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What does this relay do?


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Does anyone know what the purpose of this relay is:

med_gallery_22916_1107_146405.jpg

The rear view shows that is switches two blue wires (one with a pink sleeve, one with a black sleeve) and the coil wires are white and black:

med_gallery_22916_1107_62048.jpg

I think it is something to do with the lights, but I can't find it on the wiring diagram anywhere.

The vehicle is a 1990 Defender. It has dim dip but (according to the manual at least) this does not rely on a relay.

Any ideas?

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Does anyone know what the purpose of this relay is:

med_gallery_22916_1107_146405.jpg

The rear view shows that is switches two blue wires (one with a pink sleeve, one with a black sleeve) and the coil wires are white and black:

med_gallery_22916_1107_62048.jpg

I think it is something to do with the lights, but I can't find it on the wiring diagram anywhere.

The vehicle is a 1990 Defender. It has dim dip but (according to the manual at least) this does not rely on a relay.

Any ideas?

Im sure Ralph will be along soon

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So what is the 'headlight relay' for then? There is no component with this name on the wiring diagram!

The switched wire colours are plain blue, but one has a pink sleeve and one has a black sleeve (shown in the picture). The wires are not the dip circuit colours.

Still confused!

Nick.

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So what is the 'headlight relay' for then? There is no component with this name on the wiring diagram!

The switched wire colours are plain blue, but one has a pink sleeve and one has a black sleeve (shown in the picture). The wires are not the dip circuit colours.

Still confused!

Nick.

I couldn't find it on the wiring diagram either, but in the list of relay locations it says the 5 in fuse box are

brake check

start

rear fog inhibit

headlamp

fuel pump isolation [fitted to aviod incorrect fitment of the other 4 relays]

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So what is the 'headlight relay' for then? There is no component with this name on the wiring diagram!

The switched wire colours are plain blue, but one has a pink sleeve and one has a black sleeve (shown in the picture). The wires are not the dip circuit colours.

Still confused!

Nick.

trace the blue wires to see where the connect too.

LR sometimes use a coloured sleeve instead of fitting a dual colour wire, part of my glowplug wiring is yellow with a black sleeve about 10 to 20mm long.

further wiring diagram searching reveals a relay that has 2 Blue wires & a Black wire & a White wire, it's listed in the diagram key as REAR LIGHT RELAY

one blue connects to main light switch

other blue connects to the dim dip transformer

Black wire goes to Earth

White is a ignition controlled 12V feed

so it is associated with headlights & is part of the Dim Dip wiring.

extract of wiring diagram, refer to relay identified as 9.

post-20-081727600 1288285232_thumb.jpg

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I couldn't find it on the wiring diagram either, but in the list of relay locations it says the 5 in fuse box are

brake check

start

rear fog inhibit

headlamp

fuel pump isolation [fitted to aviod incorrect fitment of the other 4 relays]

I think that's for 300Tdis isn't it?

My 200Tdi certainly doesn't have a starter relay, just a white/red from the ignition switch to the starter solenoid.

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I think that's for 300Tdis isn't it?

My 200Tdi certainly doesn't have a starter relay, just a white/red from the ignition switch to the starter solenoid.

not 300tdi wiring diagram, simply because I don't have any in paper form, that came from my Defender workshop manual which includes 200tdi upto 1991, I think you'll find the start relay behind the fusebox if your 110 has the older glass fises like mine which also has a start relay.

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Western is certainly correct - this is the headlight relay. I'm not sure what it is supposed to do, but having got the battery connected again today I have proven that the headlights don't work without it.

Am I right in recalling that the headlights are supposed to go out when you crank the engine? If so, that's probably what this relay does (but my vehicle no long seems to have this function so it looks like I have got something wired up wrong).

Where does that wiring diagram come from, Western? I'd like to get a copy of it if I can.

Nick.

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Western is certainly correct - this is the headlight relay. I'm not sure what it is supposed to do, but having got the battery connected again today I have proven that the headlights don't work without it.

Am I right in recalling that the headlights are supposed to go out when you crank the engine? If so, that's probably what this relay does (but my vehicle no long seems to have this function so it looks like I have got something wired up wrong).

Where does that wiring diagram come from, Western? I'd like to get a copy of it if I can.

Nick.

from my genuine paper Defender wokshop manual upto & including 200tdi/1991 vehicle, PM your e.mail & I'll scan the diagram & ident list for you.

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I stand corrected, my 200Tdi workshop manual lists a start relay too!

Mine has blade fuses, but I could have sworn there wasn't a starter relay when I was playing with the starter circuits...but there must be somewhere it seems. If the workshop manual is to be believed :huh:

The 2006 Td5 bulkhead I have sat in the workshop certainly has one.

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I stand corrected, my 200Tdi workshop manual lists a start relay too!

Mine has blade fuses, but I could have sworn there wasn't a starter relay when I was playing with the starter circuits...but there must be somewhere it seems. If the workshop manual is to be believed :huh:

The 2006 Td5 bulkhead I have sat in the workshop certainly has one.

should be in the same location as Nick's first photo, the relay labelled CRANK

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Many thanks for the diagram, Western. I may now (finally!) have the right one for my vehicle!

Am I right in recalling that the headlights are supposed to go out when you crank the engine?

Can anyone confirm if this is correct, or did I imagine it?

Nick.

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  • 8 months later...

They'll probably dim when it's cranked, due to the current draw of the starter. But I'm not aware of any automatic switch off.

I was always taught to not turn them on until the engine was running, though I see plenty of people turn them on first, or just leave them on all the time :(

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I can certainly say (especially after much help from Ralph as usual) that on my 97 defender the headlight relay is literally just that. It has nothing to do with whether the engines cranking, it just uses an ignition feed to activate the relay...ie without the ignition on, you cant switch on the headlights, only sidelights. Seems a bit overkill perhaps to have a relay for this but I guess they see dipped and main beam as powerful enough to require relay switching rather than path the power through the main switch. Of course if you have a dimdip relay then that too is part of the circuit, but the headlamp relay doesn't do anything clever. Like I said, it jsut prevents the headlights from being switched on without unless the key is turned.

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