Topic: Electrical leak. CB350F - Rectifier related?

[KiwiShaz]

Hey guys.

My CB350F battery drains real quick if the keys left on. I can watch the voltage plummet with a multimeter, about 0.1V every few seconds. It doesn't drain with the ignition off not even over days. I know that means it's not usually the rectifier but hear me out. The battery is near new and holds it's charge when completely disconnected just fine.

I've tested the rectifier with the diode setting on my multimeter and the results indicate it's functioning properly.

With the rectifier plugged in and the key off there is no loss of voltage across the battery terminals. Turn the key the voltage starts to drop fast and it stops doing so the second I unearth the rectifier from the bike. The rectifier is the standard one all the fours seem to have. Can someone confirm for me that the flat folded metal tab coming of from the green wire is an earth?

I have a spare three phase rectifier off a honda atv to swap it with and while doing that I noticed that the green wire into the harness is quite badly melted.

The three yellow wires shouldn't have any voltage or current if the engine isn't running correct? So my leak is highly likely from red wire through a dodgy diode to green wire (two dogy diodes, surely not)? But why only with the ignition on? It's totally independant of the ignition switch. And why does the multimeter show the diodes are all ok?

My mind tells me the rectifier is not causing my drain... only I can see with the multimeter that it appears to be. It only drains when the metal tab that comes out of the green wire is earthed - and only when the ignition switch is on.

I don't wanna fully hook up the new rectifier if i'm going to cook it.

[Mantree]

More likely the regulator than rectifier but check for shorts first

Sent from my ME302KL using Tapatalk

[tlbranth]

http://www.electrosport.com/technical-resources/diagnosis-center

[Bodi]

The rectifier is connected to the battery all the time, it has nothing to do with the key switch.
There's a healthy discharge as soon as you turn the key on, but removing the rectifier ground should not make any difference... that's the odd thing about what you report. No power should be passing through the rectifier except when the engine is running. Check your main ground wire - a large wire from battery "-" to an engine mounting bolt. If the entire bike is grounding through the rectifier small wire, I would expect that to melt when the starter motor is used. You must have a very good connection direct from battery "-" to the frame and engine case.
The alternator field coil and ignition take a lot of current whenever the key is on, through the MAIN fuse. You can remove the HEAD and TAIL fuses and reduce load but the field coil and ignition will always be on unless you detach the black wire from the regulator and put the kill switch to OFF (STOP?).
Try removing the HEAD and TAIL fuses and that black wire. If you switch the kill switch to OFF the remaining load should be very light: maybe an indicator light or similar? I can't check the wiring diagram to say for sure right now.
The very early 350-Four bikes only had one fuse, I believe. Could be wrong - but if that's your bike then switching kill to OFF and removing the black wire from the regulator would leave only the lighting load.

[KiwiShaz]

Sorted it out. All the green terminals were switched positive. Went around unplugging them all and eventually found that the green regulator terminal is supplying 12V.

I didn't realise till now but the whole green/earth part of the loom was only earthed to the frame at the rectifier hence why I initially thought that the culprit. I've since reinstated the second green frame earth.

So time for a new regulator? Recommendations? I'm not against going to a regulator/rectifier combo. Tomorrow I will try to work out if the reason the regulator is shorting can be fixed.

[Bodi]

The regulator is not very complicated. Not much there to fail.
How did you find that it puts +12 on its green wire? This may be normal... disconnect the green ground wire from any switched on bike load - a lamp for example - and it will measure +12V.
The alternator field coil (white wire on regulator) will draw around 3A when the keyswitch is ON. (you can count on the regulator being full ON when the engine is not running)
Each (original) ignition coil will draw a bit over 2A, the points turn them on and off but I think one is always on and both are sometimes on. Some aftermarket electronic ignition modules will have both on almost all the time.
So: assume minimum 5 amps constant battery draw with all lights off. Lighting adds more depending on what lamps you use.
That will drop a fully charged battery down from float voltage quite quickly. Lead-acid batteries have a discharge curve that drops fast to around 12V where it drops much slower as the battery discharges then drops faster again as the charge runs out. On charge the voltage rises slowly as the chemistry recharges, then faster when fully charged, at float voltage a fully charged battery will draw almost no current: putting power into a fully charged battery just turns its water into hydrogen and oxygen through electrolysis.

[KiwiShaz]

If I remove only the green wire from the regulator and measure the voltage between the terminal and the batt neg (or any earth) it reads 12.3V.

Damn I thought this was definitely abnormal? Excuse my ignorance but won't that mean most components are getting switched hot from black and also from green? Something failed while I was syncing my carbs on Sunday. All my electrics were working fine, battery wasn't draining. By the time i'd finished syncing, which was only five minutes of running, the battery was dead and none of my components have worked since either. Presumably because they have two doses of switched hot and no neg?

Thoughts?

[tlbranth]

Follow this chart. It ain't hard.
http://www.electrosport.com/media/pdf/fault-finding-diagram.pdf