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Quote:
Interesting. I had a couple of new 1157 LED bulbs in my parts bin which I had bought for my small motorhome but have never installed for the reason you mentioned. The socket on the MH rear lamps are vertical and the bulb would be useless unless pointing straight back. I tried them in the Packard and they did not light at all. When tested with the battery using a jumper wire the bulb would light but not at the rear socket. I tested the voltage at the battery, with engine not running, and it was at 6.78 volts and the rear socket was only 5.80. I guess that resistance in the wire (new harness) and the switch reduced the voltage at the light socket below minimum requirement of the bulb. The bulb will light with 6+ volts but not as bright as it will with 12 volt obviously and below 6 volts will not light at all. Bulbs are made specifically for 6 volts.

A similar discussion is currently at the CushmanGroup:

There are LEDs that will work in the 6 to 36 volt range.
Performance is the same in all voltage ranges. You just
have to look for multi volt LEDs...

Jon

On Wed, 12 Aug 2009 13:09:53 -0000
"miscoot52" <jfaltinek98@yahoo.com> wrote:
> Dose anyone know of a 6V LED light that can be used as a
>tail light?
>
> Thanks,
> Joe in Texas
>

If you want brighter bulbs convert it to 12V and leave the 6V bulbs in there. They'll be bright for a few seconds!

Turbopacman wrote,
Quote:

I like your answers. LOL You have a good sense of humor. I wonder how many people will now put 6 volt lights in their 55 and up Packards?

I was reading a previous post in this thread about the almost one volt drop between the battery and the tail lights. That seems way too much. I think either there are bad connections or the wire size is way too small. I think the in line connectors can be dirty and/or corroded causing the excessive voltage drop. I would clean all the connectors and the contacts on the bulb and the socket. A few 10ths here and a few 10ths there and before you know it you have lost a whole volt.

A good ground connection between the engine and the frame of the car is also important.

Quote:
Bob, The wiring is a new factory correct harness installed less than 5 years ago. All connections are clean and bright. There is an additional ground strap from engine to frame. From my experience with adding halogen lights to my moderrn cars a voltage drop of 1 volt is not unusual in fact a drop from 14 volts (alternator voltage) to 11 is common with original wiring on some modern cars. I used relays and 10ga. wiring to rewire the headlights on my Volvo and the same when I installed halogen headlights on the Packard. I suspect that the resistance in the light switch and the long run of wire from front to back is the cause for the voltage drop. If others on this forum would check the terminal voltage on the tail light sockets it might make for some interesting results.

I'm going by the math involved. #10 wire has a resistance of .0009989 ohms per foot. One 6 volt tail light draws 0.8 amps. Four of them in parallel would draw 3.2 amps. The total resistance for 15 feet of #10 wire would be 0.0149835 ohms (15 X .0009989). Ohms law says that the voltage drop in a wire is equal to the current (3.2 amps) times the resistance (0.0149835). 3.2 Amps times 0.0149835 Ohms = 0.0479472 Volts drop. So 6 volts minus the 0.0479472 Volt drop would still leave 5.9520528 volts. If the IR drop is greater than that it is loosing voltage somewhere else besides the wire. What is left are the connectors ( a likely source ) and the switch contacts.

In other words the voltage at the tail lights with 6 volts at the battery and 15 feet of wire would only be maybe a tenth of a volt low not the 1 volt talked about. Any more than that is lost across bad connections or dirty switch contacts nothing else is left.

Just went out and measured the voltage at the tail lights in my 51 and it did read approx 0.5 volt below the terminal voltage of the battery. I must have some bad connections too.

Just thought a one good reason for converting to 12 volts. The voltage loss in a 12 volt system is a smaller percentage of the applied voltage than in a 6 volt system.

Bob, I sincerely want to thank you for doing the math for me and checking your cars tail light voltage! The wire thickness to the tail lights is less than #10 ga. so your formula while valid is not applicable in this case. I was just using that #10 ga as an example for wiring fog lights and headlights which have much less wire run as well. I suspect that the switch and connectors which are 62 years old are the culprits although the incandescent lights are working fine just not the LED bulbs. I will try to clean up the connectors and swicth terminals and see what happens. maybe those LED's will work after all! Ain't physics wonderful?

As a retired scientist, I just love your approach - isn't science wonderful!

Quote:

Owen,
I can't tell if you mean that or are being sarcastic. I am just an old electronics tech. Ohms law is about the first thing I learned as a kid. My Dad was an electronics engineer and taught me a lot from an early age.


Clipper47,
The number for #10 wire may have been a little off.
for #10 wire it's 0.00118 ohms per foot,
#12 wire is 0.0016215 ohms per foot,
#14 wire is 0.0025756 ohms per foot,

For 15 feet of #14 wire and the same 4 tail lights at 3.2 amps (0.0025756 ohms per foot X 15 feet) Times 3.2 amps for 4 bulbs = an IR drop of 0.1236288 volts. 6 volts minus the drop of 0.1236288 volts = 5.8763712 volts at the lights.

Still only a little over one tenth of a volt.

The Voltage drop you specify would be correct for a 15ft run from the source (battery) to the point of testing in a perfect environment. But if you look at the wiring schematic for the Packard there are numerous splices, connectors, circuit breaker, the Light Switch, flasher circuit, bulb base, etc. Add 60+ years of corrosion both to the actual wires, and the all the connection points and switch internals and also figure if you are running at night you also have more load through the switch due to the headlights, dashlights, etc. Now add the quality of the bulb socket ground to the mix.

A volt meter at the bulb socket, using the bulb socket's own ground will tell you how much voltage is actually making it there.