Hey guys ,
Hershey was awesome , next year I'm going to get there on Monday so I can start shopping the flea on Tuesday , I got there on Thursday at around 9:30 due to Harrisburg rush hour traffic , was not disappointed in anyway , but wished I'd been there earlier in both day and hour , anyhow , picked up a few parts for the Tudor and ordered a couple 6v tail light bulbs from langs as they were sold out , they came in today so I put one in the socket and no light ? Checked with my meter and I'm only getting 3 volts ?? New wiring and headlights work fine , checked connections , 6v at switch but 3 at lamp ?? What am I missing ?? ( other than 3 volts )
Assuming you have the tail lite wire connected to the "tail lite" terminal on the ignition switch, My guess is that you probably don't have a good ground at the rear of the car since there are a lot of painted connections in the ground path. If that isn't it then tell us the year of the car so we can tell you how to do a point by point testing. If you are indeed getting 3 V then the bulb should at least glow a bit. Are you sure it isn't lit at all?
My first thought is that the tail light has a bad ground connection. Check the voltage from the hot wire on the tail light directly to the battery negative terminal. If you see 6 volts then the ground connection to the tail light is bad.
Hmmm. John posted faster than I did!
(Message edited by paulmikeska on October 15, 2015)
The other possibility is that the wire in the car could be too small? Six volt electrical requires a larger gauge wire than twelve volt does. The longer the wire if it is too small? The greater the voltage drop. I have seen 14 and even 16 gauge wire on antiques. That will not work on a 6V tail-lamp because of the length, but might work on the headlamps. Someone please correct me here? I believe that 12 gauge is recommended for six volt automotive lamps. But I often use 10 gauge, especially on tail-lamps.
John R and Paul M are both probably right. A bad ground path is very likely. On a typical antique? There are between six and a dozen points where the ground path can fail. You need to find any and all of them. Ground faults are a cumulative failure and react to not only voltage, but current and load.
Drive carefully, and enjoy, W2
I used #12 wire on all my lights with a dedicated ground for the lights, bright and no more problems. KGB