Reg/rec or battery (or something else?)

**Jonathan** · 30th May 2010, 21:55

My charging system is not working and this weekend I did a full inspection and diagnosis. What I found is that the alternator stator seems fine (thank goodness) but that the voltage across the battery does not deviate much more than 1 volt from the battery's own 12v when the engine is revved to 5000rpm. The manual specifies that the voltage should be regulated to between 13.5v and 15.5v at these revs.

So, I checked the resistance between the pins on my regulator rectifier. According to the manual the resistance between the R/W wires and G wires should be between 1-20k ohms. My reading was 16k so this is fine. Between the Y and G and Y and R/W wires the reading should be between 0.5 and 10k ohms. My reading was 11k.

My question is: does this extra 1k ohms resistance suggest that my reg/rec is stuffed or does it just suggest my ancient analogue multimeter (and my ability to read it accurately) cannot be trusted? And, If the reg/rec is fine, can a failed battery result in little to no increase in voltage across the battery when the bike is revved?

I have charged the battery on a couple of occasions since I ran into problems and each time the battery lasts a day or two depending on the speed that I maintain e.g. the more time I spend at 100 km/h or more the longer the battery lasts. Aside from that I have checked all connectors, wires etc. so I believe it has to be either the reg/rec or the battery.

**CookMySock** · 30th May 2010, 22:23

It's either the reg, the stator, or the fuse.

If the stator has good output and it is not shorted to ground, then the reg is suspect. You really need to swap the reg/rect out and try it. This is one of those things a bike shop can do quickly and inexpensively with a spare reg/rect off the shelf.

Steve