Ken,

That's all done and dandy until you to what I do

Distracted and not paying attention - bridged the wrong thing and burnt the loom out. I now have a pre dimdip loom!

So no jumpers. Looks tidier

Are you sure it's got dim dip Chris? I'm almost certain the loom came from an '82/'83 Y reg car.........

Could it be be both bulbs blown?!

I had exactly the same fault on my 2cv (which has perfectly good and trouble-free dim-dip as I never use that setting) a few weeks ago. The cause was extremely simple: the headlamp dipped beam bullet connector in the bundle of wires strapped to the headlamp bar had come apart.

The repair cost all of zilch and took about fifty seconds and involved just removing the straps and checking the connectors. Look for the simple causes first...

Rob,
sorry to disagree, but avoiding the switch position which activates the dipped beam at reduced intensity will not protect your light switch, since the whole problem with dim-dip is that the dipped beams when at full intensity, plus the fog light when it's switched on, are all fed via the side light contact.

If you check the wiring diagram below, you should notice that all the only function which the dipped beam contacts do is activate relay 1, a total load of about 6 watts.

In order to feed the dipped beams from the 'normal' light switch contacts, a jumper lead must be installed between contacts 1 and 5 on relay 1, after which the side light contact will no longer have to carry a load of 125 watts with conventional bulbs, even more with halogens fitted...



Dimly dipped by slcchassis, on Flickr

ken

So,

What pointo on the light switch, is the "dim dip" setting?

'Sidelights' setting on the light switch and with ignition 'on'.
That energises the mauve lead, shown at the left in the wiring diagram.

Middle lead is energised with both of the 'dipped beam' positions but with the original setup, it serves only to activate the relay which bypasses the resistor.
Lead at the right is energised with 'main beam' position.

The whole lashup really was bonkers...

ken.

Fair enough Ken, but on my car it works, the light switch doesn't even get slightly warm and I've always been running halogens. The loom is entirely as originally mangled by Mangualde.

My real point though was that people seem to be jumping straight to complex causes for the fault described when it could just be the exact same cause of the exact same fault which I recently had.

As there has never been even the merest hint of an issue with the dim dip on my car even when I'm using the rear hi-vis light I'll leave it as is.

Rob,
as you say, fair enough...
But if your theory is correct, shouldn't the original poster be checking _both_ bullet connectors at the light bar, since he reported that there was no dipped beam on either headlamp?

ken.

But it's not a theory, Ken. On mine the fault was a single common bullet connector at the n/s end of the lighting bar. Whilst disconnected both headlamps had no dipped beam but main beam and sidelights were fine and when reconnected everything worked correctly once more.