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Loom Big Connector Question

Discussion in 'Sport Touring' started by Martin D, May 9, 2018.

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    #1 Martin D, May 9, 2018
    Last edited by a moderator: Sep 25, 2018
  2. Normally, the wires in the big connectors are numbered on the wiring diagram, or there may be a detail in the manual showing each wire and its position in the connector.
    The actual connector will then have these numbers cast into the moulding so they can be identified.
    Once you know the “pin” position of the wire you suspect, you can then troubleshoot it further.
     
  3. Sounds like an idea, rather than trying to sort out connecting two bastardised loom halves!
     
  4. I got fed up of problems with "the big connector" caused by corroded connections. It is almost entirely watertight - once the water gets in, it never comes out again! I chopped the whole lot (both sides of the plug/socket) off entirely and soldered the wires instead. Haven't had a problem since. It takes a bit of time and care - in typical Italian style the wires going in are almost all different colours to the wires corresponding coming out...
     
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  5. My 1999 ST4 - and yes, sadly the electrics can become a total nightmare :(
     
  6. could be many things, some as listed already - another is the small wires going into the fuelpump assy going open-circuit. Sometimes this is plain to see when the rubber boot is removed but can occur anywhere on wire run.
     
  7. For all it's "character", the electrics on my Laverda are FAR better quality than on my ST - but they are Bosch :)
     
  8. Martin, have you got good voltage on the battery? Have you tried replacing the ignition and fuel pump relays?
    The issue on the loom variations is probably that looms do change over the years and what is a loom for a MY04 bike could have been a loom for a previous version that was a 2004 registered bike. For example later 748s have different looms with different plug configurations on the main loom connector and are not fully interchangeable with older versions. If you don't really know the model year variances/change year you wont necessarily know what you are buying/selling

    Anyway on your plug if there are issues other than a broken wire in the loom you should be able to see issues by carefully checking the plug contacts. If there is a problem it is usually on the earth paths (there are two both with black wires both sides) which usually show as overheated or burnt contacts
     
  9. Martin the front loom(s) all take an earth path to the battery through two pins in the main plug, if there are problems that is where they usually occur as they carry current from everything atthe front of the bile (lights, idiot lights and clocks) all the time and if dirty or loose will overheat. usual sign of a failure is intermittent clocks and idiot lights but on the later bikes like yours or 749/999 the effect is more random. Similar issue affects all the 916/996/998/748 range. Within the plug trace the black wires or if you have the circuit diagram (and good eyesight) your can identify them from their pin designations which are marked on the plug faces(very small alfa numeric characters), however if they are burnt or overheated it is obvious. If you have to splice around the plug those are the circuits that need doing first. Both sides of the plug (pin and socket) need to be carefully checked and then sprayed with a contact cleaner/preserver/sealer (not wd40). Also, as stated previously, water does get in and can't get out so it is sensible to separate and clean that plug anyway.
     
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