Lemans 1 switch/ power issues

[Motosan]

Hey, my right handlebar switchgear is acting up on my 78 Lemans. It's original so obviously finicky but I was working fine a couple weeks ago, then I giggled it a bit and now sometimes the bike turns on and sometimes it doesn't. I know people usually put a replacement on it but what are the connections on the inside of the switch? I'm deciding whether to take it off the bar and try to fix it but wanted some advice first. Thanks

[PeteS]

I would first hit with some contact cleaner like Deoxit before rewiring.

Pete

[guzzisteve]

On the inside it is copper contacts & solder. Pretty fussy but can be done if you are used to that sort of work. Again it can melt into muck. I would just put a separate kill switch on it. Black & black/white wires from memory going to a 3 pin connector on headlight.

[Motosan]

On the inside it is copper contacts & solder. Pretty fussy but can be done if you are used to that sort of work. Again it can melt into muck. I would just put a separate kill switch on it. Black & black/white wires from memory going to a 3 pin connector on headlight.

I can solder but can you take the switch apart intuitively? Does it split into two pieces?

[guzzisteve]

Yes, then you'll see if you are comfortable. More like a clam shell.

[blackcat]

As you look at the switch, the left side pulls apart. Just slowly wiggle it as you pull the four pronged plate away from the main body of the switch.

[John A]

Is there springs under the contacts on that one?

[testa_di_formaggio]

If I recall correctly, ground for the starter relay circuit is made inside the switch by a small tab of metal that contacts the handlebar. Of the 3 wires, one is hot power to the Hbar switch, one becomes hot to the coils when the hbar switch is slid to ON, the third is the wire that gives the ground from the handlebar to the starter relay. If you want to check my work, check for continuity from the 3 wire pigtail to one of the terminals on the relay. It's an easy find, your schematic will give you the terminal number. My guess it's the white with black tracer, that shouldn't show hot. One of the two whites ones will. That would be hot from the fusebox with the ignition switch on. My 850 LeMans did the same thing, took the switch apart and right where the little tab was given a surface to make contact with bare metal, there was some rust preventing it. The slightest rotation of the switch would take away the bare metal spot to contact. Switch will pull apart laterally. BE CAREFULL. Miniature springs, tiny pieces, nothing really robust. If that is what is going on, due to cleanable detritus, or that the little metal tab has lost some of it's spring, maybe you can tweek it a bit to give it more tension against the bar.

T d F

[blackcat]

[Motosan]

thanks, thats helpful. I really didn't want to prying things apart without knowing which way. I took a loot at the connections and nothing obviously loose. The wires are so old though so it's hard to know. I guess I'll take it off the handle bar and re solder the connections.

[testa_di_formaggio]

Nice pictures. You won't need to re solder anything is my bet. Once you get it apart, look for the little metal tab on the ("bottom" side in the picture) plastic plate all the wires are soldered to. See if the white/black wire is soldered to the one end of it. Part of that tab needs to cleanly touch the handlebar. Grounds, grounds, grounds.......

T d F

[guzzisteve]

That's the early switch, one i was thinking has colored buttons. Good Luck. You must have found a plastic sleeve on bar? Looks good from here.

[blackcat]

Nice pictures. You won't need to re solder anything is my bet. Once you get it apart, look for the little metal tab on the ("bottom" side in the picture) plastic plate all the wires are soldered to. See if the white/black wire is soldered to the one end of it. Part of that tab needs to cleanly touch the handlebar. Grounds, grounds, grounds.......

T d F

That's what I think it is too. Probably not grounding, but make sure you take it apart over a pan or something to collect the parts and definitely not in a crowded garage.

[Antietam Classic Cycle]

That's what I think it is too. Probably not grounding, but make sure you take it apart over a pan or something to collect the parts and definitely not in a crowded garage.

When I disassemble things that might fly apart, with tiny pieces never to be found, I do it inside of a transparent plastic bag.

[Motosan]

I realized I could take the switch connections out of the housing. I tested them with the molex connections on the other side. All had contact. The tab that touches the bar did have some gunk on it so I cleaned that, hoping that was the culprit but alas it doesn't turn on anymore. Question, if I was getting intermittent power before when I was toggling the switch could it have caused a fuse to blow downstream? Or what would you look at next?

