Testing a rectifier.

My Harley came with an AGM battery. It lasted 5 years with very little maintainance. I would charge it once or twice during the winter. If I took it out of the bike and brought it in so it wasn't experencing the very cold temps I might have gotten longer on it.
Stanley that battery should work well for you. It has a few more cca's than a stock battery. It should start the bike a bit better.
Leo
 
Thanks for the reassurance. I looked quite a while online to get a good one. Can't wait to get it installed and see if that fixes my charging problem. Seems like it would do well with all the vibration of a xs. Thanks stan
 
Hey guys,,,I put the new AGM battery in my 78 special. This is where I got to. Lets say my multi meter is reading .2 volts low. So the battery fully charged is at 12.2 v. I lost .3 volts with key on, on the switched brown wire. Thats 11.9 v. I'm only getting 11.4v. on the green coming out of the new vr.115 regulator with no load, or no left ungrounded brush hooked to it. So I lost .5 volts just measuring the volts on the green wire just hanging by itself. When I hook the green from the reg. to the left ungrounded brush on the new mikesxs stator which is making contact on my new rotor from Mikesxs I am getting 10.4 when I measure voltage from the left brush to ground. Is that normal to loose so much voltage? It does eventually actually "warm up" the stator a spec to the touch. Which doesn't seem that out of the ordinary since it is grounding to the motor though right grounded brush. I started the bike and had only 12.2 v. on the new battery at 4k rpm. If you guys could tell me what I should do, I would be much appreciative, stan
 
The voltage at the brush should be very close to battery voltage. If not then you have a point of high resistance somewhere. Often in the key switch or in one of the connectors.
With a fully charged battery use you meter and check voltages along the peth from battery positive to the brush.
As in at the red wire at the key switch, the brown wire at the key switch. The wires after the switch the key needs to be on.
Another thing you might try is with the bike runing, meter on the battery run a jumper wire from the battery positive to the green wire at the brush. This sends full battery volage to the brush and should make the battery voltage rse up. With a bit of throttle the voltage will climb quickly, don't let the voltage go over 15 volts. This proves your rotor stsator and rectifier are working and the regulator isn't. Could be wiring.
Leo
 
I have only lost .3volts where the brown comes switched from the key. So the vr 115 input volts is just .3 lower than the battery. So why does the vr 115 put out on its green wire, .6volt less than it receives on its yellow and orange line voltage. And since haven't seen a wiring diagram of the reg., why does it have "2" hot leads going in? Thanks stan
 
That regulator was used on cars trucks and such, so to find an answer to that question you might look at a wiring diagram for one of the original vehicles it came on.
I have not used that particular reg, I used the R292 From an old Dodge. The one that needs the nylon screw mod. It works well. I also found out that miswiring it can short it out.
Leo
 
ok I will check that out. Don t I know about wiring something dc volts wrong. AC volts is my world. This is quite humbling. I am about push into the pond out back. lol Mr Retiredgentle knows about the vr 115. Maybe he will let me know. Thanks to you all, stan
 
Stan, I see this saga continues. Back in post #50, on March 8, you reported 12 volts on the green wire to the left brush, and battery voltage was up to 16 volts at 4k rpm. This was with your second VR-115 regulator. This tells me that your stator, rotor, brushes, and regulator are all working, except that your regulator seems to have lost its reference voltage signal. I've seen that occur on trucks and bikes, and it was loss of the ground to the regulator in both cases.

Now, you report that you only have 10.4 volts, on the green wire to the left brush. This is only giving 12.2 volts at the battery at 4k rpm. I'm going to tell you the same thing that Leo told you. You now must have a high resistance in the circuit that feeds current to the rotor.

Disconnect the battery positive cable from the battery. Make some resistance measurements. Measure the resistance of the main fuse/fuseholder i.e. from the battery positive cable to the red wire at the ignition input. Also measure (with the ignition key selected ON) from the red wire ignition input to the brown wire at the VR-115 input (same point as the orange and yellow wires on the VR-115). Those readings need to very low, such as 0.2 to 0.4 ohms.
 
