V-Strom Power Generation Checks
This write-up is for the DC power generation system of the DL-650A, model years 2012-2016 (at least), having a 400W magneto followed by a shunt regulator. With adaptation of power and voltage levels, it can be applied to earlier DL-650 and DL-1000 bikes having a magneto and shunt regulator.
A Precaution Re DC Generator:
There is a pitfall in replacing only the rectifier/regulator or only the magneto stator if either has been damaged by the other. The rectifier diodes are individually under stress approaching what could damage them, and a short in the wrong place on the stator can result in much higher than normal current going through the diodes furthest (electrically) from the short, possibly damaging them. It is also possible that failure of one or more rectifier diodes would cause excessive stator current, damaging it. For this reason, I recommend (as does the service manual) verifying the operation of both the rectifier/regulator and the magneto when either has been implicated or replaced. These checks can be done as follows.
The magneto can be checked by first unplugging it from the regulator (at the 3-wire mated connector pair near the regulator), then measuring AC voltage between each pair among the 3 pins (on the magneto side, of course.) At 5000 RPM, each pair should measure a bit over 60 V RMS and the readings should be within a percent of each other among the pairs. A mismatch indicates shorted turns. Uniformly low voltage indicates magnet problems (or lots of shorted turns uniformly distributed among phases, which is unlikely.) Using the resistance function on a DMM from any of the 3 wires to ground (with the stator installed on the bike) should show many MegOhms. (open) The resistance across each of the 3 pairs should be no more 0.3 Ohms higher than what your meter reads with its leads pressed together hard. Those readings should be uniform for the same contact pressure between probes and pins. (Probe lead resistance and probe contact resistance tend to swamp the winding resistance being measured, so interpret readings accordingly.)
The stock shunt regulator/rectifier can be checked for its bridge rectifier being intact as follows: Unplug both cables from the regulator. Using the diode function on your DMM [a], measure from each of the 3 pins on the 3-wire regulator input (the black wires), using the red DMM lead, to the black/red regulator output wires on the 4-wire regulator output, using the black DMM lead. All 3 readings should read as diodes. Then, using the diode function again, measure from each of the 3 pins on the 3-wire regulator input (the black wires), using the black DMM lead, to the black/white regulator output wires on the 4-wire regulator output, using the red DMM lead. All 3 readings should read as diodes. If all 6 diode tests showed a good diode reading, the rectifier part of the regulator is working.
[a. If your DMM has no diode function, measure the "resistance" of a diode using the resistance (or "Ohms" or "KOhms") function, with the red DMM lead on the anode (non-banded end) and the black DMM lead on the cathode (banded end), and note the reading. Treat readings within 25 percent of that as indicating good diodes when probed the same way. (Of course, you have to start with a good diode for this work-around to work. A new 1N4001
diode from RadioShack will do.) ]
Regulator Shunt Check:
Checking the regulator/rectifier regulation function is harder. Start by unplugging and reconnecting its 4-wire connector a few times to reduce contact resistance (which can throw off the following diagnostics, or even cause the appearance of a weak charging system.)
For what appears to be a weak charging system, temporarily remove the headlight connectors and turn off any customized loads. If this allows the battery voltage to begin rising, with the engine running at idle speed (about 1300 RPM), the shunt regulator is not malfunctioning short.
Charge Done Level Regulator Check:
If battery voltage (as measured at the battery terminals) exceeds 14.8 VDC at any time when the charging system is running, the regulator is bad. It should be immediately replaced (or the bike parked or the regulator output unplugged) as this fault will damage the battery and could create a hazard.
If the battery voltage does not reach 13.6 VDC after the post-start recharge has had a chance to complete [b], either the magneto is failing to supply enough current to power bike loads and charge the battery, or the regulator is reducing controlled power flow at an incorrect voltage level. (This is why the magneto check should be done too; these cases are hard to distinguish otherwise.) If the magneto diagnostic absolves the magneto, regulator output contact resistance is normal, and there are not excessive (custom) electrical loads on the bike, and the end-of-charge battery voltage is too low, then the regulator "charge done level" is faulty and the regulator needs replacement.
[b. After a normal start, 10-15 minutes of normal riding should allow the charging system to replenish the energy taken from the battery during the start. After a difficult start, with lots of cranking, recharge can take much longer. That implies a problem outside of the power generation subsystem. ]