Topic: I keep burning out my regulator/rectifier. Anyone know why??

[tarsnake]

Hello fellow riders,

I've burnt out my regulator/rectifier twice now.  I'm trying to figure out why.  The bike has been serviced by a very experienced mechanic and other than the R/R issue, the bike runs very well.  Here's a brief history. 

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The bike was rained on heavily 3 years ago.  I had to replace some components of the points system.
A year later, the battery wasn't charging so I checked the stator and rotor.  Both were fine.  The mechanic also checked and confirmed it was good.
The points ignition system was replaced with a Pamco electrical ignition last year. 
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My suspicion is that the stator is buggered but still works, kind of.  If the R/R is burning out, would that mean there's too much voltage being fed to it from the stator? 

Any insights would be much appreciated.

[RJ CB450]

Honestly, check the ground first.  That is how the R/R discharges.  Could be some corrosion preventing it from discharging properly.  With the stator and rotor, usually is a problem with loss of charge.  Not sure what could cause it to generate more outside of insufficient discharge.

Also, any mods or minor changes causing it to not be able to properly keep cool or cause it to run hotter?

A guy on another forum I am with actually uses a computer fan on the R/R to improve airflow due to the hot climate.

[Spanner 1]

The clairvoyants will be along shortly to figure out what model and year your bike is  ... might need that info to try and help...

[tarsnake]

Thanks Old Timer.  Forgot about that.  CB750k 1978.

Mods on the bike: pod air filters, pamco ignition, 4into1 exhaust

I'll check the ground tomorrow and report.

[Spanner 1]

So first off it's not possible for your stator to ' feed too much voltage ' to the regulator..... and your bike does not have a rotor that can be 'checked'. The charging system on your bike consists of a stator ( which is a wire winding in segments ), a field coil and the rotor which spins between them. Do you have a service manual ?
My first question to you would be ; Have you charged the battery ( in the bike ) with a car type charger and if so what amp. setting did you have it at ?

[Vinhead1957]

I would go through all the connectors and check for corrosion and over heated wires. Brown is a bad sign.  These bikes have minimal wiring standards and tend to cook components. 

[pamcopete]

tarsnake,

Well, the so called R and R is actually two separate devices. The regulator and the rectifier. The regulator provides current to the field winding to produce a magnetic field that the stator windings convert to a voltage and current used to charge the battery and run the electrical system. If the field winding is much less that about 7 Ohms, excessive current will be needed from the regulator and that could eventually fry the output transistor of the regulator. So, start by measuring the field winding resistance with the field winding disconnected.

If it is the rectifier part of the R and R that is fried, then that would be indicative of something drawing a heavy load. Could be a partially shorted headlight filament for instance, or could also just be a bad battery that is drawing too much current. Check the six diode arrangement of the rectifier with an Ohmmeter looking for a low resistance in one direction and a high Resistance in the other between the white wires and the red and black wires of the R and R.

Generally, if the regulator transistor is fried, you will not get any output from the alternator because there would be no field current. If one of the diodes in the rectifier is either shorted or open, then you will still get an output from the alternator, but it will be less than the 14.5 Volts that it is supposed to be.

[JakeB]

I burnt out a brand new reg/rect. Turns out the sequence of wires in the harness for the reg/rect, are different from that of the harness coming from my stator. Luckily it was under warranty and the new one works fine. Just double check that all your colors are matching up in the connected harness. Easy to overlook.

[tarsnake]

So first off it's not possible for your stator to ' feed too much voltage ' to the regulator..... and your bike does not have a rotor that can be 'checked'. The charging system on your bike consists of a stator ( which is a wire winding in segments ), a field coil and the rotor which spins between them. Do you have a service manual ?
My first question to you would be ; Have you charged the battery ( in the bike ) with a car type charger and if so what amp. setting did you have it at ?

The bike has a brand new battery so that's not the issue.  I do have a trickle charger that I've used in the past and keep it at 2Amps when charging my bike battery.
I have the service manual and went through all the steps, tested the stator and the rotor, both are good.  The mechanic confirmed it also.

I replaced the R&R wit a solid state unit that has both in one..

[tarsnake]

I burnt out a brand new reg/rect. Turns out the sequence of wires in the harness for the reg/rect, are different from that of the harness coming from my stator. Luckily it was under warranty and the new one works fine. Just double check that all your colors are matching up in the connected harness. Easy to overlook.

Oooo, that does sounds like it could be very easy to overlook.  I'll check that for sure.  Thank you.ß

[tarsnake]

tarsnake,

Well, the so called R and R is actually two separate devices. The regulator and the rectifier. The regulator provides current to the field winding to produce a magnetic field that the stator windings convert to a voltage and current used to charge the battery and run the electrical system. If the field winding is much less that about 7 Ohms, excessive current will be needed from the regulator and that could eventually fry the output transistor of the regulator. So, start by measuring the field winding resistance with the field winding disconnected.

