Instrument lights keep burning out

[pckopp]

I replaced every light bulb in both instruments and the bulbs on the center display. I wanted them all to be the same brightness.

Last night coming home after dark I realized I didn't have any instrument lights. Today I pulled the instruments and all the panel lights are burned out. High beam light still works fine as do all the center display lights. These worked for awhile but this was the first time I was out after dark - really dark.

'78 Standard
HHB PMA
Pamco Ignition

Runs great, just did 350 miles over the mountains and back.

Suggestions?

 

[xjwmx]

Whenever I take something apart up there, a bulb quits working shortly thereafter, it seems like. Maybe just disturbing an old bulb causes it. Vibration could probably weaken the filaments. I got replacements at Walmart, which actually had "high brightness" version of a bulb that would fit. It's bright enough to let you see the needle clearly and read the odometer and trip counter.

Make sure you didn't actually put in 6v bulbs, if they're still available. Might be a bad brand of bulb. All burning out at once is telling.

 

[DogBunny]

Replacement LED instrument bulbs are available through eBay, and they are nearly indestructible. They have the added advantage of drawing almost no power to operate.
Other than that, mount a voltmeter where you can see it, so that you can tell if you are over-charging. There have been a few recent threads on cheap, small, simple to-mount voltmeters recently.

 

[pamcopete]

I replaced every light bulb in both instruments and the bulbs on the center display. I wanted them all to be the same brightness.

Last night coming home after dark I realized I didn't have any instrument lights. Today I pulled the instruments and all the panel lights are burned out. High beam light still works fine as do all the center display lights. These worked for awhile but this was the first time I was out after dark - really dark.

'78 Standard
HHB PMA
Pamco Ignition

Runs great, just did 350 miles over the mountains and back.

Suggestions?

The instrument lights are on all the time whereas the center indicators are only on when they have something to report, so if you had a high voltage condition from your PMA regulator / rectifier, it would affect the instrument lights first.

Check the battery or capacitor voltage with the engine running at 3,000 + RPM and wait for the battery to charge to see what the voltage is with out the charging load.

The other remote possibility is that you inadvertently installed 6 Volt bulbs.

Pete

 

[pckopp]

The instrument lights are on all the time whereas the center indicators are only on when they have something to report, so if you had a high voltage condition from your PMA regulator / rectifier, it would affect the instrument lights first.

Yes. Also the taillight which seems not to be affected. Much larger bulb, of course.

Check the battery or capacitor voltage with the engine running at 3,000 + RPM and wait for the battery to charge to see what the voltage is with out the charging load.

I have a little Datel digital unit I use exactly for this. Leads attached directly to the battery.

Battery voltage after sitting overnight: 12.7
Idle voltage: 13.4
3,000 rpm: 14.5 with headlight on, 14.7 with headlight off
Voltage constant well above 3,000 rpm.

The positive and negative leads from the rectifier unit attach directly to the battery terminals. New heavy ground strap from battery to frame.

The other remote possibility is that you inadvertently installed 6 Volt bulbs.

Ah, no.

I have been getting the electrics sorted on this bike for awhile. The main wiring harness is new but the handlebar switches are used. I have cleaned them, the connectors and the connectors to the instruments. It is possible I may have left a connector loose inadvertently in my troubleshooting. I will double-check it all.

The blinkers and turn cancelling work fine, as does the brake monitor and neutral light.

The manual only indicates the instrument lights as 12V 3.4W lights. I bought a box of 10 from a local parts house and that is what all the other lights are. I wouldn't mind if the turn-signal indicators on the dash were a bit less blinding. The rest are fine.

Thanks!

 

[XSLeo]

Often blowing bulbs can be caused by weak grounds. After I rewired my 75 I had a rash of blown headlights. I finally tracked it down to weak grounds. A bit of cleaning and tightening fixed it.
Leo

 

[pckopp]

Often blowing bulbs can be caused by weak grounds. After I rewired my 75 I had a rash of blown headlights. I finally tracked it down to weak grounds. A bit of cleaning and tightening fixed it.

I did find one ground that wasn't as good as I would like. I cleaned it and a little blue stuff for good measure.

All back together.

Thanks everyone.