The headlamps on my Land-Rover are like candles in jars despite reasonably new reflectors, good ( Osram ) H4s and new, clean earth connections. I was going to check the voltage at the bulbs but realised that I have forgotten the correct reading! Can anyone help and should the bulbs be conected to the three way plug at the time of the test or not?
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I would check the voltage drop, rather than the absolute voltage. The tests are quick, simple, and require no dismantling.
With the lights connected and switched on;
Put the positive of your voltmeter on the positive terminal of the battery and the negative lead onto the live terminal at the bulb. Read the Voltage.
With the lights still connected, and still on, put the positive of your voltmeter onto the earth terminal at the bulb, and the negative multimeter lead to the negative terminal of the battery. Read the voltage.
If either of these tests reads more than, say, half a volt, you have a bad connection, which is preventing your bulbs glowing properly.
If these tests show that your connections are good, read the battery voltage with the engine running, to make sure your charging system is OK. Should be reading in the 13.5 - 14.5 volt range.
Number_Cruncher
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Thanks. I'll get out and check things while there is still enough daylight to see what I'm doing.
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You could always run the headlights direct from the battery via a relay which is turned on by your headlight switch if your wiring is getting past it a bit.
Makes a big difference when i used to wire cibies up
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I've just done a check and found a drop of 1.5V between the battery and feed to the bulb but the earth is ok. The loom is only two years old so I suspect a conncetion or switch. It might be better to the advice and use a direct feed and relay.
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>>It might be better to the advice and use a direct feed and relay.
Yes, that's reasonable - at least you know the earth side is OK. I would very strongly suggest that you make sure the live feed directly from the battery is fused close to the battery, and the live wires are carefully routed away from sharp metal edges.
Number_Cruncher
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Before rewiring as a workaround, I'd try and find the cause of the voltage drop (work backwards from the headlight towards the fuse panel following the loom).
If the problem is in a multiplug connector it's highly likely that it will cause problems in other circuits later on which may not be as easy to diagnose.
First and easiest thing to check tho' is the existing relay. Contacts do get burnt over time especially if there was any misalignment during manufacture.
Kevin...
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PS.
You haven't installed higher wattage bulbs have you?
Kevin...
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The bulbs are standard 55/60w and there is no relay in the standard loom.
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Mmmm,
What model/year is it?
Has it always been like this or is it something you've just noticed recently?
A 1.5V drop isn't excessive, (less than 0.5ohms), so I don't think there's anything wrong with your wiring.
Try temporarily wiring the lights directly to the battery with a heavy gauge cable. I doubt that you'll see any difference.
You might be better off adding some driving lights relayed off high beam.
Kevin...
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as above? a recent problem or been like it for ages etc?
Could it just be bad setting of the headlamp aim?
Is it just dip beam or main and dip?
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Bob
The most common problem with L-Rover headlamps is the bulb plugs themselves. It's necessary to measure the voltage on the actual bulb pins themselves to get a true picture; the back of the connectors is before the problem.
As said; 1.5 volts drop in an unrelayed circuit isn't good, but it's not unusual. Best practice is to fit a double relay, fed directly from the alternator's output bolt, down thick cable, with soldered terminals.
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I've done the relay setup on a VW and it improved the light output tremendously. The light was much brighter and whiter, highly recommened. I think you'll find the earth side high resistance too. Mine was losing 2.5V at the bulb with the engine running, I took a reflected light reading of white pained garage doors with my SLR camera before / after and the reading showed a 100% improvement
Relays and fuses were from a scrapyard, wire and a box to house it all were from maplin. I fixed the box to the side of the battery with a cut down bicycle inner tube and a bit of velcro
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Thanks all. The entire loom is only just over two years old and there are no "nasty" connectors anywhere - the vehicle is standard spec. I'll go for the relat approach this weekend and see if there is any improvement.
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