Headlight not working

[WonkoTheSane]

Started up to go for a ride for the first time since new battery and new R/R and the headlight is dead but the high beam light on the instrument panel is lit at all times (whether the switch is on low or high beam).

All other lights are working (rear, brake, indicators). Have I buggered something fitting the R/R, or is it likely to just be a dead bulb (is there a single bulb or one for high/low?).

I have an irrational fear of electrics so would appreciate advice as I don't trust myself not to misunderstand the manual and blow something up.

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[Miles Long]

Started up to go for a ride for the first time since new battery and new R/R and the headlight is dead but the high beam light on the instrument panel is lit at all times (whether the switch is on low or high beam).

All other lights are working (rear, brake, indicators). Have I buggered something fitting the R/R, or is it likely to just be a dead bulb (is there a single bulb or one for high/low?).

I have an irrational fear of electrics so would appreciate advice as I don't trust myself not to misunderstand the manual and blow something up.

WonkoTheSane-
I remember from your original post regarding your bad RR, that you were experiencing an overcharging condition (17 volts+). This may be the cause of you headlight bulb burning out.
I think if one or both filaments fail, the dash bulb will stay lit. This is a safety feature, to let you know that there is a problem. Same goes if the ground wire is disconnected (I know this because I once installed a headlight override switch by splicing into the ground)
I'd first try just inspecting/replacing the headlight bulb. And yes, just one bulb is used for high and low(or "dip", as they say in the U.K.)
Cheers! MilesTheSlightlyPsychotic

 

[WonkoTheSane]

Thanks, Miles. I do modify my vocabulary for a transatlantic audience when I remember You're right about the overcharging and I was hoping it might be something like that. Confirmation bias at work. Is a blown bulb obvious?

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[sdt354]

Thanks, Miles. I do modify my vocabulary for a transatlantic audience when I remember You're right about the overcharging and I was hoping it might be something like that. Confirmation bias at work. Is a blown bulb obvious?

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Sometimes they turn black. An ohm meter will show open circuit on a burnt element usually. A little resistence on good elements.

 

[Fire-medic]

I had what I thought was a bad switch but was only a burned out or bad beam filament which was actually making intermittent contact & light. Brand-new out of the box too which made me think a bad switch. Now my switch is v. clean though. Sometimes the simplest solution is the correct one.

Also until your filament pops from excessive voltage, your headlight will be very bright! The bulb filament is actually a type of fuse if you will. Audio speaker manufacturers have used bulbs as a protection circuit for years.

 

[Miles Long]

I had what I thought was a bad switch but was only a burned out or bad beam filament which was actually making intermittent contact & light. Brand-new out of the box too which made me think a bad switch. Now my switch is v. clean though. Sometimes the simplest solution is the correct one.

Hey FM - A tad off topic, but google OCCAM'S RAZOR.
Along the same lines, there is also an old French expression, that loosely translated goes...
"Perfection in design is achieved not when things are added, but when everything not required has been taken away"

Of course north americans, in all their eloquent glory, have long ago come up with their own version of this philosophy -
K.I.S.S.
Cheers!

 

[m-cman]

There will be two filaments in the bulb. You can inspect and see if either or both are broken. It is easily visible. Sometimes it is intermittent as they are broken but still touching. If they look ok, just gently shake and see if the filaments separate.

 

[jagco1]

This is funny, I had the same thing 3 weeks ago low beam would not work. I check voltage at the head light plug low beam wiring no volts, I trace it back to short about 4" away from the switch. But bulb could out, or not making good contact in in the plug.

 

[Fire-medic]

Thanks, Miles for the referral on Occam's Razor. That has been mentioned on here before too.

How-about Hobson's Choice? Having a non-functional headlight, whatever the cause, is truly a Hobson's Choice.

I had what I thought was a bad switch but was only a burned out or bad beam filament which was actually making intermittent contact & light. Brand-new out of the box too which made me think a bad switch. Now my switch is v. clean though. Sometimes the simplest solution is the correct one.

Hey FM - A tad off topic, but google OCCAM'S RAZOR.
Along the same lines, there is also an old French expression, that loosely translated goes...
"Perfection in design is achieved not when things are added, but when everything not required has been taken away"

Of course north americans, in all their eloquent glory, have long ago come up with their own version of this philosophy -
K.I.S.S.
Cheers!

 

[MaxMidnight]

Is a blown bulb obvious?

Note wishing to sound sarcastic but if a bulb has blown then there will not be any light.
Easiest way to diagnose the issue would be to try a known good bulb.

As stated above it has a twin filament bulb as shown below.

The blue warning light comes on when power is sent to the high beam filament via the yellow wire (and then on to the waning light and then to earth) from the High- Dip beam switch. This is a simple rocker switch that has a single feed in which powers either of the two circuit depending on what is selected.

Whilst I am always happy to bow to the superior knowledge of my peers, I can't see anything in the circuit that would cause the main beam indicator light to come on should dip beam fail. Am I missing something?

 

[WonkoTheSane]

Whilst I am always happy to bow to the superior knowledge of my peers, I can't see anything in the circuit that would cause the main beam indicator light to come on should dip beam fail. Am I missing something?

That's what concerned me. I should obviously check the bulb as well, but wondered if there was anything obvious I could have messed up when doing the rectifier and battery. All responses are greatly appreciated.

 

[MaxMidnight]

...but wondered if there was anything obvious I could have messed up when doing the rectifier and battery.

Unless you have managed to be spectacularly ham-fisted then I suspect not.
Try the bulb first.

It seems reasonable that the warning light would come on when main beam is selected even if the bulb has blown but I can't see why it would stay on with dipped.

 

[WonkoTheSane]

Thanks for all your patience with my ineptitude.

I got a few minutes to pull the headlight today. Nothing looking very wrong with the bulb, except looking a little old.

I put in a new one and switched on and it lit up. Joy!

Except then I switched to full beam and it died again. Not working on high or low beam. I assume something blew it and pull it back out. Not visibly blown.

I put it back in and it's working again. Not blown, then. On closer inspection, the connector is a bit corroded and very dirty. I suspect that repeated removal and insertion cleaned the contact enough to make a better connection. I squirted in some contact cleaner and cleaned up with a bit of abrasive and out the old bulb back in, now working properly again.

Thanks again for tolerating such a n00b. At least I now have a couple of spare bulbs

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[jagco1]

Wow need a good cleaning. Glad it work out for you.

 

[gamorg02]

i haven' tlooked in years but you might be able to unclip the metal pins from that and get a generic headlight plastic connector instead of wasting time cleaning it up.

 

[Bill Seward]

You just might want to take a look at the plug between your stator and voltage regulator, too..... Nasty can o' worms if that one corrodes!