Wiring loom for a T3

Making a wiring loom for a T3
I’m in the process of restoring a pretty standard T3. It arrived in boxes about 30 years ago…and I’ve finally got round to it. Can anyone help me with the following questions:

  1. Are there any occasions, apart from the starter cable and the battery earth strap, where the cabling is anything other that 16.5 amp/1mm?
  2. According to the wiring diagram borrowed from Gregory Bender’s site there is no fuse between the battery and the ignition key. Is this a good practice?
  3. I am using a Lucas Rita system that requires the 6 volt coils to be connected in series. Is there a wiring diagram out there for this?
    Thanks in advance to anyone who can help.

Should be able to find original Rita instructions on the Internet.

Just connect + of one coil to - of the other, it’s literally just a short link. Then the free + goes to kill switch (white wire?), and the opposite free - goes to ignition amplifier.

Yes no fuses between battery and ignition switch or even for the ignition circuit.

Although Carl Allison’s wiring diagrams (on Gregory Bender’s site) are generally very good there are some discrepancies that I have found between them and Moto Guzzi workshop manual diagrams. Blue wires are sometimes shown brown, as in the feed to the T3 front brake light switch and brown wires are sometimes shown black as in the feed to the T3 horns. I have prepared my own drawings for these bikes with the errors I have spotted corrected, pdf copies are free to MGCGB members.

I think the errors have come about because the source material is in Italian and the colour names Nero = black, Marrone = brown and Azzurro = blue may have been unfamiliar. I have also noted differences on some of his other wiring diagrams where Bianco = white is confused with Marrone = brown. I cannot be sure that there are not any other errors and would suggest that you confirm any that you are not sure about with the Moto Guzzi workshop manual diagrams.

Good luck!

Don’t follow the original wiring with the starter relay, or you will be having starting problems within a few months.
Feed the centre terminal direct from one of the lower fuse ways that are fed direct from the battery and not through the ignition switch.

Take the wire to the centre terminal of the relay (The other red one is going to the solenoid) .


Wiring diagram sent

Regards Chris

I’ve done this. Those spare fuses are useful for it.

On a Spada one fuse feeds the clock and the other the hazzards, both require permanent feed so are not through the ignition switch, but on a T3 there are not these accessories and so these fuses are not used and not connected directly to the battery. Ignore the advice above unless you want to run your own direct feed to one of these fuses.

Quite right may have to make a link to make them live - think I had to do that on the LM.

I just bought a replacement loom for my T3 Cali from Stein Dinse. It is a cinch to fit. I laid it alongside the old loom and simply swapped from one to the other, connector by connector.