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Relay Failures


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#1 dlaing

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Posted 10 October 2003 - 07:20 AM

Eureka!
I think I discovered a major cause of the relay failures on our bikes.
About two years ago I replaced the relays on my bike with the grey Bosch units.
Over the past month or two they started to fail.
I ordered a new set from Dan Prunuske, and he took interest as to why the relay failed
so I decided to investigate the cause.
Looking at the wiring diagram on Carl Allison's site and looking at the specs on the relays, I realized that the current of the headlight and a few other current using devices passed through a 10 Amp rated section of the relay!!!! Drat! The Guzzi Engineers made a mistake!!!!
But being an electrical layman, I was not completely sure, so I emailed a reply to Dan, and he agrees that there is a problem.
He posted the following on the MGCL:

From: Dan Prunuske
Date: Thu Oct 9, 2003 8:58:48 PM US/Pacific
To: MGCL@topica.com
Subject: V11 Sport Wiring vs Relays

Dave Laing recently contacted me regarding a failed Bosch starter relay on his V11 Sport. He thought the problem was that the Normally Closed terminal of the starter relay powered the headlights, not merely the coil of the headlight relay. I was skeptical (who would be so stupid?), but after checking the wiring diagram, he is correct. Worse, that terminal (rated at 10 amps) also powers the brake lights, the tach, the horn, some of the instrument lights, and is the reference voltage for the GEN lite! Arrrrgh. The high beam and the brake lights alone are about 9 amps, and imho, too much load on a 10 amp contact. (My normal rule of thumb is to use a relay capable of twice the anticipated load).

So you ask, what controls the headlight relay? The stupid sidestand safety switch! Arrrgh. Nice going Guzzi. There is no horn relay - full current goes thru the switch. Loverly. Another buck saved.

What to do? I'd suggest:

1. Install a horn relay. It's tolerable that this relay's coil is powered thru the headlight relay, but it's horn current should come from a fuse, not from the headlight relay.

2. Remove the white/green wire from terminal 87a of the starter relay and run it instead to Fuse 5 (this is the headlight power). Disconnect the orange/blue wire from terminal 85 of the headlight relay. Run a wire from terminal 85 of the headlight relay to terminal 87a of the starter relay. Now the only load on terminal 87a (the Normally Closed terminal) of the starter relay will be the coil for the headlight relay. The difference is now the headlight will still operate if the sidestand is down.

Edit 10/12/03 Forget this option.(2.) After posting this, we discovered that it will not work....so go with option one or something else, like a higher rated relay, or a strategically wired additional relay.
Until you fix this issue, avoid using the horn and the high beam flasher.
And for what it is worth, the headlight is not deactivated by the kick stand switch.

No doubt there are other improvements that could be made to this crappy wiring layout. For example, I'd be inclined to get at least the brake lights out of the headlight circuit. My mods suggested above should greatly extend the life of the starter relay. BTW, they are made on the assumption that the bike is actually wired as shown on the diagram. Bwa, ha, ha!

Carl, may I presume that terminal 86 of the headlight relay is grounded? It's not shown as such on your diagram.

Does anyone know which other relays on this model seem failure prone?

Cheers,
Dan


Carl then replied that the presumption is correct about the relay being grounded through terminal 86.
Obviously people are getting by with the wiring done as Guzzi layed it out.
But if you want a reliable machine, I recommend doing one of the modifications that Dan suggested.
Does anyone have any other ideas, suggestions, or questions regarding the relays?
What other relays are failure prone?
I seem to recall that some would not start because of the relays.

#2 Guest_russ_*

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Posted 10 October 2003 - 03:02 PM

Great stuff! Way to go MG :moon:

#3 jrt

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Posted 10 October 2003 - 03:48 PM

Maybe :moon: to Moto Guzzi, but :thumbsup: to Dave, Dan and Carl. Way to go!
J

#4 Guest_captain nemo_*

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Posted 10 October 2003 - 04:31 PM

I knew I needed something new to worry about - especially something electrical for which I know absolutely nothing. :homer:

I am anxious to see some of you make these changes and report back. I am hoping that even a Homer Guzzisto can manage it. Today I am installing my new K&N pods and firing it up. We'll see if it even starts.

#5 gthyni

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Posted 10 October 2003 - 04:54 PM

I don't remember the side stand switching off the head light.
In fact I think I lost power to start the bike by accidently
leaving the head light on while taking a break.

Maybe there are diffences in wiring between diffent years or
between my euro-guzzi and your "american goose".

#6 dlaing

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Posted 10 October 2003 - 05:11 PM

I don't remember the side stand switching off the head light.
In fact I think I lost power to start the bike by accidently
leaving the head light on while taking a break.

