If you are installing headlight relays on a 1987 through to 1991 T25's built for the UK market it might have Dim Dip circuit fitted. If so, the Dim Dip resistor must be disconnected
why must it be disconnected? and what will happen if you dont?
cheeers
Josh
sorry to bump this but I am very curious to know if and why I need to disconnect my dim dip circuit when fitting headlight relays. I can see no reason why I would need to, but wonder why It says in the Wiki that you MUST disconect it. cheers
Dimdip= dipped beam at slightly reduiced voltage (reduice the voiltage a bit power goes down alot, its a more extreame version of what your fitting relays for - think dimdip is about 8-9V).
The dimdip circuit joins the diped beam circuit in the fusebox just before the loom splits into left and right fuses and wireing. This is the circuit you use to trigger the new dipped beam relay, but depending on where you take your relay trigger depends on how it behaves with dimdip.
If you fit relays after the fusebox (most seem to do it this way), besides looseing the use of the headlamp fuses, dimdip feeds into the relays with enough current to trigger them, thus conecting the headlamps to the full power surply meaning what was once dimdip becomes full power diped beam - you won't be able to have dim sidelightish level lighting when the engine is on. Disableing dimdip means you just get sidelamps on the first position like when the engine is off, non british spec or more modern vehicles are like this anyway so it doesn't matter.
If, like me, you fit the relays between the dipswitch and the fusebox everything still works as OEM, you still get the headlamp fuses on the fusebord, full headlamps are still brighter as you've bypassed all the switches and their slight voltage drops, and dimdip still works as it comes in after the relays.
Govkid- if you lights are bright on sidelight then it it means the dim dip ( if fitted) is triggering your relays for full brightness. I fitted my relays so the dim dip still works as normal when the sidelights and engine are on. so I guess I am ok.. I understand now that the warning to disable dim dip is if you have wired the relays after the fusebox not before the fusebox.. is there any point in fitting the relays after the fusebox? does it sap volts and thats why people do the relays after the fusebox?
Thing is, I'm running a headlight booster which doesn't give you an option to do anything but boost both main and dipped (unless I somehow bypassed it). That said I'm not sure I understand whats going on here. Are we saying theres a voltage dropper for dipped? I'm not aware of anything like that on mine and wouldn't bulb manufacturers take that into account as standard then otherwise you'd be wasting energy though a fat resistor.
In the normal run of things, dipped should still light up the road enough at night to pick out the odd stray cat or child, in fact you're more likely to face those kind of dangers on dipped than you are on the open road on full. If I am too bright on dipped, I'm not actually dazzling anyone at mo (run numerous checks for that even after they were set up by garage). In fact, as I mentioned in another thread, I lowered them a little to what seemed more reasonable for both pedestrians and other road users. Even on beetles I wasn't aware of any gadgetry fitted to reduce voltage to headlight bulbs on dipped - they just dip by switching to other filament in bulb itself.
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covkid- dont confuse normal dipped with dim dipped. Normal dipped is supposed to be bright. dim dipped is different, it only works with side lights setting ( 1st position on the light switch) and only when the engine is on! the dim dipped option supplies a reduced voltage via a large resistor to the main dipped headlight circuit when the engine is on and the sidelights are on.
