Tail Light Assembly

[Dr Gil]

While everything is "in the mail" pertaining to my timing cover I thought I'd deal with the electrics in the rear section.

 

During the crash of my '02 Le Mans I slid tail first for quite a ways (200 feet). The tail section took the brunt of the slide. Prior to the crash the previous owner had wired two sets of LED lights into the brakes...I never cared for the looks of it but it worked fine.

 

Fast forward to present time. Everything was pretty much a shambles in the tail section. I've replaced most everything. I have new turnsignals (Buell) and can get the license plate light and tail light to work...but still no brake light.

 

There are only 3 wires to deal with (plus an extra off of what I assume is the brake wire (gray) for the second LED off of the "red/blue" wire) so how hard can it be? Electrics are not my thing (still trying to sort out what IS my thing).

 

Two of the connections are side by each (see pic) on the back of the light. Running lights (yellow and black)? Why two? Why do I have a yellow wire and it doesn't show in the wiring diagram? The connection off to the side seems to be the brake light. If I connect a running light wire to it it goes into bright, "brake" mode.

 

 

I have turnsignals working and can get the tail "running" light and license plate light working with the configuration in the photo...but no brake lights.

 

Should I be looking for the problem to be elsewhere? Broken wire? It appears that the Le Mans has two brake micro switches. Am I correct in (again assuming...dangerous) that even if one switch was damaged in the crash (neither was impacted by the left-hand side slide) I would still get a brake light from the other one...so it is probably NOT a switch that's goofing me up?

 

Geeze, I hate electrics.

[Ouiji Veck]

Ewww boy...

I'm the last person to help ya here Doc.

I fially got a new set of headers for my Bella Bambina and was

ready to rejoin my friends on our monthly vintage tours when I noticed

the brake light wasn't working...that was 2 yrs. ago!!!

I had the head light BLINKING before I was through....

I decided I was going to break iit comepletly down again (engine on the bench)

and give it the final build and ride it into my sunset years...but I got no room

in my 20X12 garage and the other 2 kids always need something...something small

then I can ride....the Ducs got to go ...or a couple more years and I can ride that with the Bonnies and slash/ bikes

I bet there'sa wiring expert here somewhere...I'll be watching...cutting and pasting too

I bet.

[Guest ratchethack]

Am I correct in (again assuming...dangerous) that even if one switch was damaged in the crash (neither was impacted by the left-hand side slide) I would still get a brake light from the other one...so it is probably NOT a switch that's goofing me up?

Gil, your assumption is correct. In the event that one switch was damaged, or if its ability to operate properly was otherwise compromised, operation of the other SHOULD still give you a functioning brake light.

 

However, after being knocked around in a crash before discovering no brake light, it would probably be unwise to assume that either brake light switch is now capable of function, since both could have been disabled. You need to check them both.

 

It's not just the electrical operation of the switches that you want to verify, but the mechanical adjustment that makes each operate. From what we know about your crash, this is more likely to be the culprit than a malfunction of the switches themselves IMHO.

 

You should be able to hear a faint *click* at each switch with application of each brake. This would tell you that the mechanical adjustment of each switch is at least within operating range and that the switches are mechanically operating.

 

I hope you have some kind of a voltage and/or continuity tester - DMM, DVM, or at least one of those cheapo automotive electrical probes with a 12 v. bulb and alligator-clip wire to test with? If not, now's the time to get one. Since you have a long-range ownership objective here, I'd recommend a quality DMM or DVM.

 

The next step would be to make sure you have voltage between the "live" side of each switch with the key in the "on" position and ground. If this checks out, I'd then test for voltage at the "switched" side of each brake light switch with the brake on.

 

If this checks out, I'd then follow each of the switched wires (front and rear), checking for voltage to the taillight. There are many connectors along the way. If you have voltage on the "switched" side of each switch when each brake light switch is on, but not at the taillight, you have a break in continuity in the wire between the switch and the taillight. Each connector is a potential point of failure and something to suspect. Cycling each connector, crimping lightly, and filling with dielectric grease are all good procedure.

 

Hope this helps.

[docc]

Certainly sounds like switches or a bad connection. The tail section conceals some bullet connectors for the tail/brake/winkers. This is a good time to carefully pull them one at a time with good needle nose, dielectric grease and be sur they are tight going back together.

 

The switches are notorious for getting cruddy. Clean them both with a good electrical contact cleaner.

 

Use a test light to check for juice along the circuit. These are cheap and reliable with a probe one one end where the handle cotains a light and alligator clip on the other end.

 

Light:

 

No light:

[macguzzi]

Certainly sounds like switches or a bad connection. The tail section conceals some bullet connectors for the tail/brake/winkers. This is a good time to carefully pull them one at a time with good needle nose, dielectric grease and be sur they are tight going back together.

 

The switches are notorious for getting cruddy. Clean them both with a good electrical contact cleaner.

 

Use a test light to check for juice along the circuit. These are cheap and reliable with a probe one one end where the handle cotains a light and alligator clip on the other end.

