mgs
[Top] [All Lists]

## Re: Dim Panel Lights

 To: larryhoy@mcione.com, jack@lucent.com, paul.hunt1@virgin.net Re: Dim Panel Lights DANMAS Thu, 30 Apr 1998 19:49:34 EDT
 ```In a message dated 4/30/98 1:53:07 PM Eastern Daylight Time, larryhoy@mcione.com writes: > Lamps labeled 1449 are 14v / 2.8w / .20a > Lamps labeled 1446 are 12v / 2.4w / .20a > (You'll have to ask the "Master" to see if that works with ohms law) Larry, Till the "Master" gets here, will you settle for the opinions of Masters, Dan Masters, that is! First of all, a reminder. You don't have 12 volts in your car if your electrical system is up to snuff -- you have *around* 14 volts as long as the engine is above idle speed (just so we are comparing apples to apples, let's assume exactly 14 volts). That means all devices -- lights, wipers, horn, etc -- are fed 14 volts. At 14 volts, the 1446 bulb will draw 0.23 amps, and dissipate 3.2 watts. A bulb rated at 2.2 watts at 12 volts will draw 0.18 amps when supplied with 12 volts. When supplied with 14 volts, the same bulb will draw 0.21 amps, and dissipate 2.9 watts. I don't have his original post, but if I remember correctly, Jack said a #52 bulb was rated 2.2 watts at 12 volts, while a #53 bulb is rated at 2.2 watts at 14 volts. If that is correct, I offer the following summary: At the normal automobile voltage of 14 volts -- #52 0.21 amps 2.9 watts #53 0.16 amps 2.2 watts 1146 0.23 amps 3.2 watts 1149 0.20 amps 2.8 watts Thus, a #1146 bulb will generate 45% more heat and light than a #53, 10% more than a #52, and 14% more than a #1149. The additional light is very welcome, but I'm not so sure about the heat. The bulb housing in the gauges is quite small, so heat can be a problem. Evidently, though, if they have worked all these years with a #52 bulb, then I don't think the extra 10% will cause a problem. You may want to check my math (my math is OK, but sometimes I get confused and use the wrong data in the equations). Also, a couple of other things to keep in mind. 1) these numbers are approximate, 2) A 20% increase in voltage does not cause a 20% increase in current in a light bulb. As the temperature of the element goes up, the resistance also goes up. Using the data supplied, the resistance of a #1146 bulb at 12 volts is 60 ohms. I used 60 ohms in the calculations above, but the actual resistance at 14 volts will be more, so the wattage and current will be less than shown in the calculations. How much difference, I don't know. That data is just not readily available. Dan Masters, Alcoa, TN '71 TR6---------3000mile/year driver, fully restored '71 TR6---------undergoing full restoration and Ford 5.0 V8 insertion - see: http://www.sky.net/~boballen/mg/Masters/ '74 MGBGT---3000mile/year driver, original condition - slated for a V8 soon '68 MGBGT---organ donor for the '74 ```
 Current Thread Dim Panel Lights, Feldman, Jack (Jack) Re: Dim Panel Lights, JMerz140 RE: Dim Panel Lights, Feldman, Jack (Jack) Re: Dim Panel Lights, Paul Hunt Re: Dim Panel Lights, DANMAS RE: Dim Panel Lights, Feldman, Jack (Jack) RE: Dim Panel Lights, Larry Hoy RE: Dim Panel Lights, Feldman, Jack (Jack) RE: Dim Panel Lights, Larry Hoy Re: Dim Panel Lights, DANMAS <= RE: Dim Panel Lights, Larry Hoy Re: Dim Panel Lights, DANMAS