Full beam headlights but no dipped beam

[jondowning]

I won't have the opportunity to investigate this until the weekend, and so in the meantime I thought I would pick the collective JT brain.

Ive noticed that on rotating the dashboard switch, the sidelights work, but the dipped beam headlights don't. Upon depressing the floor dipper switch, however, both the full beam headlamps come on. I'm guessing that this is a fault with the dipper switch - if it was a fuse, none of the lights would work. If there was a loose connection at the dashboard switch, then, again, no lights would come on?

Any thoughts, please?

[robert lintott]

It looks like the dip switch or wiring to the dip beam. I recently bought a new dip switch from Holden www.holden.co.uk . for my Javelin , £40 including p and p. Some advertised are not quite the right fit in the floor. regards Bob Lintott

[Forumadmin]

Unless the wiring has been modified the dip switch is most likely although it could also be the wiring from the dipswitch to the lights (or more specifically the connector block where the wire splits to go to each side). Alternatively both your wires/connectors or bulbs could be blown.

[jondowning]

Thanks for the replies.

I inspected all the appropriate wiringn & connections: all good

I removed the dipper switch and wired up in the configurations suggested by the wiring diagram to mimic dipped beam/full beam usage, results as follows:

Blue wire(1) plus Blue & Red wire(2): both bulbs, both filaments lit
Blue wire(1) plus both Blue & White wires (4) both bulbs, dipped filament lit

I deduce then, that the switch is faulty, so over to Holden I go

But ... I hadn't noticed before that both filaments are lit when full beam is selected .. is this right?

[Forumadmin]

Are you sure the bulbs are wired correctly? This sort of fault can occur with earth not connected or a bulb incorrectly positioned.
What happens is the current passing through the main beam filament does not go to earth but travels through the dip filaments of both bulbs to the earth on the bulb that has an earth. Such a fault however should put all four filament on in dip mode as well. A meter across the dip switch with head and dip wires removed, but keeping the 12v feed on, should prove what is happening. Note that a bulb is better than a meter to test electrical problems as frequently you will get 12v but as soon as any current is drawn the high resistance feed drops the volts to zero or close to it. Similarly earths may show as continuous on the small current generated by a meter but not carry the higher amps required. A voltmeter between the battery chassis connection and on the earth of the component would in this case show a voltage above zero indicating a high resistance earth.

I actually have a switch on the panel to allow both head and dip to function as this is good when rallying across an undulating or winding road. This only works if you have an alternator though , a dynamo does not give enough amps.

[jondowning]

Fixed!

The Holden switch is a good copy of the Lucas original. The beams look to be behaving themselves now, which is good news, as i'm planning to use the car this week to travel to and from Telford, where I'm working this week (200 mile round trip)

[Forumadmin]

Probably made in China so be prepared to buy another! I bet it won't last 60 years!