Tail light issue!

[lakecountrydave]

Thanks to this board I am so close I can taste it, but yet still so far away I am just about ready to fill the crank case with fresh oil and the fuel tank with liquid gold and hope, but I am having electrical issues.

My tail light will not come on. I have 10.5V at the tail light wire (blue) wire where it connects to the tail light. My brake light (yellow wire) works properly. I can switch the blue and yellow wires and light the tail light filament with the brake.

I am returning the bike back to the road having completely striped her and painted the frame. As I have reassembled her I have cleaned every single connection and coated them all in dielectric grease. The bike is (and has been) connected to a battery tender.

Oddly, last night when I first started trying to figure this out I took the tail light off. At that time the light came on and worked as it should. I went to put the tail light back on and the light stopped working. It has not even flickered since. Currently the tail light is off. I have re-cleaned all the connections on the taillight including the spade connector inside the taillight for the black wire (ground). I thought the rear connector on that harness was the issue so I chopped my harness and spliced the blue wire from just before the rear harness to the light, and like I said I have 10.5V at the end of the blue wire. I have also changed the bulb.

What am I missing?

The other electrical issue that I have yet to work on is that the front signals do not blink (running light work as do the rear signals) I only mention it as I don't think the problems are related, but like I said I don't think

[MaximPhil]

Hi Dave,
I will take the easy question Most of our indicators do not blink unless the bike is running so yours might be " normal" if one can use such a term in relation to an XS
Phil

[lakecountrydave]

Thanks Phil! I was trying to get everything tidied up before I tried to start her, but I guess I will alter my plans

[Yard Dogg]

Is it possible you have a bare spot in the blue wire rubbing somewhere? Maybe going over a sharp edge? If it has looms, it could be in the looms also rubbing on the ground wire.

[bikerphil]

You have a 79 Special, check the connector at the LCU light checker unit, the pins get loose/corrode. This bad connection would affect only the tail light and not the brake light. I recently had this problem, I tightened up the pin sockets in the plug and that fixed it.

[lakecountrydave]

Yard Dogg - By wire loom do you mean the harness? I must say that I have a very limited knowledge of trouble shooting vehicle electrical systems, but let me tell you my thoughts. I have power (the 10.5v increased to 10.7 after I started the bike) right up to where it connects to the tail light. Also, I am pretty sure that the tail and brake lights share the same ground (3 wires - 1 black), and the brake light works. I could definitely be reading the schematics wrong. I also tried another tail light that I had lying around with the exact same results. Clearly, I am looking at this wrong because in my mind the light should work. It has power and ground.

I also thought that maybe the it grounds through the fender as the black wire connects to the tail light housing with a spade connector. So, I clamped the housing to seat hold downs where the paint has rubbed off with the battery charger clamp. The battery charger is still working so I assume I am making a good ground. This did not improve my results.

Phil - how do I tighten the pins? All of the wires seem secure, but I know that doesn't mean that they are. Is there a way to test to see if this is my issue?

Oh yeah, back to the good news - SHE RUNS!!! And the clutch seems to be working

[lakecountrydave]

Phil - I found your testing instructions here:

http://www.xs11.com/forum/showthread...light=test+lcu

Back to the garage!

[Yard Dogg]

You said you re-crimped at the tail light then it stopped working when you put it back on the bike. I've had the exact same problem before. Here's a few things it could be. It may be a dirty bulb socket. Your bulb may not be making good connection on the pole for the tail light in the socket. Since your ground wire does share both tail and brake, I wouldn't focus on that. It must be the blue wire. You said you re-spliced at the light already. I recommend always soldering, but don't worry about it for now. The blue wire starts at the ignition switch, runs through the fuse panel, then straight into the other blue wire that goes to your tail light.

If you can rule out that the socket is not to blame and the connections are not loosing contact (soldering ensures this) then move up to the connector on the blue wire that connects to the main harness. Sometimes old wires will corrode inside the crimp and into the protector jacket. If I see wire strands that are corroded inside the wire jacket after I strip the sheath, I replace them. Honestly, it's the 10.7 volts part that worries me. I like to see 12v. I am thinking you probably have hidden corrosion inside your wires or wire crimps, do you know what I mean?

On any old vehicle, you will have to re-wire and trouble shoot certain things. Whenever I get an old project, I pull the wiring, replace what I can, solder everything, weather proof, etc... I am anal about faulty wiring and absolutely hate roadside wire fixes.

[bikerphil]

Dave, the connector on the LCU uses round pins instead of the blade type pins. First, clean the pins and their sockets with contact cleaner spray. Then take a small jewelers screwdriver and pry against the sides of the sockets to close up the gap. It's not the pins that get loose, it's the sockets that can get stretched out. To test to see if this is the problem, wiggle the wires at the connector and check for the running light flickering on and off (with the key on). When you are finished servicing the connector, coat the inside with some dielectric grease before plugging back together.

BTW, the LCU unit is found on the 79 Special only, it's used with the single tail light bulb, all other models have dual tail light bulbs.

[lakecountrydave]

It looks like Phil nailed the problem I spent several hours last night, and then again this morning trying to remove my left side cover (after checking the connections in my turn signal cancelling unit (it was late ) with no success. However, I was finally able to squeeze the LCU out from behind the locked cover. Moving the connection illuminates the tail light.

Madd Dog - Now you have me concerned about the corrosion in my wires. I am not quite sure what I can do about that, but one issue at a time Honestly, I hope it is a combination of not making a good connection while testing, testing while tired and my cheap GB multimeter. Probably not, but I can at least hope

I just came in to reread the instructions for repairing the LCU connector, and I thought I would post an update.

Thank you both for all the help!!!

[natemoen]

I just came in to reread the instructions for repairing the LCU connector

I think the best repair would be removal!!!

if it really was a good idea way was the '79 the only model to have it......something to think about.

[bikerphil]

if it really was a good idea why was the '79 the only model to have it......something to think about.

The 79 Special only has one bulb in the tail light, if it burns out , the LCU would warn you to fix it so you wouldn't get hit from behind at night time. All the other models have two bulbs, if one burns out, you would still have another one. That's the only reason I can think of.

Glad you found the problem Dave.

[lakecountrydave]

I have to admit that I was leaning towards Natmoen's suggestion. As I did not need a light to tell me that my tail light was out Actually, I was going to cut the connector out and replace it with bullet connectors, but I was short one bullet connector of the proper size. I finally figured out that Phil was instructing me to slide the tool between the plastic connector and the socket, and not into the socket itself. That worked perfectly, and makes far more sense Another plus is that I discovered that I had a very, very small screw driver set that I had forgotten about

Off to reinstall the tail light, and move onto the next issue! I appreciate the assistance, and I have a feeling I will be starting a new post titled something like "F-ing Turn Signals" very soon

[bikerphil]

the front signals do not blink (running light work as do the rear signals) I only mention it as I don't think the problems are related, but like I said I don't think

The Specials do not have front running lights in the signals, only the standards. They should have just one power wire and the ground is thru the stalk. The front lights should be off unless they are blinking when the turn signals are applied. Check in the headlight bucket to see where they are plugged into. Also make sure there are one filliment bulbs (1156) installed.