Brake lights are out

[jrt]

OK, so I preface this by saying that I usually perform a 'preflight' check on my bikes, and make sure the lights and brake lights, etc. work. That said, I was in a hurry to get all my bikes inspected here in Missouri (not necessary in Iowa) and I was on the fourth bike- the V11 sport.

I drove it down to the inspection station, where the nice Russian mechanic looked it over and asked how many more of these weird Italian bikes I was going to bring down. Then he started laughing because I had brought down a '74, '81, '02, and now an '01 and they all had the same engine.

He thought it was a very Russian strategy.

Anyhow, He just gives it a quick look-over ('tires ok, no leaks- it'll be fine') and gets the sticker out. Then he remembers that he needs to check the brake lights, so put on the brake....and nothing. No front brake light and no rear brake light. We replaced the bulb and nothing.

His response was 'I already have sticker out. You just go and fix, ok?'

'That's ok with me.'

I drove it home and checked the basics- bulb, the fuses, the relays. All are fine. Cleaned the bulb contacts. Checked all the wiring connectors. Everything was fine. I removed the rear carapace, and all the crap to remove the light housing because I thought maybe a wire came loose there- no dice- the wires were in place. Well, I took the opportunity to check and grease the connections under the fuse block and various other places.

Turns out the brake light was kind of working- on the rear brake, with no bulb, it would pass 12 V to the lamp housing. Put a bulb in it and there isn't enough current (voltage dropped to about 3-4 V). Nothing from the front brake switch. I measured the resistance across the rear brake switch (a few 10's of ohms) and the front (about the same). So it seemed that the switches were working. I thought there was a supply problem and was thinking of ways to supply more current-

Then I did one experiment too many. Bypassing either switch with a small wire lit the brake just fine. WTF? Even though both switches pass current (a few milliamps from the voltmeter), maybe they don't pass enough current for the 60 W bulb ? Did BOTH switches fail at the same time? They were both working the last time I rode it. I repeat- WTF?

Tomorrow or Friday, when I have some time, I'll run a hot wire straight to each switch and see what kind of voltage drop I get across them. I may need to replace both of them...it certainly looks that way right now. Any other ideas? I might as well entertain them while I have everything taken down. Are there any connectors underneath the gas tank that I should look at? I am having a hard time believing that two switches failed at or close to the same time.

[dlaing]

WTF!?!

Check to see if headlight is working, if not, likely a bad relay.

Disconnect headlight and see if that gives you enough additional power.

Could also be regulator is on fritz and sucking out the mojo.

See if problem occurs with engine running and engine off.

See what else might not be working, high beam, low beam, horn, etc.

that is the probably useless wake of my brainstorm

EDIT Oh yah and my taillight went out many times and I kept reseating it and cleaning contacts, but it became a repetitive pain, so I bought a new taillight at the Harley dealer, problem solved, but looking at John A's post below, replacing the socket could have been a solution.

[Mike Stewart]

My thoughts of using a DVM when dealing with bulbs, throw them out! Use a test light which draws current. I have been fooled way too many times when using a DVM when measuring voltage. A poor ground or a single strand of wire will show you battery voltage with a DVM but will not light a bulb. Learned this way back in ??? on my 63 Chevy pick um up.... Yep, poor ground Humm, same technology as the Guzzi

 

Mike

[docc]

Those sockets have a reputation for being pretty weak. Once the soft contacts on the bulb wear down from the vibration (which is amplifed hanging at the back of the subframe) the connection is very poor.

 

Seems like I was able to get a probe in the socket and bend the connections out a little. Adding a dab of copper antiseize paste is good.

 

Also, change to a new bulb with fresh contacts. The 'long life' or Euro style bulbs have an eliptical contact that protrudes more.

