Tested Rectifier ???

[CAZCO]

Hello, just tested my Rectifier and Ohm meter showed no reading. Manual said it should read .36 - .48 Ohms.....Checked leads on different contacts and still no reading. Where is the best place to buy Shindengen SH545-12 Rectifier or what is the best way to upgrade this system.

Thanks

Gary C

Arkansas

[KenP]

When I had my First Gen, I used this guy for my R/R and connectors:

 

http://www.easternbeaver.com/index.html

[MiCarl]

In the rectifier test you are testing diodes. Most meters won't read them correctly on just any range, they need to be set to the range that supports diode testing.

 

The meter I usually use needs to be set at the 1K ohm range to correctly check rectifiers. All the other ranges read them open.

 

It's unlikely all 6 diodes in your rectifier failed. Check the manual for your meter.

[frankd]

The readings given in the manual were with the genuine Yamaha electrical tester, which was an analog (actual physical meter to read results). Most analog meters have full battery voltage (1.5 volt DC, on Rx1) across the leads when ohmeter is selected. Most diodes have about a .6 volt drop across them when they are conducting, so if you connect the leads from an analog meter across a diode in the forward direction, the meter will read approximately 2/3 scale. In the reverse direction, it shouldn't move.

 

With a digital meter, as Micarl mentioned, the ohmeter leads only have a very slight voltage across them, and it is way too small to allow the diode to conduct. However, in the special range marked with a diode symbol, the leads do have enough voltage to test a diode. When the diode conducts, the meter will usually indicate .6-.75, and in the reverse direction, it will usually indicate over range ( or 1.----) on a good diode.

 

I gather you are working on a charging problem on your 89. Regulator/rectifiers don't go bad very often. I did have one on my 83 that had 1 diode go bad. The other 5 were still fine. When you tested your stator, did you test the white leads to ground? When you check from any of the white stator leads to ground you should read infinity (open circuit). If your stator is NOT grounded and passes all the other tests in the manual AND all 6 diodes in your regulator test good (BTW, MiCarl was also correct when he said that all 6 diodes likely weren't bad), there is another stator test you can do. Connect a 75W incandescent lamp across each pair of white wires (3 lamps). Then start the bike and bring it up and watch the lights---all 3 should be equally bright. At idle they will merely glow, but at 3K RPM they get pretty bright. The last stator I had to change had an intermittent shorted coil. It read open to ground, and when you first started the bike, all 3 were equally bright. But after about a minute, one went very dim, and another went slightly dimmer.

 

The attached picture shows how bright a good stator will light a lamp. I only used 1 lamp to do the test, but it'd be easier for you to use 3 lamps. Do this test with the stator unplugged from the regulator.

Edited June 3, 2013 by frankd

[CAZCO]

Hey Guys!

Thanks

My problem is when I rode my bike to town, on way back the volt meter went from normal reading of 14-15 down into the yellow, when it hit yellow I couldn't rev it enough to keep running and died. First time I jumped it and got it to my son's house. A few days later, it started and I headed to shop, on way to shop it started building back up on volt meter. So I came home.

I am truck driver so when I got back home in about a week, I took her to town again.

This time same, way in, ran great, way home didn't make it. Won't jump, so called wrecker.

 

Tested Rectifier with my meter on 200, 2k, 20 k, NO reading.

After reading your posts, I tested to battery ground, still no reading from rectifier.

Tested stator at same plug, on same readings, to ground, all three prongs read .99 - 100.

When I did an Ohm test not to ground but to just the three prongs themselves, on 200 I got .12, .23 .34. Just by only testing ohms thru the rectifier itself.

 

Will start bike and see what volt meter reads now, just for the fun of it.

Thanks

[CAZCO]

When I turned on the key, volt was about 12. When started, longer it ran, started moving down slowly. Proably because I wasn't driving at highway speed,so it didn't need as much spark just at idle.

 

Any suggestions are appreciated!!!

Gary C

[frankd]

The three white stator leads should read identically to each other. The spec. is .42 ohm @ 68 degrees, plus or minus 15%. Are you using a digital meter? If so, you need to compensate for the meter lead resistance. Put you meter on the lowest range (200 ohm?) and touch the meter leads together and read the meter. You will probably read .1-.2 ohm. If your stator windings are reading perfectly correct, you will read .42 ohm plus .1 ohm (meter lead resistance) which equals .52 ohm. All three phases of yours read lower, indicating that you have a shorted stator. Also, you should read infinity to ground from the white wires. If I understood your readings correctly, your stator is bad.

 

Frank

[CAZCO]

Hey Guys,

Local shop said when you get any reading on the stator at the plug on any of the three white wires with meter to ground, stator is bad.

 

Well I pulled cover off and yes stator has about a 3 inch burned area on it.

NOW I cant get the cover to go back on. front has bolts lined up, back where the wires come out, is 1/2 hole to high. I have pryed, twisted, pulled partially back off, banged, Etc. Even pulled completely back off a dozen times.

 

Any ideas????

 

THANKS!!!

[frankd]

In my previous messages I told you that the stator should NOT be grounded.....2 days ago.

 

 

The magnet will pull the stator into it if you get a little to the side. Pull the cover all the way off and start again. Make sure your locating pins are installed. Don't force it, it will go on just fine.

 

Frank