Thank you Morley, yeah it's gone on a walk about for sure! I just ordered another from Amazon, will be here tomorrow (probably late). I just didn't need the frustration of trying to find the darn thing on top of the bike's issue.

If you're like me, the missing charger will appear 5 minutes after you start using the new one! 

Hard to remember without photos, but I'm pretty sure that model has 3 wires to the taillight?  You confirmed it has power and swapped the lights so it's not super likely all the light fixtures and bulbs were bad.

I'd check the black wire that goes forward in the taillight harness and make sure it has a good ground. 

Hi Mark, yep I have thought of that too - I will find the charger once the new one has arrived (it's out for delivery).

It does have three wires, yellow, blue (or it looks blue) and of course black. I have decided that I need to pull the tank, seat and whatever else to find any and all grounds and ensure they are making good contact. I'm just taking a mental break waiting for the charger then I'll dig back in.

I do appreciate yours and others time/thoughts on helping!

I want to try to explain something about electricity and connections that used to trip me up a lot...  you can have "continuity" but with insufficient "flow".

Meters take very little power from the circuit...  so you can show perfect voltage when the wire is not under load.  Most test lights don't pull much power either.  But when the electricity needs to "flow"... like current to light up a taillight...  high resistance to flow in the wires or grounds can drop that voltage to nothing.

Water in pipes is often easier to visualize than electricity in wires and in many cases behaves the same way. 

Electrical voltage is similar to water pressure.

Electrical current (amps) is similar to water flow.

So imagine two pieces of 3/4" water pipe connected with a coupling that only has a 1/8" opening for the water to pass through.  When the water isn't flowing the pressure in the pipe, even past that 1/8" restriction, will be the same as the inlet pressure.  But if you try to get full flow through that pipe, the pressure past the restriction will drop to zero.

You can actually feel this by turning on a water faucet really low so it just drips out of the end of a garden hose...  there will be virtually zero pressure coming out of the hose, just drips.  Now put your thumb over the end of the hose.  If the supply pressure before the faucet is 60 psi, the pressure at your thumb will slowly build up to 60 psi. Take your thumb off the end of the hose to allow the water to flow and pressure after the faucet restriction drops to zero again.

Electricity flowing through wires works in much the same way!  (The biggest difference is electricity is more "instant")

First, think of that 1/8" restriction in the pipe coupler as "resistance"...  which with wiring is a bad or corroded connection, too small a wire, or even a wire with most of the strands broken inside the insulation. 

When you disconnect a wire and check the voltage at that wire, there is no significant electricity flow...  it's exactly like holding your thumb on the end of the garden hose...  voltage (pressure) will be the same as the battery voltage.  Now connect that wire to something that requires some amps (flow).  If there is significant resistance in the power wires or grounds, the voltage (pressure) will drop past that restriction, just like the water pressure when you took your thumb off the hose.  If the restriction is bad enough, the voltage will be virtually zero at the load drawing the amps... a bulb, for example. 

Hopefully making sense so far?  So let me try to explain how you can use this knowledge to troubleshoot. 

First is to realize this "high resistance" can be within the battery itself!  A battery with no load on it can show 6+ volts with a meter connected across the positive and negative terminals.  Now turn on a load (i.e.taillight) and watch the voltage.  Voltage might drop a tiny bit or it might drop several volts.  Sometimes it will even drop to zero across the terminals!  If you have a significant voltage drop at the battery with meter connected directly to the battery terminals themselves, the battery is bad.   (Note that the meter needs to be connected to the actual lead terminals) 

Say battery voltage stays steady.  Now you can leave the meter connected to the negative terminal and start probing the wire connections in the circuit with the load still turned on.  I usually start probing as close to load as I can...  keep in mind you need to leave the wires connected and carefully probe under the little rubber boot if a bullet connector for example.  If you probe near the taillight you should get near battery volts (pressure). 

So going back to our restricted water pipe analogy...  if you connect a pressure gauge (voltmeter) before the restriction, it will read at or near supply pressure (battery voltage)...  but check the pressure (voltage) after the restriction and it will drop after the restriction if there is water flow (amps) moving through the pipe (wire).

So now you can probe the power wire and find the point (or points) where the voltage is dropping before it gets to the light bulb.  For example, if you probe the connection nearest the light and get 2 volts (or a 4 volt loss if battery is at 6 volts), that means the resistance is somewhere between that point and the battery.  So now you check the connection under the seat and have 6 volts (remember light has to be connected).  That tells you the high resistance is somewhere between the connection under the seat and the connection at the light. 

You simply work your way along the wire until you find the area(s) where the voltage is dropping. 

