It looks as if I’ve got another rotor fail on me. No resistance across slip rings. Checking my invoices I replaced this less than a year and a half ago. Am I just unlucky or could there be a reason it’s failed so early?
Alternator rotor.
- Thread starter scooter paul
- Start date
Beemerboff
Registered user
Most windings fail in the last couple of inches , where they go under the slip rings then are soldered to the slip rings.
So a quick look at the solder dots on the end of the slip rings, than a more careful check on the windings, if you can locate the wires coming out from below the slip ring and carefully cut through the lacquer covering with a box cutter blade you will be able to check the remainder of the wiring for continuity.
If the remainder of the windings are OK some rewinders will press off the slip rings, unwind a couple of turns , refit the slip ings and resolder the wires for much less than the cost of a full rewind, maybe you have nothing to loose by trying it yourself.
FWIW some of the suppliers aftermarket crank mounted ignitions suggest that you clean off any solder blobs so that the new sender sits flat on the end of the rotor, and this can exacerbate the problem somewhat -DAHIK!!!
So a quick look at the solder dots on the end of the slip rings, than a more careful check on the windings, if you can locate the wires coming out from below the slip ring and carefully cut through the lacquer covering with a box cutter blade you will be able to check the remainder of the wiring for continuity.
If the remainder of the windings are OK some rewinders will press off the slip rings, unwind a couple of turns , refit the slip ings and resolder the wires for much less than the cost of a full rewind, maybe you have nothing to loose by trying it yourself.
FWIW some of the suppliers aftermarket crank mounted ignitions suggest that you clean off any solder blobs so that the new sender sits flat on the end of the rotor, and this can exacerbate the problem somewhat -DAHIK!!!
Thanks. I’ll have a play. As you say nothing to lose as I’ve already ordered a new one. Still curious as to why it’s failed so early. Where the wire is soldered to the ‘front’ slip ring did look a bit rough. I’ll check more deeply.
This morning I’ve done some more tests on my failed rotor. Across the slip rings, instead of getting 3.4 or thereabouts resistance, I’m getting direct continuity. I now suspect, for some reason, there’s a short between the rings as opposed to what I’ve seen before on others, a break in the windings. Anyone else seen this?
Most multimeter’s would be challenged to give an accurate resitance measurement below about 100 ohms. If you’ve used your meter before and achieved accurate results then ignore my theories 
Tried another multimeter and rotor is ok. So now looking at wether the Electrex regulator rectifier May be faulty.
B Murr
Registered user
Do you still have the one you replaced a year and a half ago, maybe multimeter wrong on that too?
The one I replaced a year and a half ago was faulty because a new rotor cured the non charging issue! The bikes been fine since, until recently when it stopped charging again. I suspected a failed rotor again but it appears not to be the case.
Big Jets
Registered user
Think when my rotor failed I had no warning lights on the dash are you showing any signs of life on the idiot lights
I have a custom loom and instruments using motogaget components. The charging circuit is separate from the lights etc so easy enough to check individual components. So to answer your question, no idiot lights except oil pressure and neutral light. No charging light.
I spent some time attempting to isolate the non charging issue. All the tests recommended by Electrex were done and nothing amiss found. They do say these tests are indications and not necessarily conclusive. Still not charging. From online research it appears as if these Electrex regulator rectifiers are not without their faults and an improved version was produced at some time. I’m tempted to bite the bullet and order another but a phone call will be made to the manufacturer this week to discuss. Anyone else had an issue with an Electrex RR45?
By a process of elimination and using known, good, components it has been identified as a faulty Electrex RR. New one fitted and now charging at 14+ volts.
Beemerboff
Registered user
Good technique this elimination and replacement.
Just had a problem with my R75 starter, pushing the starter button usually had the desired effect, but sometimes a click then nothing.
So I dug into my stash, replaced the RH switch, wiring to the relay, relay, battery and starter, and was able to isolated the problem as a loose connection on the battery / starter lead!
To be fair I have a Motobatt battery which has a universal little angle bracket which bolts to the battery, and then the cable is bolted to the bracket, and I had only checked the visible bolt at the battery and missed the bolt at the lead which was hidden up behind the side cover.
So I replaced the leads with new HD ones which I was happier bending and twisting to fit without the intermediate bracket.
At the same time as I refitted the 3 pin plug on the back of the diode board which was dislodged when I was replacing the starter.
FWIW a stock 20 AH Motobatt fits into the big 30 AH battery tray OK and spins a 1000 cc motor over fine, and the slim BMW G/S specific Motobatt also fits(just) and works, but has to be packed well forward to avoid the leads shorting on the frame DAHIK!
We have had 60mm of rain in the couple of days since it was all bolted up so haven't had a chance to give it a read test, hope that is the end of it for the season!
Just had a problem with my R75 starter, pushing the starter button usually had the desired effect, but sometimes a click then nothing.
So I dug into my stash, replaced the RH switch, wiring to the relay, relay, battery and starter, and was able to isolated the problem as a loose connection on the battery / starter lead!
To be fair I have a Motobatt battery which has a universal little angle bracket which bolts to the battery, and then the cable is bolted to the bracket, and I had only checked the visible bolt at the battery and missed the bolt at the lead which was hidden up behind the side cover.
So I replaced the leads with new HD ones which I was happier bending and twisting to fit without the intermediate bracket.
At the same time as I refitted the 3 pin plug on the back of the diode board which was dislodged when I was replacing the starter.
FWIW a stock 20 AH Motobatt fits into the big 30 AH battery tray OK and spins a 1000 cc motor over fine, and the slim BMW G/S specific Motobatt also fits(just) and works, but has to be packed well forward to avoid the leads shorting on the frame DAHIK!
We have had 60mm of rain in the couple of days since it was all bolted up so haven't had a chance to give it a read test, hope that is the end of it for the season!
Beemerboff
Registered user
oops!
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