Maybe there are diffences in wiring between diffent years or
between my euro-guzzi and your "american goose".

I don't remember that either.
But then again we almost always put the side stand up when the key is on.
There could be a difference between models, and the wiring diagram probably has errors.

#7 IanJ

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Posted 10 October 2003 - 07:40 PM

I don't have my Le Mans with me right now or I'd check, but I'm nearly positive that my headlight is not controlled by the side-stand switch. I have a 2002 red/grey Le Mans. I think the headlight is only controlled by the ignition switch, on my bike.

#8 al_roethlisberger

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Posted 10 October 2003 - 10:15 PM

My headlight is *definitely* not affected by the side-stand being up or down.

So maybe later bikes are wired differently? I don't have time to go check right now, but someone with a later bike might want to go out and see if the wires and their arrangement described by Dan are in fact different on the first gen bikes versus later years :huh2:

al

#9 dlaing

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Posted 11 October 2003 - 04:08 AM

Regarding the headlight going off with the kickstand down, I think Dan mis-read it, due to more errors on the diagram.
So, hold your plans for modifying the wiring.
I stared at the wiring diagram for a bit and now my brain hurts. :huh:

#10 Kiwi Dave

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Posted 11 October 2003 - 11:28 PM

Only guessing, but I think the headlight would be controlled by the starter relay (i.e. a relay that is closed when the starter switch is activated). This would allow all the juice from the battery available for the starter motor.

My headlight on a New Zealand 02 Le Mans definitely stays on, regardless of the sidestand switch. My understanding is the sidestand switch in conjunction with the neutral switch and the clutch sensor controlls the ignition circuit only.

One day I might investigate further, but I leave well alone that seems to be working fine. :rolleyes:

#11 dlaing

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Posted 12 October 2003 - 08:57 AM

Only guessing, but I think the headlight would be controlled by the starter relay (i.e. a relay that is closed when the starter switch is activated). This would allow all the juice from the battery available for the starter motor.

My headlight on a New Zealand 02 Le Mans definitely stays on, regardless of the sidestand switch. My understanding is the sidestand switch in conjunction with the neutral switch and the clutch sensor controlls the ignition circuit only.

One day I might investigate further, but I leave well alone that seems to be working fine. :rolleyes:

You are correct. The headlight relay is controlled by the starter relay which sends current to the headlight relay whenever the starter is not activated and it is done to allow more power to the starter. Unfortunately all the juice going to the headlight, brake/taillight, tachometer, and horn flow through a ten amp rated section of the relay. The same section is fused for 15Amps!
The clutch switch allows the starter relay to activate.
The sidestand switch in conjunction with the neutral switch control electricity to the starter, the fuel petcock, the ECU relay, and the ignition relay.

I edited the initial post as follows
Edit 10/12/03 Forget this option.(2.) After posting this, we discovered that it will not work....so go with option one or something else, like a higher rated relay, or a strategically wired additional relay.
Until you fix this issue, avoid using the horn and the high beam flasher.
And for what it is worth, the headlight is not deactivated by the kick stand switch.

My last set of Bosch relays lasted for probably 15,000 miles, your mileage may vary and they are cheap enough that you could replace them regularly, so that is another option, but for optimal reliability, a fix is in order.
A relay activated by the lighting relay and getting power from the #5 fuse, should do the trick.
FWIW I have used the horn maybe four times, and the headlight flasher maybe fifty times.
If you do not use the horn and flasher, your amperage should be under 10 Amps and all should be fine....I think.

#12 dlaing

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Posted 04 November 2003 - 07:29 PM

Some good news!
Dan P. searched and searched and appears to have found a suitable replacement relay.
Instead of being rated at the Bosch's 20A/10A it is rated at 25A/20A and should fit right in the socket.
Dan will send me one to try out.
If it fits, I'll give it thumbs up.
Of course the real proof is a few years down the road.... :bike:

#13 al_roethlisberger

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Posted 05 November 2003 - 01:20 AM

Excellent, let us know... and if it works, I'll take two :P Heck, maybe one should just replace them all with the "tougher" model?? Why not? :huh2:


Even though my horns no longer load that circuit(other than to trip the new horn relay)... better safe than sorry ^_^

al

#14 Guest_captain nemo_*

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Posted 05 November 2003 - 02:44 AM

Yes, I'll take a batch. If the components handle it, it is an easy solution.

#15 dlaing

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Posted 05 November 2003 - 05:46 PM

I was curious as to what is the most miles someone has on their relays without a failure.
I can't remember when exactly I replaced my mine.
I guess it took 15,000 miles for it to fail.
Has anyone gone further?
If so, do you use your horn or flasher?




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