Circuit for Daytime Running Lights

[sorcerer]

I believe that it's preferable for DRLs to be on only when the engine is running and not in either the ACC or IGN key positions of the key switch. I really don't want to be running a wire from the front to the back of the car to pick up on the fuel pump connections there, so can anyone tell me which fuse supplies the pump and the location of it - or indeed, any other circuit that is only energised on 'engine run' that I could tap into, in the engine bay please?

[rayofsunshinegbr]

Hi Sorcerer

I have just seen your post, but unfortunately cannot give you any information. However I am very interested in whether you have "sourced" (please excuse the pun!) DRL's that will fit the 400h.

Please would you let me have the information and in return I will investigate the wiring.

Many thanks in anticipation

Ray

 

[sorcerer]

Certainly Ray - these are the beasties

With a bit of furtling and a couple of relays they can also be made to go off when you switch on your sidelights, just as 'real' factory-fitted DRLs do. If you're not sure how to do that I'll post more tomorrow but for now, I've got to go and pick up wifey from her weekly darts night

[sorcerer]

After some investigations with my multimeter, I discovered that there are no fuses in the engine bay fusebox that are only live when the engine is running. In fact, there is only one fuse that becomes live when the ignition is switched on, all the rest are either permanently live or only become live when lights are switched on.

So, that 10A fuse at the front it is then - or not

Turns out that the construction of the fusebox means that the piggyback fuse tap can't be pushed fully into place and it's not even viable to cut out a notch either, so it looks like I'll have to pick up power from the fusebox in the driver's footwell after all. No great hassle, just means that it'll be a few days before I can carry on with the job.

 

[bobmc]

Won't it go in fully if you rotate it 180 degrees?

 

[sorcerer]

3 minutes ago, bobmc said:

Won't it go in fully if you rotate it 180 degrees?

 

Yes, it'd fit but the circuit wouldn't be protected by the fuse. The live bus bar is on the left of the fuse, so current has to travel up the left leg of the fuse tap, through the fuse and out to the load through the red wire. Turning it through 180^o  will mean the current doesn't flow through the fuse.

[bobmc]

Fair point, the 'live' pin is usually the one furthest from the red wire ?

 

[sorcerer]

31 minutes ago, bobmc said:

Fair point, the 'live' pin is usually the one furthest from the red wire ?

 

On the fuse taps, yes. You need to test the car fusebox to see which side of the fuse holder is live, then make sure to insert the fuse tap the right way round. This isn't my image but it shows how they work:
 

[bobmc]

I still think it would work if you reverse it, you would just be fused twice

Top is how it would be wired normally, bottom is how it would be fused if you rotated it, fuse 3 would be carrying combined load though

 

 

 

[sorcerer]

As my dear departed Granny used to say, "Well, I'll go t'foot of our stairs." I do believe you're right Bob

I think the fuse should be alright with the combined load but I'll make sure to get a spare just in case. It's the EFI2 (Or was it EFI1 - can't remember now) and I'll be using my tap off to energise the coil of a relay, which I'm sure won't take much current draw over and above what it was handling anyway.

Thanks for that sir, excellent

[bobmc]

You're welcome John

Do you know what's on the 10A circuit?

If you're running a relay (100mA?) and a couple of LED's (700mA each?) you shouldn't be drawing more than 2 or 3 amps extra

[sorcerer]

3 hours ago, bobmc said:

Do you know what's on the 10A circuit?

Off the top of my head, no, and I'm away for the weekend now but will look when I get home and let you know.

 

3 hours ago, bobmc said:

If you're running a relay (100mA?) and a couple of LED's (700mA each?) you shouldn't be drawing more than 2 or 3 amps extra

This particular tap is for the relay coil alone - power for the LEDs will come from elsewhere via another fuse.

The idea is that Battery voltage (suitably fused) goes to the input of Relay 1. The coil of that relay is energised by that 10A EFI fuse when the ignition is on, switching Battery voltage to the NO contact and on to the input pin of Relay 2, through its NC contact and out to the LED DRLs.

Relay 2 has its coil energised by a feed from the sidelights, so that when the sidelights are switched on the relay pulls to the NO contact, thereby cutting the supply to the DRLs for night driving.