[testa_di_formaggio]

ds

I realized I could take the switch connections out of the housing. I tested them with the molex connections on the other side. All had contact. The tab that touches the bar did have some gunk on it so I cleaned that, hoping that was the culprit but alas it doesn't turn on anymore. Question, if I was getting intermittent power before when I was toggling the switch could it have caused a fuse to blow downstream? Or what would you look at next?

What doesn't turn on anymore? Intermittent power where? Toggling would infer that you are referring to the sliding off/on/off switch. That's just coil power. Nothing to do with triggering the starter. The start button is straight up push. Get out your volt/ohm meter and check it out. If you push the button, and don't get a ground to the relay, start there, work backwards to the switch. If you do, you should also be getting power from the relay to the red hot trigger wire to the solenoid. If not, then work backwards to the relay. If the starter is activating, and the bike won't fire, then follow the same with the sliding coil powering switch. You need to be more specific about what is/isn't happening when you touch what buttons. Really simple circuits to diagnose.

T d F

[Motosan]

Yes, to be more specific. The bike was running two months ago, no issues I could tell. Then two weeks ago I turned key switch and the dash lights would go on intermittently, notably when I toggled the switchgear (it sits a bit loose on the handlebar), which lead me to believe that was the culprit. When the lights were on I would push the starter button and only hear a click. But now the dash lights dont come on anymore, toggling it or not. Does that make sense?

[PeteS]

That switch only turns on/off the ignition. Has nothing to do with indicator lights or the starter circuit. You might just have a bad ground where the battery cable connects to the frame or another poor connection in the wiring harness.

Pete

[Tom]

Check the key switch.  Usually over time the bakelite plastic will melt leaving a light coating on the contacts in the switch.  Scrape clean.  Watch out for the small springs under the contacts.

[Motosan]

Check the key switch.  Usually over time the bakelite plastic will melt leaving a light coating on the contacts in the switch.  Scrape clean.  Watch out for the small springs under the contacts.

Good point. I've never taken one apart. Any advice or resources?

[John A]

Gain access to the bottom of the key switch. Take a silver Sharpie and put a line on the switch body to help when you put it back together. There is probably three screws holding the base on, it is a separate part and holds the contacts that you clean. I used to be able to buy the contact plate with pigtail but lost the part number . You don’t mess with the key portion and you can do it with the switch in place. If you’ve marked it, you don’t have to figure out how the base is clocked by trial and error. Take pictures and it’s easy once you get past the learning curve. Another thing to check is the tail light wireing because it’s on the same circuit as the instrument lights iirc.

[Antietam Classic Cycle]

Good point. I've never taken one apart. Any advice or resources?

This for the larger Loopframe switch, but some of it may apply:
https://www.thisoldtractor.com/moto_guzzi_loopframe_ignition_switch_rebuild.html

[Motosan]

I took apart the switch. Easier than I thought. One of the contacts was a little dirty, nothing crazy. You can see the wire side before I cleaned it, the other side contact is after I cleaned it. I put it back together but unfortunately no changes. No dash lights etc. Side note, if I take the voltage reading on the battery and turn the key, the  first two key positions have no draw but there is draw when it's fully on. Any thoughts on where to look next?

[Antietam Classic Cycle]

Have you cleaned the multi-pin "Molex" connectors? I pull my Convert's apart once a year and squirt them with Caig DeOxit.

[Motosan]

Have you cleaned the multi-pin "Molex" connectors? I pull my Convert's apart once a year and squirt them with Caig DeOxit.

I didn't, they looked clean and I were new when we setup the bike several years ago. I looked around at all the wiring on the bike to see if anything stood out. Everything looks fine at a glance, grounds are in place etc.

Taking a step back. Since I had intermittent power when turning the bike on. When I'd push the start button I would hear the relay click but nothing else and then the power would turn off. Sometimes it would just be power, sometimes not.

Should I take the diode board off to test it? Any other suggestions?

[Antietam Classic Cycle]

I didn't, they looked clean and I were new when we setup the bike several years ago. I looked around at all the wiring on the bike to see if anything stood out. Everything looks fine at a glance, grounds are in place etc.

Taking a step back. Since I had intermittent power when turning the bike on and off should I take the diode board off to test it? Any other suggestions?

I can't see how anything in the charging system would cause your issue.

[Motosan]

I can't see how anything in the charging system would cause your issue.

Is there a safe way to bypass the key switch?