Rostra rear brake ground question

[lvldcook]

My Rostra suddenly won’t stay engaged after several years and several rainstorms. WIth the bike off, when I measure resistance to ground of the rear brake sense that goes to the Rostra unit connected to connection 30 of my brake light relay, it measures a fraction of one ohm. When I turn bike power on (not starting bike), the resistance increases to about 19 ohms. Is that normal?

 

[B.D.F.]

According to Rostra, all signals sensed have to be below three Ohms to be considered 'low' state. 19 Ohms is definitely too much.

Brian

My Rostra suddenly won’t stay engaged after several years and several rainstorms. WIth the bike off, when I measure resistance to ground of the rear brake sense that goes to the Rostra unit connected to connection 30 of my brake light relay, it measures a fraction of one ohm. When I turn bike power on (not starting bike), the resistance increases to about 19 ohms. Is that normal?

 

[MAN OF BLUES]

ok, now I have to ask, as you have to posts going, and 2 problems.. all "just popped up" simultaniously.. very interesting..

http://forum.cog-online.org/concours-14-zg1400-general-chat-and-tech/gear-indicator-stuck-in-neutral/msg672094/#msg672094

also, you posted this in the C10 section... needs to be moved, along removing the second post here on the C10 section, which is a duplicate..

 

[lvldcook]

Thanks. Didn’t realize that

 

[lvldcook]

Thanks Brian. Any thoughts on how to track down the 19 ohms? I’ve replaced all the accessory relays already. I appreciate your electrical knowledge in this forum.

Another non-electrical engineer/technician question: Is it even valid to try and take a ground resistance measurement with a handheld meter with the bike power? Maybe I’m fooling myself about the 19 ohms.

 

[lvldcook]

(Reposting in C14 section)

My Rostra suddenly won’t stay engaged after several years and several rainstorms. WIth the bike off, when I measure resistance to ground of the rear brake sense that goes to the Rostra unit connected to connection 30 of my brake light relay, it measures a fraction of one ohm. When I turn bike power on (not starting bike), the resistance increases to about 19 ohms. Is that normal?

 

[rwulf]

No, the Rostra wants to see 4 ohms to ground (I believe)
If the resistance is slowly rising that suggest you might have
some kind of bug living in the path or a stray voltage getting
in there. Why thing like this happen after working for years
is the real question we are all looking for the answer to.

 

[rwulf]

I will try and answer this, No. Unless you have some fancy expensive
equipment it's not a valid way to measure resistance.

 

[B.D.F.]

I think in this case that yes, multimeter Ohm readings are valid. Not perfect but we do not need perfect and 19 Ohms is clearly well outside of 3 Ohms.

As Rich pointed out, it is important to note that this is a C-14 installation, not a C-10. I did not even realize that until Rich mentioned it and thought we were talking about a C-10.

You can track the resistance (Ohm) back through the circuit but I would just kinda' skip ahead and check where the brake light relay (because you have a C-14, I know you must have that relay) connects to ground and start there. It is IMO the most likely place you are getting this resistance. If the ground is attached to anything that is attached to the swingarm, that alone is a bad situation. Because the Rostra draws so little current, I always suggest connecting ALL the ground connections together and then make a single connection to the ground wire (black w/ yellow stripe) in the user available contact wires provided, either in the rear of the bike or the front, under the top / left fairing cover. If you are already using one of these grounding connections, they check the barrel connector to make sure it has not corroded; it it has corroded, mechanically clean it until it is bare metal on both connections, then swipe the male in grease (yep, a joke in there somewhere) and reassemble. The grease will prevent further oxidation.

The other place to check is the ground connection between the harness and the bike. This is located right behind the battery cover and consists of two 8mm cap screws that thread directly into the frame; one is the ground from the battery, the other is the main ground point (called 'star grounding'). Remove both, clean them until clean metal is the only thing left (I like a rotary wire brush in a drill or similar), coat the entire wire eye and bolt with grease and reassemble. Also of course clean the frame under the wire connection before reassembling.

Usually things like this a very much single point issues, especially since the problem developed rather than occured at installation. So it is almost certain that you have one point that is corroded, loose, or the connector has become loose from the cable (crimp failure) or the end of the wire is broken where it attaches to the wire end (the ring connection or the bullet connector).

Best of luck and you should be able to find it reasonably easily.

Brian

 

[lvldcook]

Thanks Brian. Appreciate your time on this. I’ll continue to trace this out. One issue I have is not knowing where all the “joint connectors” that connect together three or more grounds are located all over the bike. My schematic shows at least seven of these that assemble grounds.

 

[B.D.F.]

True enough but Kawasaki's ground junctions are waterproof, weatherproof and extremely well done. It is highly unlikely that there is a problem with the original OEM ground junctions IMO. They are very well sealed and have never caused a problem that I am aware of in the past.

Again, trace your own ground from the Rostra to the 'ground' on the bike, wherever it is. I believe you will find your problem somewhere in that series of connections.

Brian

Thanks Brian. Appreciate your time on this. I’ll continue to trace this out. One issue I have is not knowing where all the “joint connectors” that connect together three or more grounds are located all over the bike. My schematic shows at least seven of these that assemble grounds.