Verification good/bad earth.

[Roy_W]

I have been trying for a while to repair my TripMaster, OK no luck there, and I noticed something unusual whilst testing various components on the bike.

For example I have an automatic chain oiler which requires a 12v+ feed. The feed/return have been taken directly from the battery with an inline fuse. When I test the voltage running back to the battery it registers roughly 12v.
But when I take the return lead and and earth it to the frame it only registers 7V.

Is this an indication of a bad earth somewhere else on the bike, if so, how do I go about finding the faulty component.

Cheers Roy

[BobA]

Roy

Not sure about this one. If both the + and - of the chain oiler are connected directly to the battery, I cannot understand how you would get a bad earth to it.

If however what you are saying is that by testing between the feed, or return to the chain oiler (with the + probe) and then grounding the - probe to the frame you are getting a voltage drop, it would indeed sound to me like a bad earth.

Do the same test but introduce a new direct earth wired from the - on the battery to the frame/engine or wherever you are grounding your probe.

Good Luck

Bob

[Roy_W]

Roy


If however what you are saying is that by testing between the feed, or return to the chain oiler (with the + probe) and then grounding the - probe to the frame you are getting a voltage drop, it would indeed sound to me like a bad earth.

Bob

Yes this is the test that is worrying me, I also have the same drop on other eletricals elemants. How do I go about finding which element is creating the bad earth. Is it simply a case of disconnecting one element at a time until I find the fault or is their an easier method.

Roy

[throll]

Roy


If however what you are saying is that by testing between the feed, or return to the chain oiler (with the + probe) and then grounding the - probe to the frame you are getting a voltage drop, it would indeed sound to me like a bad earth.

Bob

Yes this is the test that is worrying me, I also have the same drop on other eletricals elemants. How do I go about finding which element is creating the bad earth. Is it simply a case of disconnecting one element at a time until I find the fault or is their an easier method.

Roy

It could be another problem too. Something is pulling your voltage down try to disconnect parts which are on 12V one by one.... and measure voltage.... but I asume, that will be earth problem...

[BobA]

Roy

Often a bad earth manifests itself through silly faults on other items.

Ever followed a car that puts his brakes or indicators on, and all the other lights come on dimly??? That's down to a bad earth!
Basically, what happens is if the earth for all those components is not linked to the ground (frame or chassis) properly, the component that is trying to work (e.g a brake light) tries to find it's earth, it cannot, so what it does is returns back through all the other components (earthed to the same point) until the resistance is high enough to seem like an earth (which is why in my example all the other lights come on dimly)

Get the Haynes wiring diagram, which shows which items are earthed together, then isolate components by either disconnecting them or removing a fuse.

Work in a logical order, and by a process of elimination it will eventually become clear.


Best of Luck


Bob

[Roy_W]

I found my problem . there was a badly soldered feed coming into the "Automatic Oiler". Everything looked OK but a test with a multimeter showed that the connection was a little sporadic.

Solution, unsoldered the wire, cut it , resoldered and everything is hunky dory again.

Now if I could only find the bloody problem with the TripMaster. The electonique problem are frustrating to say the least.