Blown Headlights..

Hello everyone..I love my J.D. sled but I can't keep a headlight in it..The factory bulb (AM52959) seems to be a GE-4492, now obsolete. This is a 60W/60W 5.5" (par46) sealed beam. I am using the common H5006 automotive bulb as a replacement. They last less than 2 minutes. Tail light works fine, on all the time, never blows out. The system is 12 VAC, (yes, AC) with a regulator which I checked and seems to be working fine, measured voltage is 12.5 AC, steady as a rock..So why is the headlight burning out so fast? I figure it MUST be vibration, but vibration level seems to be moderate and normal..Or the automotive bulb somehow does not like the AC current. Can someone tell me why the 4492 ($25 each) is so special or am I overlooking something?[/b]

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Does your sled have electric start?? Many older sleds had e-start which usually failed over time so people would take the battery out. The battery acts as a voltage regulator though and without it the voltage will spike burning out headlights. Just an idea :whatever:

Are you touching the bulb...If you touch the bulb your oils from your skin will get on the bulb and cause a hotspot , it will heat up in a matter of minutes and burn out..Make sure you wear clean gloves when changing the bulb .......

I would assume your voltage regulator...if that is bad/disconnected you will blow bulbs almost instantly.
Are you getting 12.5 VAC when it is idling? If so, you're voltage may increase when you rev up the engine. (Light gets brighter when sled revs)

You shouldn't be any problem with the automotive bulb either.

Again, make sure you don't touch the bulb without gloves.

Your voltage regulator may be fine while the wiring to the headlamp may have become separated from the regulator which would cause over-voltage. Make sure you check the headlamp connector voltage and do it at higher rpm - like 3000 or so.

The headlight is a sealed beam, they don't care about touching them..I'm beginning to think the regulator gets hot and "opens" after a minute or two, allowing the voltage to exceed safe limits. The tail light somehow survives.. The "regulator" is actually a big zener diode that sends any voltage over 13 to ground, limiting voltage to that level..Crude but effective. It never had a battery....

I've heard people say that regular automotive lamps cannot take the abuse in off road vehicles. I assume your voltage tests were done at above idle RPM and the voltage was held steady at as the RPM's increased. I don't think the AC voltage is a problem, the lamp filiment shouldn't care. Measure your voltage at the healdight socket after the sled is good and warm and see if the regulator is still regulating.

That's good advise R580..I have been checking the voltage with the machine cold..On this sled, the headlight is on all the time. It has a high/low beam button. The alternator, a single winding, is rated at 120 watts...I'll install a new bulb and monitor the voltage continuously and see what happens..And yes, the voltage sags to 6 or 8 at idle and jumps up to 13VAC with some RPM..But I only checked it for a few seconds..I have the service manual and a wiring diagram, a very simple system, so i hope to get this sorted out. I seldom ride at night, but when you need a light, you need a light! The fact the tail light, wired to the same terminal as the head light, has never failed puzzles me..I've never even looked at the bulb. I think I will. Maybe it's not a standard 1157 automotive bulb..