Wiring question.

[jbu]

I'm finally getting to wiring the T3. I purchased a new main harness and am using the old sub-harnesses which are in decent condition. Now for my question.

The bike does not have a kill switch and starter button, but uses the ignition to start the bike just like a car. All of the wiring diagrams I have all have starter buttons and I am getting confused as to what to do.

In the wiring diagrams a white wire goes from the ignition switch through the kill switch to the coil. A black and white wire goes from the starter button to the starter relay.

Now my thought is to connect the white wire that starts from the ignition switch directly to the coil. But That does not get me very far.

Does anybody have any ideas or suggestions?


Thanks, Joël

 

[DanPez]

The bike does not have a kill switch and starter button, but uses the ignition to start the bike just like a car. All of the wiring diagrams I have all have starter buttons and I am getting confused as to what to do.
Thanks, Joël

Do you mean that the key ignition on the bike is spring return?
If so .... that extra 1/4 turn, on the key, is considered your starter contact.
This would be similar to a starter button.

The kill switch is wired in series with the starter switch
In other words ......the kill switch is ON or OFF, starter button is OFF with momentary ON.

Hope it helps

 

[jbu]

Hey Dan,

yes, it is a spring return ignition switch. Does that mean that the wire that is connected to the "starter"/last springed notch of the ignition goes to the coil?

Thanks, Joël

 

[Tonerjockey]

Hey Joel,

I used that starter set up on my Eldo for decades! I liked the ignition switch / key thing.

I never really had a use for a kill switch.

If it works, why bother messing with it?

Alex

 

[jbu]

The problem Alex is that it doesn't work. I like the idea of that set up too. But I don't quite no how to wire it up correctly so that it will work. I have gutted this bike and the wiring is one of the last details and unfortunately I have a hard time understanding it all. I usually just put things back as they were but this bike's wiring was such a mess I had no choice but ignore what was done and focus on wiring diagrams. So now here I am trying to analyze the old wiring harness and compare it to T3 wiring diagrams and my head is ready to explode.

I know everything will work itself in the end as they always do, but I could really use some help here.

Thanks, Joël

 

[moto]

Without being able to see your switch, advice has to be general.

You should have four contacts on your switch, which you will need to identify by using a meter or a small light, or similar means:

Contact A -- from the positive terminal of the battery (and not via a fuse, as I recall)

Contact B -- provides +12v when the ignition switch is in the "On" or "Run" position

Contact C -- provides +12v when you turn the key all the way clockwise and hold it there

Contact D -- provides +12v when key is in the "Park" or "Acc." position

Instructions:

1) Connect contact B to a white wire that goes to the Kill switch and from there on to the coils.

2) Connect contact C to the starter relay wire (I don't recall the color or exact routing, but your wiring diagram would help).

3) Connect contact D to the circuit that leads to the tail (not the stop) light. I believe this circuit is yellow-colored wires on the T3.

Hope this helps.

Moto

 

[DanPez]

Does that mean that the wire that is connected to the "starter"/last springed notch of the ignition goes to the coil?
Thanks, Joël

As Moto mentioned .....
Turning the key once you have ignition ....... power is given to the coil.
What you mentioned above "springed notch" ...... that momentary contact goes to the Starter Solenoid.

Also polarity is important.
Coil needs a +12v ..... on ignition ON.
Starter needs a gnd ...... to engage solenoid.

 

[jbu]

THANK YOU dan and Moto! I'm starting to slowly see the light. I understand that it is extremely difficult to give advice from a far and without diagrams, but feel that you have already helped me understand what needs to be done.

I checked/ tested the switch and identified

-the 'start' wire :contact C
-the on/run position: contact B

I have not been able to tell the difference between contact A and contact D. When I put a continuity light on them it is lit all the time even when the key is out.

I am going to check over my notes to see how it was originally wired and check back later.

Muchas gracias, Joël

 

[moto]

I have not been able to tell the difference between contact A and contact D. When I put a continuity light on them it is lit all the time even when the key is out.

Some (automotive) switches have two positions when the key is turned to the left (counterclockwise). The one all the way to the left is "ACC.", for "accessories." Sometimes the key can be removed in that position, which connects contacts A and D. Try turning the key a little to the right, to the "OFF" position, and then remove it. In that position A and D should not be connected.

Looking at the front (key side) of the switch, the positions in clockwise order, from left to right, should be: ACC -- OFF -- RUN -- START.

I think that you can distinguish A from D by determining which one has continuity with C (Start) when the key held all the way to the right (clockwise). (But it may be that both will have continuity.)

 

[jbu]

Hey Moto,

After fiddling with the switch some more I found the OFF spot where the A and D do not have continuity. It took some doing but the key can be removed from that spot, it takes a bit of fiddling. The key can easily be removed from the counterclockwise position ACC as well.

Unfortunately I still can't seem to tell the difference between the A and D. They both show continuity on all settings except the OFF position.

joël

 

[moto]

Unfortunately I still can't seem to tell the difference between the A and D. They both show continuity on all settings except the OFF position.

As I feared, alas.

There are two possible situations, one where you have correctly found A, and one where A and D are misidentified. Here is the first one, showing the paths of continuity when the key is all the way to the right in the START position:

Situation I.

