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Old 05-01-2005, 08:14 PM
P.E.Haiges P.E.Haiges is offline
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Join Date: Jan 2000
Location: PA
Posts: 5,440
Jim H,

I agree with every thing you wrote. Light bulbs get dimmer because some of the tungsten filament boils off (that's the dark coating on the inside of the glass) and the filament resistance gets higher. Thus the current gets lower and the filement is a little cooler and gives less light.

I'm not sure GP get higher resistance as they age. All mine seem to have about the same resistance: 0.6 +/- 0.2 ohms. I would be suspicious of readings that were exactly the same as yours are. Did you pull the GP cable connector out of the GP relay when you measured the GP resistance? Since I measure the GP resistance thru the connector's female terminals, I may have read some difference because of the resistance of the wires and the connection to the GP terminals.

I will have to try reading GP resistance at the GP with the cable connector in the GP relay to see if there is any difference.

But all the GP that I found bad were completely "dead" I.E. open circuit equivalant to a burned out light bulb.

P E H
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