IVA Rear Fog Light Rules

[Steve_D]

IVA rules require that a rear fog light must only operate when the headlights are on dip or main beam.

A recent IVA rule change now requires that when the headlights are turned off the fog lights shall not come on again unless re-selected. (You can fit a warning buzzer but I’m not interested in that option).

I have a circuit that will work and only requires the use of a bog standard relay and a momentary switch/button for fog lights.

Its only drawback is that if you decide you no longer require fog lights the only way to switch them off is to switch the headlights off and on again. Not a major issue I feel but does anyone have a better circuit?

Steve

[Steve_D]

Thanks Dave.
Was just about to dive back under the dash of a car to fix this.

Would still like the electric wizards to ponder the problem as I doubt this will go away for too long as the 'fog light left on' problem seems to be on the increase.

Steve

[Steve_D]

GarethGTR said:

I am mid IVA now, and am told that it must be there.

i.e. Fog Lights must ONLY come on when selected. If lights are turned off and then the fog light state must be reset.

Gareth

Sounds like now is the time to challenge it with your test station.
If they stick by the ruling in the book then I have a circuit you can use.

Steve

[Steve_D]

PaulKemp said:

I would think a momentary switch and locking relay would do the job

A latching relay only unlatches with the next push of the button. You need something that unlatches when the headlights are turned off.

CBS have a unit but £30 is a little steep.

I have a circuit for one standard relay but if you want the fogs off during a journey you need to turn the headlights off and on again.
I have another circuit using 3 relays but have not tried it yet but you can turn it on and off from the button.

Steve

[Steve_D]

Fastpedeller said:

I seem to recall that some cars with a rotary switch use a mechanical switch to turn on the fog lights (push the whole button), so that when the heads are turned off the fog is also turned off.

Yes many cars have this mechanical self cancelling feature in the stalk but lots of kitcars do not use stalk controls hence the original request for an electrical solution.

Steve

[Steve_D]

Snake the Sniper said:

Would it not be easier to just feed a fog light switch from the out side of the dipped beam switch and then on to a normal relay? I might just be being thick, but I'm not sure I see the problem here.....

In your example the fog light would come on again when you next switched the headlights on which (according to the current issue IVA manual) is not allowed. The fog light must revert too, and stay in, the off condition when the headlights are turned off.

Steve