Thread: Lucas ... the lord of darkness (2a light problems)

All,
time to fix the lights on my ex-army 2a.

For some time now the lights in the 2a don't work. High beam is fine, but the normal (low beam?) lights don't do much. Have to say that I have only a bulb in one side, so never thought of it much.

Thinking it was a bulb problem, I pulled the bulb out. For some reason I decided to test it ... connected it to a battery and both lights work, so it seems that bulb is fine.

Alright then ... must be a cabling problem ... voltmeter comes out ... measures 12.something Volt on the high beam connection. Hitting the foot switch to switch off high beam ... hmmm ... the other connector measures 12.something Volt as well.

So I grab the bulb, connect the negative and hold the contacts on the bulb individually to the contacts on the harness .. lights in bulb come only on when connected to the high-beam contact in the harness.

Any thoughts ? Voltage measures fine, earth must be ok as it works fine for high beam.

Thanks,
Dante

The problem is almost certainly a bad contact, perhaps as suggested the higher current from the high beam is making temporary better connection.

The headlights are earthed to a bolt on the radiator panel, on mine it is to the right of the place for the bonnet catch (not normally fitted on the army 2a). Locate this, and disconnect this earth from there and run a temporary earth lead to the battery negative. it is likely that this will fix the problem, but even if it does not, it will eliminate earthing as a problem. The earth back to the battery depends on the following bolted connections, any of which can be faulty:-

1. Connector to radiator support panel.
2. Radiator support panel to mudguards (could go via the bolts to chassis, but these have insertion rubber in the joint!)
3. Mudguards to bulkhead or steering box support.
4. Bulkhead or or steering box support to chassis
5. Chassis to engine (assuming the battery is earthed to the engine).

If this temporary earth fixes the problem, decide what to do about it - what I did was put another tag under the same bolt as the earth connector for the lights, and ran a wire directly to the battery negative terminal.

If it does not fix the problem, work back from the lights with a voltmeter, checking the voltage all the way, with the headlights on - the voltage drop may not appear with no current drawn. You can check the voltage at the connectors, these vary a little according to model, but there should be one (for each beam) on the RH side of the radiator panel, on each of the three leads where the dip switch harness joins the main harness, and on the light switch.

It is sometimes useful to check voltage without opening a connector by using a pin to go through the insulation, as this allows you to check voltage while the lights are drawing current. Also consider the possibility of the switches, either the main light switch or the dip switch being faulty, and again, check the voltage while the lights are on.

John

PS If you don't have a wiring diagram, (e.g. workshop manual or owners manual) get one. The military has some addition wiring, including a blackout switch which involves the lights. This is likely to have been removed, and you should suspect the connections replacing it.