In your case, it sounds like it might be a bad ground if I understand what you said correctly.  I use a similar principle to find bad grounds.  If you have the meter still connected to the negative terminal, you start probing the ground circuit for the light with the light on. Meter should stay at zero.  If you measure battery voltage at the light ground, it means it's trying to ground through the meter = BAD ground.  So you probe the ground wire connections always looking for zero on the meter...   again I start at the load (light) and go backwards along the ground wire..

Reading back through this makes my head spin so next post will be less "theory" and describe the process I'd use.



 

Wow MarkT, you've put a lot into that post. I'm halfway through & got interupted but is super interesting with ways of looking at electrical flow I'd never realy thought of as makes my head spin. I just look for smoke lol but too late by then usually. I'll read on tonight. Thanks for the post.

I'm going to say "meter" (voltmeter) in the following because it can troubleshoot "dimming" better and shows exactly what is happening better...  but you can often use a test light instead of a voltmeter.  Also, I didn't mention obvious visual inspections like a bulb socket that looks like it spent the last 10 years on the bottom of the ocean.  Obvious visual problems like corrosion should be addressed first.

The whole process below is done with one meter probe connected to the negative battery terminal...  process shouldn't take long but you can periodically test for good voltage at battery...  it only takes a second so I usually do this every step.

Step one: connect meter across battery terminals to check battery voltage.  Should read a little over 6 volts.  (If not, obviously you need to fix that first.)
Then I'd turn on the taillight while checking the battery voltage.  If voltage at battery drops significantly, battery is likely bad. 

Step 2: Remove taillight lens and bulb. Turn key to "lights on" position. Leave meter connected to negative terminal of battery and carefully probe terminals in bulb socket.  If battery voltage is present, go to step 3.
No or low voltage? Then I'd start working backwards along the power wire circuit looking for voltage at each connection along the way until I find the "disconnect" or major voltage drop.  See Step 2a below.

Step 3: Install tested/known good bulb.  Wiggle and push bulb gently to see if I can get it to flicker indicating the socket has a bad connection.  (Make sure key is still on in lights on position!)
If light bulb doesn't flicker, touch meter probe to the metal tube the bulb fits into that grounds the metal body of the light bulb.  No voltage? Go to step 4.
If meter reads voltage, there is a bad ground.  Then I'd start working backwards along the ground wire to find the problem.  See Step 3a below.

---

Step 2a:  Only needed if there was no voltage at bulb terminal with bulb removed as described in Step 2 above!  Go to connections where taillight plugs in and see if you have good voltage at blue wire. (Bulb is installed and key is "lights on".)  I'd try to probe under boot carefully to keep load on circuit... but you can disconnect and test and if power, then get under boot and make sure power is still there when connected under load.  If no power, then go to the blue under seat and do the same test.  Then blue coming out of key switch.  Then red coming into key switch.  Again, important to check every connection under load.  

Step 3a:  Only needed if voltage present at taillight ground in Step 3!  Go to connections where taillight plugs in and see if you still have voltage at black wire.  Again, probe under connection boot to keep circuit under load.  If you still have voltage, move to the next connection until you get to frame ground or run a new ground.  When you probe a connection and get no voltage, the problem is between that point and the last point you checked and had voltage. 
Keep in mind the bad ground could even be the battery ground wire to the frame!  

I probably didn't cover every possible scenario...  so ask if you have any questions or just ignore the whole thing if it's too hard to follow.  I have one more method to describe that I developed working on semi-trailer lighting issues.  You have to build a tool, but it can be a real troubleshooting time saver in some cases. 

WOW Mark, that is very helpful and while my head is spinning a little I do believe I understand what your explaining. I'm going to print it out so I have it for reference. THANK YOU!

On another note, the new noco battery charger showed up a bit ago so I have that connected and charging the battery. Thanks again

If anyone is interested I copied this great explanation from Mark to a word document, I will send it to you at your request.

As I said, most test lights don't draw much power and it can be a pain to test under load.  So I built a test light that applied a good load. 

Just take a taillight bulb and solder a length of wire across both terminals...  take another length of wire and solder to the metal bulb housing.  One wire can be a few inches long...  the other should be a couple feet long for a bike.  (I had about 50 feet of wire because trailers were long) When you connect to battery, both filaments will light providing a decent load on the circuit.  

To test the power side, I'd connect the long lead to battery negative and use the short lead to probe the power wire connections until I found the bad connection which I'd know because the bulb wouldn't light past the bad connection but would light before the connection.  I had alligator clips on the wires and used a safety pin to probe. 

To test grounds, I'd hook the long wire to battery positive and then probe ground points and wires...  first test was always probe the frame with the pin and if light wouldn't light, then the ground wire to frame was bad or had a bad connection.  Then I'd probe the light fixture and ground wire.

Technically I didn't need such a long wire but it helped narrow down the issues quickly. 

Probably way too much info but might help someone. 

That too was also helpful but I do have one question, when you said "solder a length of wire across both terminals" so you mean two separate wires?