[John A]

I put a relay on the brake light on most Guzzi's,been doing it for years and it's been reliable.Makes the switches last longer and gives a slightly brighter light.Plastic sockets will melt over time and the contacts move around so I convert them to metal.There are a million different metal sockets so I look for one that is plain without flanges.The best way I've found to prepare the Guzzi light is to heat a 1/4" drive deep socket that is a little smaller than the new metal light socket and push it through.Then with a sharp knife trim off the melted stuff that you don't need and then I use a die grinder or Dremel to finish fit. too tight and it may crack.Then epoxy or Jb weld the new socket in place.

[jrt]

Hey folks, thanks for the advices.

John, you're hardcore! Not sure I want to replace the bulb housing- this one looks in very good shape. I have it completely out and I can see the contacts. There's no oxidation on anything- I keep this bike fairly clean and dry.

Dave- I pretty well know it's not relays or fuse. It was my first thought, but I tried spares of both and no change. No need either, since I'm getting voltage at one lead. Docc, I've already got the Euro style bulb.

I'll run some more tests tomorrow; today has been hectic. I'm really thinking it's the switches, but I'm just having a hard time accepting that emotionally. I'll run a test light across both switches to check for sure....

[docc]

Both switches gone south? That's like your wife and girlfriend both leaving you at the same time. . .

 

Well, it's been known to happen. Poor bastard then, ya . . .

[dlaing]

Both switches gone south? That's like your wife and girlfriend both leaving you at the same time. . .

 

Well, it's been known to happen. Poor bastard then, ya . . .

...but on a serious note, any chance the front switch lost the bearing???

You should hear a gentle click when activating the brake.

FWIW I have had to replace both the front brake switch and the stop lamp.

I'll bet that front switch would last a lot longer if it activated a relay and not a 20+ Watt bulb.

I think John A. makes a good suggestion for both the relay and the metal socket.

[callison]

Did you check the resistance for the socket to ground?

[jrt]

Carl- good call- yes, I checked it. I have the whole tail light assembly out and I've been tracing all the wires. Thanks again from (another) one of the many happy users of your wiring diagrams.

 

Dave- the ball is still in there. I can hear the click of the switch. I've had it out before to clean it up and yes, I adjusted it correctly.

 

Docc- yeah.

 

Maybe I will put in a relay. Now that I have the seat, tailpiece, etc. off, it would be easy to run the wires. Somebody needs to buy this bike. Well, as soon as I have the lights sorted.

[mike wilson]

I measured the resistance across the rear brake switch (a few 10's of ohms) and the front (about the same).

 

If this is the resistance when the switch is closed (light on) then it is bad. There should be as close to zero resistance as possible. 10's of Ohms is a no-go.

[jrt]

You're correct Mike. I had at first attributed it to the cheapo DVM I was using. The rear switch actually does read 0 Ohms when closed- but.....

 

It's definitive- both (!) switches are bad. I passed a good hot line through each switch and checked them with a test bulb, which only dimly light. So, they probably have dirty points from arcing or something like that (I'm conjecturing). Anyhow, a quick chat with the boys at MGCycle, and $35 worth of new switches are on the way. I'm now going to take John's sage advice and wire in a relay, and wire up the headlight through relays as well a la Gary Cheek. I've been putting that one off, but in light of this issue, I think it is well worth the effort.

 

 

Thanks for the help and advice, ya'll.

[docc]

Jason, Show us how you end up wiring in the relay. I'm guessing you can activate one relay with either switch.

 

I've already added four relays, a circuit breaker and three fuses to the Sport. Surely there's room for one more.

[DeBenGuzzi]

you check your fuses there Jason?

 

 

I had this problem that my tail lights were out and only the brake lights came on but not full strength so it had current for some reason, the running lights have their own fuse they share with the dial lights. just a thought. I almost took my LED's OUT of their housing to buy new ones and it turned out to be a 25cent fuse.

 

if I'm right I'm so going to laugh at you. just so you know.

 

at least then I wouldn't be alone.

[John A]

JRT what I like to do for a power source is add 2 or 3 automatic reset circuit breakers as close to the battery as possible and run a super well insulated feed wire from the battery + to them.Then you have power for about anthing you want to run.Of course the real deal would be to have a feeder CB bolted right on the battery + but I havn't found a small enough one yet.