If it's US specification the lights work when you start the bike or turn on the ignition (on a Mk2)
US bikes don't have an on/off light switch. UK and Europe are different.
With the ignition off you shouldn't get any current across the terminals. If you do, it'll flatten your battery in short order.

Start the bike and see if there's current there (with the fuse in place)- should be 13.5V or more.
If no joy, that's your problem - no fire in the wire
It could be the plug connector, mine did it a couple of times but that won't effect the fuses I don't think.
Let us know how you get on !

 

Thanks! I knew enough to try it with the bike running (the headlight doesn't come on until it starts, IIRC), but tried it with the fuse pulled. I'll try it again with the fuse installed and see if there's voltage.


I'll be sure to let you know if/when something works, and thanks for all the help.

I never knew there was a forum for these bikes; I thought my unnatural love for my '90 CBR1000F was a unique thing!

Thanks,

Larry

 

The DMM will show voltage if one probe is on the fuses and the other is on the negative side of the battery. If you're looking for a broken connection, you should be looking for continuity. Looking through the wiring diagram as far as I can tell it goes: fuse, splits to starter switch and relays, splits to high beam light and hi/lo switch, then bulbs. One relay controls the high beam light on dash, the other controls the low beams

 

Reading Malbojah's post I'm wondering if it's not the Hi/Lo switch ?
They have been known to fail............
Another option to try
FWIW

BTW I run on low beam all the time and the bulbs last about two years and they go within hours of each other. Could it be the filaments in the bulbs ? Maybe check them on a battery to be sure...........

 

No, if you put the VM leads on each side of the fuse ( red on 1 side, black on other) it will not read any voltage if the fuse is good, conversely, if the fuse is bad it will.

But, if you put the black lead to chassis ground, a good fuse will register power on both sides with the red lead, whereas a bad fuse will have power on only one side of the fuse.

I'd be looking at the hi/lo switch. There are 2 relays that control the headlights along with 2 connecting blocks which could also be suspect.

 

I just re-read this, the headlight should turn on as soon as you turn the key to ign. There is a contact in the start button that shuts off the headlight when the starter is engaged, also could be suspect.

So,

Ign switch on, engine off- headlight on

Ign switch on, engine cranking- headlight off

Ign switch on, engine running-headlight on

 

This is a problem with my bike and another old Interceptor I owned. Currently on my 87 1000f the starter button is worn out. Put the headlight on Hi-beam, start the bike. Jiggle the starter button and see if the light comes on. I ride with my light permanently on hi. If I see the dash light lit I know I have a working headlight

 

Gentlemen,

Thank you so VERY much for this help. Armed with your suggestions, I packed my tools and wheeled the bike out,ready to start checking continuity and tracing the fault.

Secure in the belief that, at least for me, it's never the 'easy' fix, I decided to try wiggling the starter switch, just for a chuckle.

Lo and behold, two wiggles and the lights are back! What's more, they *seem* to be fairly reliably back, as several checks with the starter and hi-lo had them staying on.

I would have never thought of that interlock; never, without the suggestion here.

Thanks to all of you for your assistance-you've truly 'made my day', as I'll be riding, rather than wrenching, on my lone day off this week.

Thanks again!

Larry

 

Enjoy your ride

 

Glad to be of help (me and my trusty wiring diagram)