Clock Bulb

[BigLou]

I removed my 280SL's original clock for quartz conversion (works great) and took the opportunity to replace the bulb, which was a 12913 K5614 Phillips 12v2w. I think this is a BA7s bulb. I replaced it with a 12v2w bulb that must be a BA9s because it fit very tight, and the bayonets sat on the lip of the bulb cylinder rather than inside it. I reinstalled the clock (and the radio, through which I accessed the clock), and everything was perfect, until the next morning. The battery was so dead, all I got was a click when I attempted to start the car. Headlights showed no current, and instrument lights only glowed slightly. But the clock was still keeping perfect time. The battery is several years old, but has never given a moment's trouble. I had not started the car in about two weeks, but all lights worked perfectly when I reinstalled the clock with the new bulb. Perhaps the battery's time was up, but the coincidence of it being discharged the day after I installed the converted clock with new bulb is hard to ignore. Could the new bulb, by touching the lip of the cylinder, cause a short that drained the battery overnight? Do I focus on the bulb or the battery? Thanks for your help.

[Paul & Dolly]

Hi Lou

Remove selected fuses and see if the problem is resolved.

Fuse No 1 powers the clock and other items.
Fuse No 7 powers the dashboard lighting (incl clock lamp)

Good luck

Paul

[BigLou]

Thanks Paul. Very logical. The time has come for me to buy a battery charger. Best regards, Louis

[Pawel66]

If I may: just to be sure you can measure power consumption by the new clock by connecting a multimeter in series. Then a simple calculation will tell you what power it is consuming in relation to battery capacity.

[BigLou]

Hi Pawel66. Not sure I understand, but one of my sons-in-law is an engineer, and he should understand. Thanks.

[BigLou]

The rest of the story: I bought a charger, and it took only 30 seconds for the battery to register fully charged. I checked the voltage, which was 13.7. Maybe the battery had recovered. I reinstalled the battery and turned on the lights. I still had no headlights, and the instrument lights barely glowed. That made no sense with a fully charged battery measuring 13.7 volts. I measured the voltage with the light switch on and got 7 volts. Aha! A bad battery. I replaced it last evening, and all is well this morning. Conclusion: the old battery died, and it was a coincidence that I had just installed the converted clock with new ba9s bulb. I'll be checking the battery again this evening, and I hope I'll not have anything more to report. By the way, can anyone explain how a battery could register "full" on a new charger, 13.7 volts on a voltmeter, and still be bad?

[Pawel66]

Hi Pawel66. Not sure I understand, but one of my sons-in-law is an engineer, and he should understand. Thanks.

Well, when we have circuit or device suspected of consuming too much power and causing battery go flat overnight or over some time, a couple of days, we can check what is the power consumption.

You set your multimeter for Amps DC. You initially set the range high, say even 10Amps. Then you would disconnect power supply wire from clock. You connect one connector of the multimeter to that wire, the other one to the connector in the clock. You probably and hopefully do not really get the reading at 10Amps range, so you go down with the range until you get a reading.

Then, say your reading is 500 mili Amps (500 mA), which is 0.5A, your clock will consume 5 Ah (Amps hours) over 10 hours (0.5A x 10hours). So it would discharge 50Ah battery over 100 hours - when the car is sitting in the garage for 2.5 days. If your battery was old it might have had just a portion of the original capacity - maybe 10 or 20Ah.

I have no idea what is the nominal power consumption of a Pgoda clock - probably to be found on this forum.

[BigLou]

Great explanation. Thanks!