Relay oddity

Just thought I'd mention this here for posterity's sake: in the GRiSO parts manual, relay AP8124869 (the big square one) is listed as the injection relay. However on my bike at least it is in fact the start-up maintenance relay (#3 in the wiring schematic: [You must be registered and logged in to see this link.] )

Caused me some confusion.  (Either that or I'm now magically riding without injection   )

edit: There is a second square relay near the taillight part of the bike that I assume is the proper relay for the injectors.

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Is that this one ?

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That's the one. On my bike it's the third relay in the row (front to back) There is actually a second one of those square relays hiding near the taillight, which I assume is the 'real' injector relay.
I just thought I'd post this to prevent some potential confusion since the relay is specifically listed as 'injector relay' in the parts catalog.

Relay AP8124869 has a built in diode in series with the relay coil, I am sure it is there for a reason  

some GRiSO wiring diagram didn't show the diode

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Phang wrote:

Relay AP8124869 has a built in diode in series with the relay coil, I am sure it is there for a reason  

some GRiSO wiring diagram didn't show the diode

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Perhaps. It could also be a budget thing, perhaps the injector relay is cheaper Afaik its just there so you can override the ECU if it doesn't allow the bike to start due to voltage drop. Maybe it has some alternate invisible function though, it does go to the right light switch. Fact is the bike starts and runs just fine even without the start-up maintenance relay installed (I tried).
But yes the wiring schematic I linked doesn't show the diode. Where is your image from that does show it?

But I started this thread mainly because of the confusion it caused me when I had to connect the wiring from the maintenance relay to the wiring of the starter relay after I replaced the solenoid feed wire, as I initially assumed (incorrectly) due to the parts catalog that the big square relay was the injector relay, and the start-up maintenance relay then must be one of the other relays that are identical to the starter relay, which would make sense. Thankfully it was easy to determine this wasn't the case by inspecting the wires themselves, but I can imagine someone making that mistake and splicing the wrong relay wires.

I haven't got the chance to inspect the wiring harness, where exactly are the splices of these two relays?

somewhere here?

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Unfortunately not. The wiring truly is a bit of a mess, in your image roughly after the bend to the left of the starter relay the two thin wires from the maintenance relay that eventually connect to the solenoid feed from the starter relay, are connected to simply thicker wires, but don't yet splice into the wire from the starter relay.
That splice only occurs somewhere near the bottom or even out of view of your image, rather deep inside the wiring loom.

Rather than excavating half the wiring loom I simply cut off the thin maintenance wires where they connected to the thicker wires, and spliced them into the new solenoid feed wire where it connects to the terminal of the starter relay, if that makes sense.

"That's the one. On my bike it's the third relay in the row (front to back) There is actually a second one of those square relays hiding near the taillight, which I assume is the 'real' injector relay.
I just thought I'd post this to prevent some potential confusion since the relay is specifically listed as 'injector relay' in the parts catalog."

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I was trying to fit a MPH startus interuptus kit to my 1200 Sport and found this relay (in the photo), pulled it to make sure it was the starter relay, it disabled the starter only, but had a different plug pattern to the wiring kit. Go back to the computer and to think a little bit.....a couple of days later I found another correct pattern relay hidden well under the tank and only found after the side cover was taken off. The Guzzi wiring diagram only shows 1 relay in the starter circuit - must have been a factory fix to try to eliminate the no start problem ?

Phang wrote:

Relay AP8124869 has a built in diode in series with the relay coil, I am sure it is there for a reason  

some GRiSO wiring diagram didn't show the diode

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The older Guzzis called it the Safety Diode, it prevents powering up the ECU if you put the battery in backwards.
I don't know why they don't have the diode in the loom like the spine frame bikes instead of having a weird relay.
The bike will still crank though it must turn backwards or perhaps the starter clutch slips.

Thanks for the explanation Roy

Actually Phang I may have put you wrong, its usually the ECU or injection relay that has the diode, I cannot see it serving any useful purpose in the maintenance relay but it won't stop it either, my guess it was just handy.

Heres a typical bike from 2000 with the later ECU, the diode (51) is part of the loom
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A later CARC bike with the diode in injection (aka ECU) relay (29)
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Roy, I just look at the wiring diagram again.

Pressing the START button will ground ECU PIN 28

I think the diode in the Maintenance Relay is there to prevent grounding of ECU PIN 28 through the solenoid of the starter motor.

You may be correct.
It's pity they just didn't wire the original relay correctly instead of adding fix on fix.

I suspect adding the diode came after the recall notice when they asked the dealers to remove the second relay.
If you look at the starter wiring over the years you can see the factory has been struggling with it, every time they get close they
go and wire it back through the switch. I came to the conclusion they don't know the solenoid has two coils and it draws 40+ Amps.