Rear fog goes out with High beam?

[Maverik]

86 reg LR90, original loom etc.

When I put my side lights then main lights on The fog light will illuminate - what I want, when I flash my headlights its fine, but when I puch the stalk forward to keep my high beam on, my rear fog goes out, is this right? More importantly is it an MOT failure?

Another question regarding hedlights, when you put high beam on is main beam meant to stay on? or is that meant to switch off?

cheers

Mav

[chadler]

It's meant to do that, in fog if you have full beam on then you'll just light up the water droplets, hence there is no circumstance where if you need one that you need the other.

[reb78]

As above. This is normal on many modern cars.

[Maverik]

I hadn't noticed it before, and all though it makes sense, I just wanted to check.

Cheers

[Retroanaconda]

With regard to the headlamps, if you are on normal beam and flash onto high beam, the normal (dipped) beam will stay on. If you push the stalk forward into high beam mode, the dipped beam should turn off.

That's how all mine are anyhow.

[western]

With regard to the headlamps, if you are on normal beam and flash onto high beam, the normal (dipped) beam will stay on. If you push the stalk forward into high beam mode, the dipped beam should turn off.

That's how all mine are anyhow.

correct

[Maverik]

correct

Is there any perticular reason for this? Mine doesn't do this anymore but I'm not entirely sure why not, I've put in new wireing for the headlamps with relays, and just used the feeds from the switches as the relay signal.

I've not actually seen the lights change from the front only heard my relays clicking. As far as I can work out it doesn't really matter they both stay on.

[western]

Is there any perticular reason for this? Mine doesn't do this anymore but I'm not entirely sure why not, I've put in new wireing for the headlamps with relays, and just used the feeds from the switches as the relay signal.

I've not actually seen the lights change from the front only heard my relays clicking. As far as I can work out it doesn't really matter they both stay on.

if visibility is clear enougfh to use main beam, then rear fog light [RFL] is no longer required & it prevents you leaving the RFL on to distract/blind/dazzle other following drivers if you forget to turn it off.

RFL should only be used when visibility is 100meters or less.

[Aragorn]

Surely as soon as you disengage main beam and drop back to the normal dips due to oncoming traffic etc the rear fog would then come back on?

H4 bulbs arent designed to have both filaments burning at the same time, which is why when you latch main beam (as opposed to just flashing it) it cuts out the dip filament. Cars fitted with separate Dip and Main lamp units will normally keep the dipped bulb on when you both flash and latch main.

[western]

but once the rear fog control relay has had it's power cut off, it cannot put the light back on, reckon there must be a interlink inside the relay.

just checked my '89 110, with rear fog on & main beam selected, rear fog stays on, so maybe not all vehicles have the interlink or mine doesn't work.

[reb78]

Mines the same Ralph - same age as yours as well. I have driven other makes that have this where the rear fog goes out with main beam on, so presumably land rover brought it in on their vehicles some time in the 90s. Although, just re-read OPs landy is an '86....puzzling.

[Retroanaconda]

Isn't the fog light just a switch?

I know Td5-era vehicles have a one-touch fog light ECU, but ones prior to that just use a straight switch which is fed with a 'lights on' feed, don't they?

[western]

There's a relay in circuit too if the vehicle originally had dim dip headlight system fitted, LR call it a rear fog inhibit relay, has a plain blue wire from dip switch to inhibit relay to main light switch.

should be locatyed either behind instrument pack or behind the fusebox.

[Aragorn]

Fair play to landrover if thats the case, as most cars of that era simply have a normal switch which invariably means that after some fog you see cars driving around for weeks afterwards with their fog still on.

You sure the inhibit relay doesnt just ensure the fog is only on when the lights are on?

Edit: RAVE suggests even 300tdi's had a non-latching switch for the rear fogs, but doesnt cover earlier motors.

[western]

here's the connection diagram from my defender workshop manual wiring section.