Will do...It is saga isn't it? Same problem I have had since I got bike. Thank you guys for hanging in with me. I know you both have to be sick me and my one problem. Thanks a million,
 
Ok guys, I got a chance to do as you both told me. Battery unhooked. Measured from battery hot lead to 3 wire harness at the key switch red wire, power in and got .3 ohms. I meas. from same harness brown to the fuse box. Same .3 ohms. Your were both correct! Its a bad key switch. With the key switch harness unplugged the meas. was all over the place. So I'm buying a new one from Mikes for $33. So I made a 3 wire jumper and tied the red wire voltage in to the blue to taillight and the brown swtched out to the fuse block. Bypassed the key switch. Then I took new wire from the batt to the orange and yellow lead wires on the vr115 reg. 12.2 volts on new wire. Battery charged up with no load was 12.4 volts. Cables connected and key on {in this case, jumper plugged in} the batt reads 12.2. With no load on the vr115 green + voltage out, I only am getting 11.6 v. Green wire hanging without being hooked up. Thats -.6volts. Seems odd. Started the bike, head light "out" at 3 to 4 k rpm I got 13.1 v at the new AGM battery. Not 14+volt like anticipated but the best I have had so far. What do you'll think and recommend. Thanks stan
 
When you only measured 13.1 volts at the battery, did you wait 3 or 4 minutes for the battery to recover, after the large current drain of the starting motor?

Another way to test is to measure the actual rotor current flow. You can connect your VOM in series with the green wire, that feeds the left outer brush. Select the VOM to amps, 20 amp scale (or 10 amp scale if you have one). You should measure about 1.9 to 2.1 amps with engine at 1200 rpm. When you rev the engine to 3000 rpm the current should decrease to abour 1.0 amp. Those are real world numbers from my bike.
 
No I only ran bike maybe a minute. So many "loose" ends just hanging out I haven't run it that long in a while. Been waiting to get the charging issue fixed to button things up. But I can do that. The only way I've ever measured "current or amps" is with my "clamp on" current transformer type digital multimeter. My background is completely with AC voltage. This is new to me. I am not even sure which meter I should use to do that test. I have a digital multimeter, a Amprobe clamp on analog, and a cheap analog dial meter. I understand the hooking it up in series or "inline" with the circuit so the voltage goes "though" my meter. ? Always wanted to know how to measure DC amps. Thanks again
 
No I only ran bike maybe a minute. So many "loose" ends just hanging out I haven't run it that long in a while. Been waiting to get the charging issue fixed to button things up. But I can do that. The only way I've ever measured "current or amps" is with my "clamp on" current transformer type digital multimeter. My background is completely with AC voltage. This is new to me. I am not even sure which meter I should use to do that test. I have a digital multimeter, a Amprobe clamp on analog, and a cheap analog dial meter. I understand the hooking it up in series or "inline" with the circuit so the voltage goes "though" my meter. ? Always wanted to know how to measure DC amps. Thanks again

Yes, try it again, but wait to give some recovery time to the battery. Looking for 13 to 13.4 volts at idle and 14.1 volts at 3000 to 3500 rpm.

Stan, if you can work with AC, then DC is much simpler. A digital VOM or a cheap analog VOM will both measure DC amps. Just connect the meter in series (be sure to be selected to amps) and don't worry about polarity. If you have the leads connected the wrong way, the analog meter will swing the needle the wrong way, so you just select the reverse on the meter. A digital meter will just give a negative reading I believe.
 
Well I checked my meters to see if I could check DC amps and they won't do it. So I changed the fuse block out to one that Mikes sells. Did some other wiring and I took it for a ride a few miles at low "below" 2500 rpms, in case it was jumping back up to 16v like it had been doing in the past. After slow ride I checked the volts volts at low rpm around the 14 v. mark. But when I went back up to 3k rpm it would in short lived burst go back up around the 16v. Is that normal for it do that just for a few seconds and go back down? On a different subject, in my "attempt" to restore my wiring back to as close as I can, { because when I got it, it was hanging spider web} to original, I am looking at the factory service manual and its showing that the regul. and the rect. are being fed by the big red wire on "route to" the key switch. I am running the vr 115 and radio shack rects. How can they be hot all the time? So? can the brown wire from the key switch, handle adding the rect and reg on its load total? I feel so close, and all of you have helped me so much! Thanks
 
Firstly hello to one and all.
I'm working through my charging circuit because I'm only getting 1.5volts to
my battery at 2500rpm and after adjusting the voltage regulator right in managed to get to 7volts max I have a 1979 xs650 Special.
I've ordered two new bushes as they are only just above spec.

I'm after some advice in testing the rectifier with black probe on the black wire and moving the red probe between the white wire no reading.

Now with the red probe on the black wire and moving the black probe between the white wires I get a very fast reading more like a flash really some times quite low say 40 ohm then next around 140 ohm.
Does this mean its not working dead?
By the way all contacts are clean and the unit is out of the bike.
Any advice much appreciated

Hutzpah

Something wrong with your testing because the engine could not be running with only 1.5 or 7 Volts on the battery.
 