A ------ B
A ------ C
A ------ D

Connectivity is transitive, so if D is connected to A, then it is connected to B and C via A (barring the presence of diodes in the circuit).

In the second situation A and D are misidentified but nothing inside the switch is changed; only the labels change like this:

Situation II.

"D" ------ B
"D" ------ C
"D" ----- "A"

"A" will still be connected to B and C, with the switch in the START position, because of transitivity. The only practical difference between the two situations is that the connections between the battery and terminals B and C are indirect in the second one, when the battery is hooked up to the misidentified "A" instead of the real A. For example, the connection to terminal B becomes "A" -- "D" -- B, rather than the direct route A -- B.

It is conceivable that you can measure the difference in resistance involved in the two situations, using an ohmmeter. (Or measure the difference in the voltage drop with the circuit under load, using a voltmeter.) The resistance between "A" and B should be higher than between A and B, if it is measurable.

The bike should run in either situation. The only worry involves the possibly greater resistances to be found in the second one. If you can't measure a difference it probably doesn't matter which connection you use. I would try to find evidence as to which terminal took the wire from the battery. Sometimes the way a wire is bent or the markings its terminal left on the switch can tell the tale.

Moto

A -- from the positive terminal of the battery (and not via a fuse, as I recall)
B -- provides +12v when the ignition switch is in the "On" or "Run" position
C -- provides +12v when you turn the key all the way clockwise and hold it there
D -- provides +12v when key is in the "Park" or "Acc." position

 

[jbu]

Thanks Moto. I think I identified the A and D by looking studying the notes taken when tearing apart the bike as well as examining the old wiring harness.

This is where I am now. I am working off of your information as well as a T3 wiring diagram I have on hand.

wire A via rectifier goes to + battery
wire B via inline fuse (not sure what amperage?) to coil
wire C via fuse box to starter relay
wire D via fuse box to lights, horn ect..


How does that sound?

Joël

 

[john zibell]

jbu,

I'm not sure where you are getting the A B C D business for your ignition switch unless it is aftermarket. Stock Guzzi switches have numbered contacts. Take a look at this schematic for an Ambassador https://www.guzzitech.com/guzzi007/s ... 9_V750.gif It is one of the few Guzzis to start with the ignition switch. Very few others started this way. Since you have a T, I'd recommend using a separate starter button/engine cut off switch like this one http://www.mgcycle.com/product_info.php ... ts_id=2592 and following the T schematic.

 

[jbu]

Hi John,

Moto used the ABC and D wiring as a way of clarifying what each wires does and needs to be connected to. It's just a way of simplifying things so that I can make sense of my switch. It has helped me get my head around it.

The bike came with this switch and no start button or kill switch. I wanted to keep it this way if I could. Less clutter on the handlebars.

When I finish wiring it all up with a battery in place I will report back with news (good news, I hope)

Joël

 

[moto]

Thanks Moto. I think I identified the A and D by looking studying the notes taken when tearing apart the bike as well as examining the old wiring harness.

This is where I am now. I am working off of your information as well as a T3 wiring diagram I have on hand.

wire A via rectifier goes to + battery
wire B via inline fuse (not sure what amperage?) to coil
wire C via fuse box to starter relay
wire D via fuse box to lights, horn ect..


How does that sound?

Joël

Hi Joel,

Sorry to have left your question hanging.

Your plan sounds good. I don't think the original wiring had a fuse in the circuit going to the
coils (which surprised me). The original coils are specified as giving 3.35 ohms of resistance
at 20 degrees C, so I suppose a bit more when heated up. Any application of my Sum
Total of Electrical Knowledge uses some combination of the two formulas E = IR and P = EI.
We have E = 12 (volts) and R = 3.35 (ohms). So, using the first formula gives I = E/R = 12/3.35
= 3.58 amps per coil, or 7.2 amps in total. I would try a 15 amp fuse, which should be more than
ample.

Good luck. Looking forward to your report.

Moto

 

[john zibell]

Guzzi did not fuse the coil circuit for a reason. Nothing worse than calling for power to get yourself out of a situation (or a pass) then to have the engine cut out completely due to a blown fuse.

 

[moto]

Guzzi did not fuse the coil circuit for a reason. Nothing worse than calling for power to get yourself out of a situation (or a pass) then to have the engine cut out completely due to a blown fuse.

No doubt you're right. Still, that dodgy kill switch attached to the two unfused white wires snaking through the handlebar looks pretty scary when I think about a short happening there. Choose your poison.

Since our original poster indicates he doesn't want a kill switch, there may be less reason to fit a fuse.

 

[jbu]

I will not be putting a fuse to the coil wire.

I'm still tinkering. It turns out the handlebar controls (lights, horn, blinkers) need some work. I unbound the harness/sheathing of the controls to find that half of the wires were cut and never connected.

I have a green wire that goes from the ignition to the fuse box to a red wire which is suppose to feed my handlebar controls. Well the red wire was not connected to anything. This is probably why nothing seems to work right now.

Joël

 

[jbu]

I'm still working on the wiring without much success . I do have another question in regards to wiring.

Did i wire the starter relay correctly.

30----------30amp fuse---------+battery
87---------------------------------solenoid
86---------------------------------ground
85---------------------------------key switch


thanks,joël