If it is the rectifier part of the R and R that is fried, then that would be indicative of something drawing a heavy load. Could be a partially shorted headlight filament for instance, or could also just be a bad battery that is drawing too much current. Check the six diode arrangement of the rectifier with an Ohmmeter looking for a low resistance in one direction and a high Resistance in the other between the white wires and the red and black wires of the R and R.

Generally, if the regulator transistor is fried, you will not get any output from the alternator because there would be no field current. If one of the diodes in the rectifier is either shorted or open, then you will still get an output from the alternator, but it will be less than the 14.5 Volts that it is supposed to be.

Hey Pete,

I replaced the reg&rec with a solid state unit.  That went.  Then the mechanic replaced it and it went again.  Not sure if what you wrote applies to a solid state unit.

[pamcopete]

tarsnake,

Well, I did mention a transistor in the regulator...

[dave500]

maybe the wrong rec/reg unit?one to suit a permanent magnet type will be dumping excess voltage furiously hooked into an electromagnetic field type system,make sure its the correct type of unit not a "universal" type?

[tarsnake]

Tarsnake - you're all over the place...

You are now ringing an aftermarket Solid State, Regulator-Rectifier. And you say that the previous "fried" and it too was replaced under warranty? What year bike and model? What brand Reg/Rec?

Most common brands of R/R have exact match colors to the R/R for the specific alternator for your bike. These generally plug into each through a 6-gang block connector. Hard to mess that up...

The R/R controls the amount of voltage sent by your alternator to the battery. Are you having issues with your battery holding a charge? Even as a result riding above 3,000 RPMs for extending periods of time? If so, you really need to perform some basic electrical troubleshooting.

Do you have some pictures of your instal that you can post? Pretty uncommon for solid state units to "fry" or go bad repeatedly, unless, there is a major electrical grounding problem on your bike, and/or your wiring is complete butcher job.

Yeah calj737, I know I'm all over.  I'm trying to cover all my bases but don't know where to start or end.  "breath" 

When I was riding last night (for about 2 hours), my turn signals started to get dim and stopped working altogether as well, my horn stopped working.  In addition, my rear turn signals didn't illuminate when I turned on the bike but they blinked when I signaled (when the battery isn't too drained).  I took all those as signs my R/R was pooched again.  I did some basic electrical troubleshooting as you said and discovered a few things.

I checked the continuity of the ground of the R/R.  There is continuity.
I ran the bike and tested the voltage at the battery.  At 6000rmp I got a reading of about 13.7V.
At rest (not running), I got a reading of around 12.4V

Could it be I just ran the bike 'tired' and it needed a rest?  Are these symptoms of some other issue I'm not aware of?  I'm going to take it for a ride and see if I get any issues popping up again.  Sorry guys, I don't mean to waste anyone's time here.  I'm no expert (obviously) but I really appreciate all the feedback.

[scottly]

Hello fellow riders,

I've burnt out my regulator/rectifier twice now.

I doubt you "burnt out" your R/R twice; much more likely that replacing the R/R never fixed the original problem. Check the voltage drop between the battery plus terminal and the black wire that goes to the reg portion. To do this, place the red test probe of the meter on the battery +, and the black meter probe on the black reg lead, with the ignition switch on, motor not running.

[tarsnake]

Hello fellow riders,

I've burnt out my regulator/rectifier twice now.

I doubt you "burnt out" your R/R twice; much more likely that replacing the R/R never fixed the original problem. Check the voltage drop between the battery plus terminal and the black wire that goes to the reg portion. To do this, place the red test probe of the meter on the battery +, and the black meter probe on the black reg lead, with the ignition switch on, motor not running.

When I perform that test, what is an acceptable/not acceptable voltage drop.  Or in other words, what exactly am I looking for?

[scottly]

If the meter reads .5 V, your wiring harness connections and switches are in very good condition, 1 V is marginal, but anything over 1.5 V is a smoking gun.

[tarsnake]

At rest, fully charged, your battery should have at least 13.1v.

Measure the voltage at the following RPMs:
Rest
2,000
3,000
4,000
5,000

You should be seeing at least 13.4v by 3,000, and as much as 14.4v at 5,000. If not, what you are witnessing is not enough charge coming to the battery. It can also be indicative of a battery that is not "good" or poorly grounded. Does your battery NEG wire, run to the rear, upper bracket for the motor? And, does it connect directly to bare metal, or through paint/powder coat to the frame?