Well I checked my meters to see if I could check DC amps and they won't do it. So I changed the fuse block out to one that Mikes sells. Did some other wiring and I took it for a ride a few miles at low "below" 2500 rpms, in case it was jumping back up to 16v like it had been doing in the past. After slow ride I checked the volts volts at low rpm around the 14 v. mark. But when I went back up to 3k rpm it would in short lived burst go back up around the 16v. Is that normal for it do that just for a few seconds and go back down? On a different subject, in my "attempt" to restore my wiring back to as close as I can, { because when I got it, it was hanging spider web} to original, I am looking at the factory service manual and its showing that the regul. and the rect. are being fed by the big red wire on "route to" the key switch. I am running the vr 115 and radio shack rects. How can they be hot all the time? So? can the brown wire from the key switch, handle adding the rect and reg on its load total? I feel so close, and all of you have helped me so much! Thanks

No that's not normal. Your voltage at the battery should not exceed 14.5 volts at 3000 rpm. Stan, you must have a bad connection with your regulator wiring. As I mentioned once before, if the regulator loses its ground connection, the reg will default to full output to the rotor and cause high DC voltage to the battery. Where do you have the regulator ground connected to? Is it connected to bare metal of the frame? Make sure its not grounded to the battery box.

Only the rectifier is connected to the red wire that runs from the battery + (via a main fuse) to the key switch. The regulator gets its voltage source from the brown wire on the load side of the key switch (same electrical point as the supply to the fuse panel.)

The rectifier and regulator are not loads. The rectifier supplies DC current, and the regulator only controls current flow to the load which is the rotor field winding.

The rectifier runs hot normally, and thats why is needs a good heat sink. I hope you are using a heat sink. The VR-115 regulator does not generate much heat..............I have never found it to be even warm..............no heat sink required.
 
I have a no. 8 awg wire from the neg batt. term bolted to the frame, not the floating ungrounded batt box. A no. 12 awg stacked on that connection point going to the reg. It has to grounded well. And it is not hooked to the floating ungrounded battery box. I do have the aluminum heat sink with the heat sink compound between the two items. See if all this sounds correct to you. On the reg. vr 115 I have the orange and yellow hooked to the load side of the switch " brown" wire. The black is grounded as mentioned. Green out to the left ungrounded brush on alt. Right brush is grounded through its mounting screw to the motor and the black hooked to it goes up to the neg. The rad. shack rects wired like the online diagram. I am going to go hook the rect to the switched brown. Does the metal body of the reg. need to be grounded? Have not looked yet to see, how the motor is grounded and I guess could that effect it? Thanks again Saga Stan lol
 
Forget the "is the motor" grounded question. But have taken a short cut on the 2 rects. I have 90 degree female connectors "pushed on" not soldered going to the rects. I have the heat reducing tweezers to do it but was kind of wanting to see everything charge right before I do those 7 solder points. Could that also be a probem? Again appreciative.
 
The big red wire between the reg/rec and key does not feed power to the reg/rec. This is power from the reg/rec to the battery and key. A rectifier is a set of diodes. A diode is a one way valve. Power only flows one way. The diodes are wired so the thnree phase AC from the stator is rectified to DC that gets sent to the battery/key. If the diodes are ok then power can't flow from the battery to the reg/rec.
The brown wire from the key is used by the reg/rec as a voltage reference. As well as power to the rotor.
Let s use the stock reg and rec to explain the way the system works. Power on the brown wire goes to the reg. When the reg reads the voltage on the brown wire and finds it below the preset 14.5 volts it sends power out on the green wire to the rotor, through the rotor to ground. This creates a magnetic feild around the rotor. As the rotor spins this magnetic feild changes from positive to negitive. This change is what creates the AC voltage in the stator. This AC is sent to the rectifier and gets converted to DC.
Once the voltage on the brown wire reaches the preset 14.5 volts it stops sending power to the rotor. This stops the magnetic feild and stops the charging. Now the voltage starts dropping, once it drops below thw preset 14.5 volts the reg turns on the power and the chagre cycle starts. The mechanical reg cycles a few hundred times a minute. A solid state reg uses a transister to control the power flow to the rotor. Not being mechanical it cycles much faster. Thousands of time per minute. This faster cycling keeps the battery charged better.
If your reg is spiking the voltage to the battery the first thing I would check is the ground for the reg. If the ground is intermittent, this will give you the spike. As RG said, the reg needs a good ground.
Loose connections on the rectifier shouldn't cause voltage spikes, voltage loss, yes. I have my Radio shack rectifiers hooked up with plug on connectors. Working that way for several years now.
The rectifier has the three white wires from the stator, a red to the battery and a ground. What are you going to hook to the brown wire?
Leo
 
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