Mate has hid kit twin bulb for hi low beam,, but u can only get hi or low to work not both... Why is this?? Tryed it on mine and his Scooby no joy,,,tryed on fiesta think he said it was and plug it in and u can switch between both hi and low beam,, why can u not on Scooby??

 

You just need to add a relay to the high beam output so that the low beam stays switched on when high beam is engaged. I.e. switch on high beam/relay energises and supplies voltage to low beam lighting circuit. Any auto electrician could do this quite cheaply.

 

The system will be designed to do this as the wiring will be designed to draw enough current to supply one set of lights. If you draw double the current across the same circuit you will induce more heat and risk melting the wiring.

Nearly every car I have owned or worked on switched between dipped and main beam and do not run with both on.

 

If you run the power to the dipped lights directly from the battery and through the relay you wont have above problem. The high beam voltage being used to trigger the relay.

That is if it is absolutely essential that the lights operate together. I know on my 2006 STi they both come on together, but the dip are HIDs whereas the full beam is not.

 

I am happy with how the relay works; using the feed directly from the battery just becomes untidy. You still need to understand where the power cuts in the original circuit unless you are propsing fitting the relay to run a higher power feed that will power both lights simultaneously using the main beam feed to switch that in which case you would have 2 independant feeds running to the dipped lights - one to operate the lights normal from the cars standard loom and the second feeding both the main and dipped from the relay

I'm frantically trying to scribble a wiring diagram for this whilst sat here on night shift. I'm envisaging it being no different to having the dipped with one wiring connection for normal use and a seperate feed, almost like extra front fogs, that energises the bulb when you flick the switch

In terms of the factory STI lights, the bugs are the same - non-HID lights switch independantly but on HID versions both stay on together and that is with the same wiring loom on both (albeit with a ballast included).

 

JonMc, yes sorry, i was quoting you but replying to original OP (in my mind at least)

Possibly this:

 

The way that an H4 HID "Bulb" works is to alter the position of the discharge, the bit producing the actual light, so as to APPROXIMATE the positions of the two filaments in a halogen H4 bulb.

The actual light output remains the same, so trying to get "both to work at once" won't work, since all you will be trying to do is stick the "bulb" half way between two positions.

 

The way I read the OPs comment is he has a twin-bulb kit, ie 2 separate bulbs rather than a dual bulb with both filaments. This mean 2 independent circuits

 

Thats the way i read it too

 

Sorry, I may be wrong, but he said "twin bulb (singular) for hi-low beam".

I read it as one bulb doing both, ie: H4.

Perhaps the OP could enlighten us?

 

All down to interpretation and understanding and I'm sure we've been here before discussing side, low, main and high beams

If it is a single bulb with twin/dual filaments I agree that it cannot be done; both on together is only properly achievable if there are 2 separate bulbs