headlight bulbs

just had a headlight bulb burn out in my 97 ram 4x4 this weekend. i went ahead and replaced both at the same time as usual. as i was logging the
service into my service journal i looked back to see when the last time the bulbs were replaced on this truck. at 275,350 miles and 10+ years of rough service this is the first time i have ever put new headlight bulbs in the truck. i was amazed, the factory bulbs lasted a decade.
i decided to look at the service records on my other dodge trucks. the 2001 3/4 ton 4x4 diesel at 160k is still on the factory bulbs. the 1991 dakota that has 177k known miles (had a broken odometer for a while) is on its 2nd set of bulbs. the 1993 4x4 dakota with 220k is on its 5th set of bulbs. i am now curious as to why the 93 goes through so many more bulbs than the others. any theories? michael
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Most likely, higher system voltage. This will be a product of the voltage regulator on the alternator. You are probably over 14 volts when running. Steve

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Since Power = Volts x Amperes; an increase in the applied voltage will result in a proportionate increase in current, and an increase in the power that is a *product* of the two. An increase in consumed power will cause the filament(s) to burn hotter, and reduce the life of the lamp.
Another factor is the number of on/off cycles. A lamp filament undergoes an extreme change in temperature from off to on, causing a mechanical stress in the filament. These mechanical stresses in the filament decrease the life of the filament.
Bryan
Steve Lusardi wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Bryan wrote:

"Since Volts = Amperes x Resistance" would make more sense. What you wrote has volts and current on the same side of the equation.

Punkin, a.a.d.t's resident electrical engineer, taught us that blue light is brighter than yellow light! Therefore, we can turn down the juice and just tint the glass blue.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

You are both correct, kinda sorta. For the purpose of this discussion however, Bryan is uisng the "correct" interpretation of Mr. Ohm's law. Since the resistance of the bulb's filament is a "constant" in this case, the question (variable) is the voltage which ultimately determines the current and thus the filament temperature which if too high will result in an early failure.

That's a discussion for another day.
Mike
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

No, come on Mike, lets hear it.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Mike Simmons wrote:

Both of Georg Ohm's expressions are true. I was solving for E (volts) using P (watts) and I (current/amperes). Ohm's pie and a nifty calculator is here: http://www.the12volt.com/ohm/ohmslaw.asp
Another way of tracking the consumed power (assuming the resistance of the load doesn't change appreciably) would be to use: P = I^2 x R or P = E^2 / R
The only trouble is, AFIK, no lamp manufacturer specifies lifetime vs power consumption. However, suffice to say it will be less if the specified voltage (and current) is exceeded, and longer if the voltage (and current) is less than specified. There is some mention of lifetime vs applied voltage here: http://tinyurl.com/2opm7l . If concerned, the OP should check the applied voltage with engine running (above idle speed) to verify it is not significantly higher than it should be.
Bryan
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Bryan wrote:

Sorry, he had a 50/50 chance, he picked the wrong equation.

"FYI white or blue light is brighter then yellow." http://groups.google.co.in/group/alt.autos.dodge.trucks/msg/a6a2a718fd5687de

That's NOT what you wrote. You were (weren't) showing that an increase in applied voltage will result in a proportionate increase in current.

Some here don't know that the voltage should be checked across the bulb, while the bulb is in the socket and turned on. They'll take out the bulb, measure 12V at the empty socket, and think it's all bitchen.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

That could be caused by many things. The two primary ones are a loose headlight assembly and / or a voltage problem. If the headlight assembly or the bulb socket is loose, that will cause the bulb to vibrate excessivly which can cause a significant reduction in bulb life. If the regulator is not controlling the voltage properly and either allowing an excessivly high voltage or voltage spikes, that to can cause a significant reduction in bulb life.
--
If at first you don't succeed, you're not cut out for skydiving



Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

    Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.