Big Red Speedo Light question

[MFW]

Bought a new bike that had a speedo on it. The light only works when i touch the edge of the case when putting it inside the head unit. Once it pops into place with the rubber grommet the light goes out. Seems like a ground issue but I went through and checked all the wires in the harness. Is there something inside the head unit that will ground the light? Any help would be great! Thanks

Matt

[MFW]

Any Hondaline Speedometer experts out there?

[El Camexican]

Any Speedo experts out there?

David Hasselhoff comes to mind.

[MFW]

Haha, good one!

[ps2fixer]

Far from an expert on these, but I've made reproductions from NOS sockets for these. The light housing shouldn't effect the light in any way, the wires goes directly to the socket/bulb. There should be a green wire + brown wire. Green is the ground, brown is the +12v and should only give power to the bulb when the light switch is turned on. Maybe the socket is corroded, or the bulb is failing?

Here's some photos to reference on my reproduction socket, it should look very similar to what you have.

https://www.ebay.com/itm/192928084416

[MFW]

Thanks Ps2fixer, I will take a look at the wires again. I took out the harness and cleaned all the connections. I even switched the bul because I thought it was bad. Do you still sell the harness?

Matt

[ps2fixer]

I do still make the harnesses (full OEM replacement style), just have a bit of a back order built up. Been trying to keep up with ebay stock, so haven't been able to dedicate much time to making harnesses. Harnesses just eat up a lot of time to make them.

[Jd110]

Are the rubber mounting grommets in place, under the head unit? Head unit shouldn’t be grounded(front-end is through neck bearings), but you can check with a multi-meter. You can also check continuity between the socket base and the end of green wire on the socket pigtail. If the light comes on when it touches the side of the head unit, tells me the head unit is grounded AND you lost the ground connection to socket.

[MFW]

The rubber grommets are in place. I will go through and clean and reconnect everything again. Thanks

Matt

[Jd110]

I just double checked mine.....I was wrong about the head unit not grounded. I’m getting ground through the speedo cable, now. Maybe, pull back the rubber boot from the socket. Just be careful not to rip it(grease wires so boot can slide a bit). You will see where the green wire is connected to back of socket and try cleaning it. Never tried to soldier that...but I would. Once you find the problem, you could then decide on buying new parts.

[ps2fixer]

The grounding of the speedometer housing shouldn't matter as the bulbs don't ground through the case, the socket is rubber mounted so the green wire (ground) runs directly to the bulb. It just sounds like a bad connection in the socket, or if the movement is more like a tap, could be a blown bulb and the filament is welding to the probe inside the bulb and lights up, and once turned off the extreme temp change breaks the weld and it drops back down and is free hanging (depends on bulb design/type internally). Ever had a headlight or tail light you could smack and it would come back on? That's what's happening in those cases.

FYI, you can remove the socket from the speedometer and the bulb will work still. You could check the socket connections out as well as the bulb and diag a bit more where you can see what's happening. Could try to wiggle the bulb to see if it's a socket connection problem, or lightly tap it to see if it's the bulb being blown just right where it cam light back up. If neither is bad, then I'd start digging down to where it connects to the harness and such.

Also the wiring probably is really old, so it's possible the insulation on the wire is brittle and broke inside the socket. Pushing the wire "in" on the socket and having it light up might be a sign of a bad wire, same story if you lightly pull on the wire and it doesn't work.

[Jd110]

Cory, here is a picture of where ground wire connects to the base of the socket.
You can see I’ve got the ground wire disconnected in headlight bucket and touching the speedo it all works. So, if it works when touching the side of head unit...bad ground connection.

[ps2fixer]

I see, with it normally installed is it possible to get the socket housing to hit the speedometer housing? I thought the rubber mount made it near impossible for the two to come in contact unless you remove/damage the rubber grommet. The NOS sockets I found are the same design though, didn't know the rubber pealed back so easily.

[Jd110]

Yes, op describes it pretty well in first post. Possible it’s fixable. If not, good chance he can find a new one. Win-win

[MFW]

I disconnected the wire harness to the speedometer and wired it directly to the main harness. Same out come. I even changed the bulb with a new one. Same outcome. I will keep digging and keep cleaning connections. Something has to give.... right? Haha