Tailight Wiring Problem

Well, I've almost finished a 6 year restoration of my 66 bug, but I still have some lingering problems with the wiring. The greatest problem is that the rear turnsignals, brake, and running lights are very dim (you have to take off the lenses to see the filament glow). I just replaced the battery yesterday and the red light on the speedo goes out after ignition, so I'm confident the engine wiring is sound. This afternoon I cleaned the ground strap contacts, as well as the positive battery wire. Each of these lights do function correctly, just very dimly. The most obvious problem occurs when I am driving down a hill and am coming to a stop. As I take the car out of gear and apply the brakes, the engine will often die. Also, in the past the battery has worn down over a number of weeks and has to be trickle charged to get the car started again. My first guess is there is a short somewhere in the wiring (It is the original 40 year old wiring) or I have a poor ground coming from the fenders. Any ideas?

Reply to
anthonyjonas
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I'll assume this is still 6V.

In '66, the only ground for the tail lights was thru the fender bolts and the 2 tiny screws holding the tail light housing to the fender!

Get a voltmeter. Even a cheapie. Measure voltage from chassis/engine case to the tail light wire. If that is 5-6V, the wiring is OK. NOW...measure from the brass shell of the bulb/socket to the tail light wire. If less than the 5-6V, the ground is bad.

Old wiring doesn't just "go bad". Yes, the crimped ends may get corroded, but that can be fixed if need be.

NEXT...use your voltmeter to see what the battery/Gen is doing. Put the meter across the battery posts. Rev engine (requires long arms:-) and voltage should jump up to 6.8 to 7.2V . If it does, the Gen is working correctly.

NOW...remove the battery NEG (ground) cable. Turn the key off and Interior light and anything else that might be on. Set the meter to Milliamp scale. Connect meter RED lead to the ground strap you removed from battery. Connect meter BLK lead to the battery NEG post. If the meter reads ~50 milliamp or less, there is no "short" or draw on the battery.

Speedy Jim

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Reply to
Speedy Jim

did someone put 12 volt bulbs in? Weird but could happen. more than clean grounds. run new wire grounds. check the ground on the trans-axle to frame. Or better yet, run a new ground cable from the engine to the frame or directly to the battery. good luck. We always go to 12 volt.

Reply to
A Veteran for Peace

Sorry but i do disagree on that one, IF it is still 6V I'd keep it that way. It is possible to have a proper electric circuit with 6V, it just needs more maintenance/attention. Mine is 6V too and don't wanna change it at all. Of course mine isn't a daily driver and i like it all stock...

Roger

Reply to
bug '59

Thanks all, those are some good suggestions. Unfortunately, it started raining today (it IS Seattle), so I'll have to put off troubleshooting until Friday. I'll give you all an update then. In regards to the 12V conversion, I have considered it for safety reasons so I could install HID headlights, LCD cluster tailights, and other such electrics that would keep people from running into me. Of course, I've done the entire restoration as a "back to original" job and a 12V conversion wouldn't really be in the spirit of that. Since the car is just a Sunday driver, i'm leaning towards keeping it 6V. Plus those dim little headlights do grow on you!

Tony

Reply to
JonasBone

Well, the sky cleared for a few minutes so I pulled the bug out and ran the tests. The voltage coming from the hot wire in the tail running light is 4.8V The same voltage applies to the ground test.

The battery voltage across the posts is 6.2V. When the engine is revved, it jumps up to 7.2

For the short test, with the key out of the ignition, I was unable to find any milliampres being drawn, with the key in RUN position, but with the engine off, it was pulling plenty of amps.

Where should I go from here?

Reply to
JonasBone

Supplementary Note:

The tail running light, turn signal, and brake light all work when only one of the three is on at once. However, during my voltage testing I noticed that the running light was lit, even when the fixture was not in the housing (no ground). I assume the same would happen with the brake light, but I didn't have another body around to push the brake , while I watched. With the tail light fixture ungrounded, I disconnected the turn signal wire at the tail light fixture, and the running light lost it's power. In addition, when I had the car idling with the headlights/running lights on, and the turn signal on, the engine would lose power in time with the turn signal flash. This backs up my earlier story of how the car would often stall when coming to a stop at the bottom of a hill, since I would normally have the turn signal on while my brakes are on. Following my (often faulty) logic, it seems that while the brake light and running light do have a correct ground back to the battery, they are also grounding out back through the turn signal wire.

Since I'm a poor electrician, any advice on how to confirm/cure this problem would be much appreciated.

Reply to
JonasBone

Everything sounds pretty much normal. Battery is charging correctly. There is no "phantom" drain. Tail light voltage is about what I would expect.

You could follow the path to the tail lights and measure the voltage at each point. Headlight switch Both sides of fuse(s)

Speedy Jim

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Reply to
Speedy Jim

Ah. Interesting clues.

Put your meter from chassis to the first fuse. Put it on the side of the fuse which has the Blk wire from the Ign switch. See what the voltage does when the turn signals are on. This terminal feeds the Coil as well.

If you see significant voltage drop, I would suspect the Headlight switch as one possible. On '66 cars, ALL battery power up front goes THRU the headlight switch terminals. Often, they overheat and cause voltage drop.

In any event, use your meter to find out where the drop occurs. Start back at the Coil maybe to verify that voltage does drop when signals are on. I don't think the stalling is caused by the tail light.

Speedy Jim

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Reply to
Speedy Jim

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