Elecrical gremlins

[MikeyG]

I have had a problem with my gn250 running rough for a while. It will idle ok but when i turn the headlight on the idle speed drops by about 1000 rpm. I tracked it down to the regulator/rectifier and replaced that about 2 months ago. Now the problem has started again so i checked the new regulator and it has blown as well. Did i get a bad unit or is there likely to be something else causing the reg/rec to die? What else should i be checking?

I have checked the alternator output, no-load voltage and insulation. Battery was new under a year ago. A led taillight bulb is the only electrical modification.

 

[MikeyG]

Bump. Anyone got ideas?

 

[Rich Ard]

Could be your stator or the wiring leading to the R/R. I'd suspect your stator rotor is toast. To the multimeter!

 

[Sonreir]

What test did you use to determine that the regulator has failed?

 

[MikeyG]

At work right now. I'll post scans of the pages from the manual tonight.

The more i think of it, the more i think my multimeter is bust. According to the multimeter there is 1.25 million ohms across the reg/rec where there should be only 7-8 so i would think the battery shouldn't get a charge but the voltage across the battery terminals is higher with the bike running an increases with rpm.

 

[MikeyG]

Just realised my meter might not be overcomming the breakdown voltage of the diodes. I will redo all the tests tonight with a different meter and post both the methodology and results.

 

[MikeyG]

Hi guys. sorry for the slow reply, life got in the way for a while.

I've attached the pages from the manual showing the tests I did. I'm still not getting the correct numbers for the reg/rec test. I'm getting 145000ohms where it should be 6-8 and 32000 where it should be 65-85. It still seems to be charging though so I'm giving the reg/rec another chance. At $250 for a new reg/rec I don't want to go ahead and change this one too soon. I might try and build my own from separate reg/rec units from an auto electronis store.

After checking all the cponnections I decided the earth connection to the reg/rec was dodgy. The stock location has it connected to the feame with one of the battery box mounting bolts. This bolt has a rubber bush and paint on it though so I'm not sure how good it is. I've moved the earth to the bolt on the engine that the negative lead from the battery connects to, proper metal to metal connection this time. It was running properly in my driveway after doing this I'll give it a week of commuting and see how it goes.