Headlight bulb burning out quickly

[mitchell]

Hi all. My headlight bulb blew last week and I finally found one locally but the low beam burns out the moment I switch on. The hi beam will burn out after about 10 seconds. So, I've gone through 2 new bulbs in less than a minute. With no bulb in place, the ammeter will just slightly go towards the negative when I turn on the switch. Does this mean the handlebar switch is bad?
All the wiring inside the case looks good, no broken or exposed wires. The harness and switch were brand new a year ago.
1972 bullet 350 standard.
Any thoughts?
 And, something I noticed during my rides in India is that a halogen bulb burns out really fast too. Is halogen just too much for our systems to handle?

Thanks,
Mitchell

[Bullet.wagon]

I would check the voltage at the plug in. Maybe the voltage regulator is not funtioning causing higher than normal volts.

[mikail gransee]

I ordered some bulbs for my 500 and had same prob then checked them and found out they all were rated for a 6 volt system.    . I have a 12. Over charging could also be your prob specially on the "new" models that have a feed wire right from the stator.

[mitchell]

Mikail, all the bulbs are indeed 12 volt. So that is not the problem...if only it would be that easy!
BW, I will borrow a tester and see if the voltage is constant.
Just when you think all is working right, something else comes up to boggle the mind. We Enfield riders must be masochists, no?

[barenekd]

Don't forget to check the grounding, too. A bad ground can cause problems.
You might want to buy a Multimeter. You can get a decent one for $20.00. You will probably need it on a few occasions with an Enfield.
Bare

[mrunderhill1975a]

I had the same problem, it was the small voltage regulator under the seat.

[mitchell]

I have the 2 in 1 combo of the reg/rect .
I did have the 2 seperate. Is there any preference over which to use? ie, are 2 better than one?
Also, since my battery remains charged, could this problem be something other than the regulator?  All other lights work fine too and the wiring all looks great everywhere.

[mrunderhill1975a]

Do you have a 3-wire alternator or a 4-wire alternator?

[Chasfield]

Yeah, if you have four wire alternator your headlamp bulb will be running off a separate regulated AC circuit, independent of the main 12 volt harness. So it can can have over volt faults even though everything else on the bike works fine.

[mitchell]

Took my bike to a local shop and they confirmed that it was the diode/s in the rectifier portion which was not functioning properly.
I pulled the old one off today and found that it was glued to the backside of the left tool box. No mounting screw used. Could this be a reason for it's short life span?
If it is, I am open to some ideas on where to mount the new one. I'm thinking it has to be bolted to the frame, no?

[mikail gransee]

I think it needs to be bolted for grounding reasons and in a open place to air cool it.  GLUED...ha. ha. Talk about cutting corners.   

[mrunderhill1975a]

That could be the problem, you could just buy a new rectifier from RE dealer or you could build one yourself using Radio Shack or Malpin bridge diode.  I did this myself, the factory rectifier seems to be prone to failure in my experience, while the regulator is bullet proof.  The Radio Shack or Malpin bridge diode has worked on my bike for seven or eight years now.  Jim Downey pointed me in this direction and I quote: "A typical motorcycle alternator puts out about 8-10 amps. Radio Shack offers a full wave bridge rectifier* (part number 276-1185) that is rated at 25 amps and it will withstand up to 50 volts, much more than any bike will put out."  See the attached photo. The photo makes the wiring look complicated but in reality it is quite simple to build.  The two white and green wires with the yellow tags are the alternating current from alternator.  The orange wire is the positive to the regulator and the battery.  The black wire is the negative to the regulator and the battery.  I used the heat sink from the old rectifier and attached the bridge diode with a bolt to ground.

[mitchell]

I bought a new combination one at a local shop. The reliable owner said it is heavy duty. I made a bracket to mount it on which will span under the seat using the two seat mount bolts for ground.
I will use a good-quality trailer light connector to hook up to the system.
I will find out tomorrow if it works.
Thanx all

[mitchell]

Well I replaced the reg/rect, added a mounting bracket, rewired, added a new bulb and...pop. Another bulb bites the dust.
The white flag is up.
I have done all I can do with my knowledge. I see no breaks in the line anywhere.
Any ideas greatly appreciated.
Thanx

[Arizoni]

Do you have a volt/ohm meter?
It would be interesting to see what the voltage reading is between the headlight wire and ground.

I'm not sure what to do with the reading but there might be someone here who would take a look at it and say, "Whoe!  That's the old waveflux problem which is easily fixed by parking your bike headed North."  or something like that.