[jaketurner]

I gather the purpose of the selenium rectifier is to manage the charge from the generator to the battery. If I'm totally wrong, please scream. My main question is: Can the rectifier go bad in such a way that it shorts?

I still haven't isolated exactly where the short is that's draining my 350's battery. BUT... I know it's not the wire to the starter relay and I know it's not the wire to the ignition. While I haven't confirmed this yet, I'm starting to think that the third wire off the positive terminal goes to/from the rectifier. Right or wrong, that wire contains the source of my short.

So basically I'm asking if the rectifier can fail in a shorted state.

thnx!

Jake

 

[FrankyV]

It is my experience that it can. I found this to be the case on a 1974 Yamaha RD400 that blew the main fuse whenever the ignition was turned on.

 

[Mydlyfkryzis]

The rectifier converts the AC voltage/current to DC. There is usually a separate voltage regulator to control charging. Rectifiers can go bad and short....easy to check with a voltmeter with a diode function. Rectifiers are diodes.

Sent from my SM-T800 using Tapatalk

 

[jaketurner]

excellent! Thanks !!

 

[jaketurner]

Ok, thanks tons! I'm not seeing *any* fuses blowing... which makes me iffy on all this, but it's good to hear that others have had issues with the rectifier. thnx!

 

[jaketurner]

Ok.... crappy update here. I watch videos on replacing 350 rectifiers, and I google the rectifier and I see connectors on the ends... there are no connectors like that on the ancient Rube-Goldberg setup on my 350. Instead, I see four wires: one red that was directly attached to the battery positive post; one green that was directly attached to the battery negative post; and two yellow that go to simple inline-wire-splice connectors. I am not clear on where the two yellow go from there, but my assumption is that they are the AC stator wires (right?).

When I look at wiring diagrams (below) I do indeed see four wires. Red and green are obvious. But the diagram shows a yellow and violet/pink.... and when I watch clips on how to test the diodes there are lots of references to testing across the positive to the two stator, from the negative to the two stator.

I'm asking because I'd like to test this %^$#^ rectifier to see if there is a failed diode that might be causing the short. I've used an ohm meter to see if there's a direct short from the red (nope). One of the voices in my head is saying that I'm chasing the wind here... that there's no reason to mess with the rectifier. But I can't seem to get beyond the knowledge that whenever I attach the rectifier's red to the battery, it results in an instant drain on the battery.

So do I use my DVM (on diode) to test across from the red to each yellow? and then green to each yellow?

thnx....

 

[jaketurner]

View attachment 198849

 

[JAYinNY]

It has been my experience that the ancient OEM rectifiers can test good but still cause a current draw. Just replace with a modern one.

 

[Oldgeezer]

Ok.... crappy update here. I watch videos on replacing 350 rectifiers, and I google the rectifier and I see connectors on the ends... there are no connectors like that on the ancient Rube-Goldberg setup on my 350. Instead, I see four wires: one red that was directly attached to the battery positive post; one green that was directly attached to the battery negative post; and two yellow that go to simple inline-wire-splice connectors. I am not clear on where the two yellow go from there, but my assumption is that they are the AC stator wires (right?).

When I look at wiring diagrams (below) I do indeed see four wires. Red and green are obvious. But the diagram shows a yellow and violet/pink.... and when I watch clips on how to test the diodes there are lots of references to testing across the positive to the two stator, from the negative to the two stator.

I'm asking because I'd like to test this %^$#^ rectifier to see if there is a failed diode that might be causing the short. I've used an ohm meter to see if there's a direct short from the red (nope). One of the voices in my head is saying that I'm chasing the wind here... that there's no reason to mess with the rectifier. But I can't seem to get beyond the knowledge that whenever I attach the rectifier's red to the battery, it results in an instant drain on the battery.

So do I use my DVM (on diode) to test across from the red to each yellow? and then green to each yellow?

thnx....

Yes, yellow are from alternator.

 

[jaketurner]

Jeezzz.... Well, I've done the diode testing and concluded that the existing R/R doesn't outright fail. But a local old honda mechanic today told me that they can test ok on a digital meter and still "bleed" voltage... and when I told him that it took right about 2.5 to 3 weeks he said that would be about right.

To be on the OCD side, I did check that both yellow from the stator have some level of continuity with one another, but that neither has *any* short to ground. This is good news. So today I've been digging around for an affordable R/R replacement. They seem to run anywhere from $65 to $119 for a 1970 350. A good friend (excellent mechanic) says, "You can buy a full wave bridge from an electronics store dirt cheap and just wire it in. Something with a 100v+ PIV rating and 25+ amps would be fine."

Anyone else tried that? If so, where did you get the FWB from?

thanks!

Jake

 

[crazypj]

Selenium rectifiers were thebest available for the price when bike was built, you can get more efficient rectifier with built in regulator from a modern Honda. Wiring will still be te same although the yellow wires to AC generator may now be black (cost cutting)
Unless your going 10/10 restoration, I would take efficiency over originality

 

[jaketurner]

Thanks everyone for the advice and input. I got a new combo-rectifier-regulator, replaced it, and no longer have the short. In addition, when rev'ing RPM I can now see the charging of the battery of between 13.6 and 14.4v.

all happy now...