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Headlamp bulb Dommie 99

Submitted by peter_brown1 on Fri, 07/10/2022
Forums
Electrical

My headlamp stopped working on low beam so assumed blown bulb. I ordered a 55/60w halogen one as replacement. Turns out it was a dodgy switch bulb was ok. 12 volts system 

Put the halogen one in very bright on main beam but quite dim on low, have cleaned all the connectors earths etc but still the same, fine with the original (35w I believe). Two questions really, will the wiring withstand the extra wattage ( self made harness from AO’s kits, modern reg/rect) and any ideas why the halogen is dim in low beam. Quite happy to stick with old bulb but also keen to use the new one.

Thanks

Pete

Submitted by ian_soady on Fri, 07/10/2022

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... you have the connections right? You may have swapped the earth / dip connectors in which case you'd have both filaments powered in one state and a poor earth in the other.

Checked with a multimeter, on the two sprung contacts on the bulb retainer, get 12v to earth on one pin, nowt on other, flick dipswitch and other pin live and first one now dead. No condition is sending 12v to both pins simultaneously. It works fine with the old bulb on dip and high, just the dip is is dim with halogen lamp. Thanks

Submitted by tony_gill on Fri, 07/10/2022

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i tried LED bulb on a dominator and commando both with pre focus units. Cheap from China a gamble. work fantastic. and will not overload wiring.  

Submitted by alan_osborn on Wed, 26/10/2022

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I would think your nice new connections to rear of your QH lamp are wrong. With H4 the centre is NOT the earth. Checking with a multi meter for 12V around such a lamp will lead you astray as you can read 12V both sides of the lamp (with a non working lamp) and the earth is lost. Electricity -funny stuff.

Submitted by peter_brown1 on Mon, 31/10/2022

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Hello Al, not quite with you on the H4 comment, the new halogen bulb is still BPF fitting

Submitted by tom_mcewen on Wed, 23/11/2022

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I changed to LED headlamp and tail-lamps from Paul Goff and can now be seen at all times with the headlight on, no load on the dynamo, (early Dommie) and no wiring worries. You need clean connectors and a good earth as the currents are so tiny. 

Classic Dynamo Regulators also are very helpful, so you can put the original regulator on the shelf and give your dynamo or alternator and the battery a better life.

Submitted by jonathan_newton on Wed, 23/11/2022

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Take your lamp cap with bulb inserted and test on a fused supply from your battery. If both  filaments light independently you have a wiring issue not a bulb issue.  

Current consumption on 12 Volt is roughly 3 Amps for original bulb and 5.4Amps for you High Beam Tungsten filament, 4.8 Amps for your low  beam.

Your cabling is, I guess is minimum 1mm Sq  which has a capacity of 16 Amps. Check your  battery AH and you have sufficient charging to maintain that load (plus rear lamp) on a long journey....

 

J

 


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