 

Light: 

 

No light: 

70228[/snapback]

Your problem is the black wire is earth, yours is not connected to earth, the earth connection is the one on the side. Yellow if I remember is rear light and blue/red is brake if not it's the other way, but these should be on the central connectos, what is that grey wire and where does it go?

[Martin Barrett]

Your problem is the black wire is earth, yours is not connected to earth, the earth connection is the one on the side. Yellow if I remember is rear light and blue/red is brake if not it's the other way, but these should be on the central connectos, what is that grey wire and where does it go?

70234[/snapback]

 

Mac,

1)- the red/blue is his brake and the grey was a spur to a second set bulb when he had twin LED's.

 

2)-Are you saying his earth and brake are connected the wrong way around? To the wrong terminals. I'll brave the fog and look at mine.

 

Edit - Quick look is no good, will need to take it apart a bit. Can't do it now as home alone with the 3 youngest, so can't disappear outside. I'll have a look tomorrow in daylight if the rain stays off. Bike is still living outside

Edited December 10, 2005 by Martin Barrett

[luhbo]

Your problem is the black wire is earth, yours is not connected to earth, the earth connection is the one on the side. Yellow if I remember is rear light and blue/red is brake if not it's the other way, but these should be on the central connectos, what is that grey wire and where does it go?

70234[/snapback]

 

So it looks, indeed. Switch the red with the black one and check wether it works. If it works better but still not perfect, switch red with yellow.

 

Do you have a multimeter at hand? If not you'd definitely buy one. It's probably not your last electric action once you've got the taste of it.

 

BTW, if you start thinking about things like "why do I have a yellow cable there, the book says grey here" then you've already got track of the bigger mysticisms of italian bikes

 

hubert

[Guest ratchethack]

Your problem is the black wire is earth, yours is not connected to earth, the earth connection is the one on the side.

Confirmed. Mac was spot-on. It's been a year since I had looked at my taillight wires and I couldn't remember the terminal setup or wire color codes. But just now I was able to get continuity between the side terminal (black wire) and ground by accessing it from the reflector side after taking the red lens off.

 

So as Hubert said, just switch the red-blue with the black and you should be in business...

 

Gil, looks like you might be able to hold my above brakelight troubleshooting post "in abeyance", as they say (somewhere - Texas?)...

[Dr Gil]

Confirmed.  Mac was spot-on.  It's been a year since I had looked at my taillight wires and I couldn't remember the terminal setup or wire color codes.  But just now I was able to get continuity between the side terminal (black wire) and ground by accessing it from the reflector side after taking the red lens off.

 

So as Hubert said, just switch the red-blue with the black and you should be in business...

 

Gil, looks like you might be able to hold my above brakelight troubleshooting post "in abeyance", as they say (somewhere - Texas?)...

70247[/snapback]

 

Jeeze, do I feel like a dope on that one

 

I thought I had tried every possible combination of the three wires. I switched the black and red and bingo! Running lights AND a rear brake light...but alas, no front brake light. At least I'm on the right track now. It's freezing in my garage right now so I'm done for the day but tomorrow I'll persue it further.

 

Thanks All!

[macguzzi]

Jeeze, do I feel like a dope on that one

 

I thought I had tried every possible combination of the three wires.  I switched the black and red and bingo!  Running lights AND a rear brake light...but alas, no front brake light.  At least I'm on the right track now.  It's freezing in my garage right now so I'm done for the day but tomorrow I'll persue it further.

 

Thanks All! 

70252[/snapback]

Any wiring I can usually help with, I've been buggering around with Guzzi wiring for 30 years, it aint got no better!

[Dr Gil]

Things warmed up enough today today to the point where I could get back into my tumbledown (unheated) garage.

 

I spent a few minutes "bonding" with my Le Mans and then started sorting out the "no brake light" on the front brake problem. It didn't take long to discover that one of those teeny-tiny connections at the front switch (at the front brake lever) had slipped off. Dielectric grease on everything including all the connections that have been made in the tail section so far and I'm happy to announce ALL of my lights are now working as they should!

 

I can't say I love all this wrenching on the bike and I'm envious of those who have the availability of a decent Guzzi shop but there are times, few and far between I'm afraid, when the sense of accomplishment and the joy of seeing something finally work after all the toil and trouble is intense. This was one of them.

 

Thank you all for your help. I couldn't have done it without you ...now tht that's done I'll see you over in my other thread about the timing cover...after it arrives).

 

Till then, chill awhile, smoke 'em it you got 'em.

[Guest ratchethack]

...there are times, few and far between I'm afraid, when the sense of accomplishment and the joy of seeing something finally work after all the toil and trouble is intense.  This was one of them. 

Careful, Doc. If you keep this kind of thing up, it won't be long before other Guzzisti will be envious of YOU, 'cause you'll have at long last broken ENTIRELY FREE of your (potentially) unhealthy dependency on a far-away, unknown shop...except for spares, of course. As it should be, IMHO - BAA TJM, & YMMV.

Thank you all for your help. 

Por nada. It's the gestalt of the Forum experience that brings benefit to all. ...and to all, a Good Night...