Trickle chargers only "maintain" batteries, they don't really fully charge them. To fully charge them, take your bike onto an open road, or highway, and run it above 5,000 RPMs for at least an hour. Upon returning home, test the voltage at the battery with engine and key off. Then, repeat that reading 2 hours later. If you don't have at least 13.1v, replace the battery.

If you have a standard lead acid battery, and ran it down to a very low charge, you may have evaporated some of the acid out. Sometimes, you can revitalize it, but I'd recommend replacing with a quality AGM type battery. Be sure it's at least a 12 Amp Hour rated battery.

These old Hondas don't produce any charge when idling, and virtually no extra charge below 3,000 RPMs. So if you are testing the bike in the garage, then you're draining the battery. Or, driving around town at low RPMs, especially with lights on, you've got a drain again.

See if some of that helps troubleshoot your woes. Take some pictures if you're unsure about what you have, or concerned about how you're wired up. Lots of folks here to help-

Thanks calj737.  I just got back from a ride and the bike is performing similar to how you described.  When I'm on the highway or long stretches, the turn signals are fine and the horn works no problem.  When I'm start and stop in the city, my signals dim and stop blinking and the horn doesn't even make a squeak.  When I tested the battery this evening, I was well up to 6000RPM and the voltage was nowhere near 14.5 or 15.  As a matter of fact, it was slow to climb and only made it 13.6V when sustained at 6000RPM.  That battery is brand new as of 2 days ago so I'll do a thorough check like you described and see what I find.  Thanks for your insights.  I'm feeling a little better about the directing I'm going in now.   

[tarsnake]

If the meter reads .5 V, your wiring harness connections and switches are in very good condition, 1 V is marginal, but anything over 1.5 V is a smoking gun.

Thanks Scottly, I'll put that on the to do list tomorrow and report back.  Thanks for the advice! 

[scottly]

At rest, fully charged, your battery should have at least 13.1v.

Sorry Cal, but I don't agree; a fully charged flooded lead-acid lead acid battery in good condition will typically read 12.6 to 12.8 V after 24 hours rest.

[Bodi]

The only way you could burn out a reg/rect is by miswiring. Or boosting the bike with reversed power, we'll assume you didn't do that. Or using the wrong (incompatible or undersized) reg/rect on a bike, I assume this is not an issue either.
The regulator takes system power from the ignition switch and does just 2 things with it: compares it to the desired voltage, and sends power to the field coil unless the system voltage is above what's desired. The regulator's mechanical switch or electronic circuitry is capable of powering the field coil indefinitely without burning out.
The field coil creates a magnetic field coupled to the rotor, which has magnetic poles that form alternating N and S poles around its circumference. When the rotor turns these poles sweep across the "delta" three phase stator coils and produce AC power.
The rectifier takes the 3 phase AC from the alternator stator coils and converts it to pulsating DC power. The battery smooths out the pulsations, acting like a capacitor would in a simple AC-DC power supply. The 6 diodes in the rectifier are rated to continuously handle the maximum output current of the alternator. They do produce heat and need sufficient cooling to avoid failure from overheating.
If all the components are wired correctly the regulator and/or rectifier will not "burn out". The voltage drop at the regulator matters not: it will affect the charging ability and can cause battery overcharging - but low voltage will not damage the regulator.

[pamcopete]

A conventional leads acid battery is considered to be fully charged at 12.6 Volts with no load after a rest from charging. The voltage of 13.1 Volts is the recommended voltage to maintain a battery during prolonged storage and that is the voltage that battery maintainers are designed to keep the battery at as the battery will be chemically inactive at 13.1 Volts.

Here is a typical load for a motorcycle:

Headlight, low beam = 40 W
Tail Light = 8 W
Ins. Lights 3 X 3.4 W = 10 W

Total lights = 58 W/14.5 V = 4 Amps
Ign. Coils (points) 14.5 / 4.5 = 3.2 * 50% = 1.6 Amps
Regulator 14.5/5 = 2.9 Amps (current decreases as the rotor heats up)
Reserve to charge battery 2 Amps

Notice that the reserve to charge the battery is only 2 Amps with the alternator producing its maximum capability. Coincidentally, 2 Amps is also typical for a trickle charger and the battery should be charged for several hours at 2 Amps to fully restore it to a fully charged condition, so you can either hook up your trickle charger overnight or ride down the interstate for several hours to fully charge the battery. One hour of riding won't do it. In normal usage, your battery will slowly get to a low charge state due to stop and go type of riding where the battery discharges at every stop light, but does not get enough of a charge in between lights because you are not necessarily winding it up to 3 to 5 K RPM's where the alternator can produce enough excess current. I typically put my motorcycle batteries on trickle charge routinely because I know they are always in need of a charge.

[ekpent]

If it is a lead acid battery and new, did you after putting in the acid and letting it rest a bit give it a good charge before installing in the bike per from the instruction sheet ?