with relays and new wire to power your ecu, and fuel pump as well. Running any of that stuff through the old datsun wiring and ignition switch should be avoided.

 

[Mr.F]

Modern Kenlowes come with a controller that incorporates relays and switching alternatives. Obviously the fan motors require a heavy duty live feed, via the relays. All we are talking about here is a low current feed to the control board and coil side of the relay. A similar wire is usually provided to run an override switch inside the cabin.
Never consider running electric fans which are directly switched without relays!

 

[Ian]

Just to understand what you are trying to do (electrics are my strong point)



Where do you intend to run the main power to the fan from as the current draw to a fan is significantly greater than a washer pump (3 – 4 times) and as such the wiring infrastructure needs to be more significant.

Its fine, the washer pump live will just be for the control circuit, there will be a fused wire straight from the battery to the fan to power it. I also need a switched live inside the car for a manual override switch for the fan, again just a control wire. Will need a ignition switched live for my new fuel guage, I'm sure this won't be a big draw but idealy I'd have it from the fusebox, I just need to workout whats live when the ignition is on, the wiring diagram I have are rubbish and not much help.

Ian, I would run your electric fan via a relay. Find a 12v ign source to power up the relay and then run a new fused wire from the battery which powers the fan via the relay. If your doing an RB swap in the future, I would consider making a sub loom with relays and new wire to power your ecu, and fuel pump as well. Running any of that stuff through the old datsun wiring and ignition switch should be avoided.

Thanks for the advice, this is what I will be doing, I'm running a Kenlowe Electonic Thermostat.





I will definitly make a sub loom for when I swap the engine, will probably make a whole new fuse/realy box inside and small fuse/distribution box in the engine bay.

 

[Rob Gaskin]

I can't remember the exact circuits but I know the fan was into an ancillary cct so that I could let it run after a track session without the ign on.

Yes as Mr F states - this is not the main motor feed just the control feed.

 

[240L31]

Super old thread, but I got a similar question: where can a find a switched power inside the cabin which is only on when the engine is running?

 

[toopy]

I used a redundant blue wire i found near the washer bottle that is ignition start/on live only, that i used to power the relay for my fuel pump. No idea where it is inside the cabin though.