Neil Robinson said:You don't even need a multimeter, just two lengths of wire, one connected to each rail or controller output connection.
Support the loco upside down and touch one wire to one wheel and the other to a wheel on the opposite side. The motor should run. Keep one wire touching one wheel and move the other to each of the wheels on the other side in turn. Then move the first wire to each of the wheels on its side in turn. This should reveal any wheels that aren't picking up properly.
Many have written about what appears to now be a power to the rail issue. The first bit of the blade relies on power from a piece of metal on the blade moving sleeper. This can get tarnished. The next piece relies on a pressed or screwed in piece of metal that is from the stock rail, this can become dislodges ir the screw comes loose. The first part can also get power from the fishplate but that can be tarnished. I modify all my points by putting in a jumper wire to replace all the potential loss of power. Yes I know it is a pain but outside years of weather do take a toll on these parts and power transfer.So, it continues to disappoint. I am getting to the point where I will probably sell it, no other loco I have is so temperamental on the track. Specifically today, in perfect running conditions (sunny, and dry for 2 weeks). It keeps on getting stuck on one point. But only when the point is set to straight. I've cleaned the point rails several times now and no other loco has a problem there. Similarly I've cleaned, as always, the backs of the wheels. It's also worth mentioning that it's been on the workbench of a modeller who knows his stuff, and he could not find anything wrong (I don't know him well though and he wasn't running stuff that day so I felt it inappropriate to ask him to run it on his track).
Below should be a short video where you can see exactly where on the point it stops. No other loco from Stainz to Sachsen Meyer or V251 diesels has a problem there. And ironically the Rugen is one of few I bought new. Given that others rave about their reliability, I do suspect I got a dud.
Does anybody have any thoughts on why it happens?
Not sounding my own horn, but what I said back in post #31 will absolutely show which wheel is not picking up power.... then you can determine why... that loco should all wheel pickup according to an earlier posts, but that has not been proven to me yet. Does it indeed have pickup brushes on all 8 wheels?
If the OP cannot verify, can someone post the link to the exploded parts diagram?
Could be wheel pickup, bad brush, wheels lifting on a warped switch, bad power to the moving blade, etc. If you use a deterministic method to figure this out you can get the answer. With all the possibilities (only some of which I have listed), you can flail around with speculation forever.
Since this has been going on since May, may I gently suggest that the "flailing around / speculation" approach has failed thus far?
Yes !!!! 6 years of frustration, but I'd guess this problem has been ignored for 6 years, or it has been sitting on a shelf 6 years.May 2014!