Date: Thu, 31 Aug 00 16:07:37 GMT From: amesnopsamrak.demon.co.uk (Andrew Stephenson) Subject: Re: Saab 1999 9-5 Headlights
In article <39ADBBA3.7886740nopsamcom> mweinopsamcom "Four Weis" writes: > Believe it or not, under-current will also shorten the life of a halogen > light bulb. The Volvo V70 series also had a problem with burned out > lights, but this was attributed to a poor design of the sockets which > allowed the bulb to bounce around. My Saab 900 also burned out one > headlight bulb a year for the 16 years I owned it, while my Volvo 245 > has only need two headlights replaced in 18 years. Could there be some > relationship to the stiffness of the suspension bulb burnout? The > filament would get bounced around more in the Saabs because of the > suspension. The hologen bulb effect I did not know about. (Why should that be? AFAIK, the halogen compound is only included in a bulb to increase vapour pressure, so the filament can be run at a higher temperature, so it becomes more efficient at producing visible light (compared with heat). The increased VP "bounces back" more filament metal ions, which would otherwise fly off and gradually allow the filament to waste away and eventually break.) The vibration is entirely understandable. Odd things can happen when bits bounce around. One could, say, hit the bulb's resonant frequency at certain road speeds, leading to damaging knocks and jolts. (Very much BTW: apparently, in the old days, when a big gun fired on a warship, it was common for signal lamps to break in the gun turret, due to the jolt, so they kept lots of spares handy. What saved the spares, I don't know. <g>) But if this really is the problem with SAABs, their clever bods should be doing something about it. I'd say that having a main bulb go, under possibly difficult circumstances, matters more to the caring motorist than, say, alloy wheels or whether the doors have leather inserts. -- Andrew Stephenson
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