Topic: CB400F charging issues using M-Unit **sort of fixed**

[Dave87]

G'day All, I have been an avid reader of this forum for some time now and it is only now that I am posting my first post.

Firstly I cannot thank those more knowledgeable who post on here answering to the many questions and queries. The time and effort you put in is really very much appreciated! We would be lost without you.

The story: back in 1979 my dad rode a 1975 CB400F  from Texas up to Alaska. He sold the bike before he came back to Australia, although old mate who he sold it to never received the rego papers apparently.
Skip ahead a couple decades and Dad finds this American imported 1975 honda that is identical to the one he rode in the States (could it be the same one..?). Naturally he struck a deal and bought it.
He owned if for a while before life made him sell it.
12 years later, I'm talking to Dad about bikes and he tells me the bloke he sold his bike to is wanting to sell a pair of CB400Fs... So of course I went down with a mate and bought one each, me buying back my old man's.
Since then I have been working on it, not a resto but a custom job in a way that I liked and that still threw back to it's classic origins. As it had been sitting under a tarp for almost 10yrs it wasn't in great shape once I started breaking her down.
Well she's now all but done.

So the issue.

I am not getting a signal current/voltage to activate the field coil via the white wire coming from my rectifier/regulator.

The setup I'm running with is an M-unit, an Anti-gravity 13V, 4 Cell battery and a Forsetti Rectifier/regulator

Regulator black wire to M-unit Lock.
Regulator white wire to field coil white
Reg/Rec green wire to earth
Reg/Reg red to Battery + (also M-unit power supply as it is all connected)
3 Yellows to 3 yellows.

I have read and read and triple checked my wiring and connections and everything seems in order. The Alternator and Field Coil are both good. I ran all the resistance and continuity  checks in manual and any extra that I could think.

I can get the Alternator to work by bypassing the Regulator which indicated to me that it must be a dud. I bought a new one and hooked it all up only to have the same problem. I then hooked up the Regulator straight to a 13v car battery and hey presto the white wire came alive, indicating to me that the Regulator is not actually cooked.

Is there anyone out there that knows what could be the issue here... I have heard that it might not be enough grunt (despite having 12.8 +- V to the Regulator Black wire) to trigger it to activate.

Buggered if I know...

Thanks a heap!

****In short check that the Regulator/Rectifier is not earthing out to the frame! I wish I had known earlier! ****
 

[RAFster122s]

Do you have a diagram of your wiring scheme with the M-unit? That would be helpful.
What is the wiring for your rectifier/regulator...all the connections...where do you have them hooked up?

[calj737]

The m-unit is not involved in the charging of your bike. The black wire as used is showing switched voltage to activate the m-unit and provide a reading of the stock harness keyed voltage. So where is the BLACK from your key running to? That should go to LOCK so the Regulator black sees the actual battery voltage on the same line.

Or move Regulator black to AUX and get the switches voltage status there.

[calj737]

The other thing, the Regulator Green wire should connect to the Green within the stock harness coming from the charging bundle, not directly to ground.

Confirm your stock charging bundle is: 3 Yellows, 1 White, 1 Green. Those all connect to your Reg/Rec. The Black and Red go to LOCK and battery POS. Many new Reg/Rec units also have a second Green for a device ground, but sounds as though yours needs a physical mount as its ground. Just make sure your mounting screws of the new unit as getting good, low resistance to chassis with near 0 ohms.

[Dave87]

Thanks for your quick replies guys,

For better or worse, I completely rewired the bike to work in with the M-unit etc...

The Reg/Rec has 3 Yellows, 1 Green, 1 Red, 1 Black and 1 White. It is designed to be a direct replacement for the regulator and rectifier using the original harness.

The way I have it wired up is as follows;

Alt Yellow x3 - Reg/Rec Yellow x3
Alt Green - Earth (bike frame)
Alt White - Reg/Rec white
Reg/Rec Green - Earth (same point on bike frame as the 'Alt Green'. Both read 0 ohms)
Reg/Rec Red - M-Unit +ive which is also a direct link to Battery +ive
Reg/Rec Black - M-unit LOCK (this is where my Key wire is also located so it reads the same. When I turn the key, the light on the M-unit illuminates. AUX comes on with the Kill Switch.

I did try placing the Reg/Rec Black into the AUX but it didn't make any difference.
It is interesting what you said about earthing the Reg/Rec body as mine only has the one Green. I'll try earthing the body out the the frame and see if that makes a difference.

Thanks a heap to both of you, I greatly appreciate it!

[Dave87]

Here is the Wiring Diagram we get with the M-Unit. Just for Info.

Cheers.

[calj737]

So with the key OFF, what voltage do you have at the battery terminals?
What voltage do you see from key BLACK heading into LOCK?
If you directly connect the Alternator GREEN to Reg/Rec GREEN, what happens?

When you turn your key ON, both LOCK and AUX should illuminate. Your statement that KILL controls AUX has me confused.

[Dave87]

Depending on how long I have been playing around with it but I usually have between 13.4V and 12.5V at the battery and about 0.5V less coming from the Lock. My guess it that the M-Unit uses a bit in some way.

What about current? If the M-unit wasn't allowing enough current through to activate the regulator side of things, could that be a issue? just trying to think outside the box.

If I just connect the Reg/Rec GREEN to the Alt GREEN, how will it EARTH? They are currently share the same earthing point on the frame and are in fact contacting each other so in theory it should all be the same right?

I connected my kill switch up as per the M-unit manual. on the CB400F it is a toggle switch so to activate the coils the KILL needs to be ON, thus providing the power from the AUX to the coils. rotating the KILL to OFF kills the engine by removing power from the coils by using the AUX port.

The LOCK purely allows the M-Unit to be powered up. That's why it should be a good spot for the Reg BLACK to go, well both the AUX and the LOCK should have worked in the same way, right?

Sorry that it's not a simple problem.

[calj737]

Depending on how long I have been playing around with it but I usually have between 13.4V and 12.5V at the battery and about 0.5V less coming from the Lock. My guess it that the M-Unit uses a bit in some way. nope, you're seeing voltage drop through your key switch.

What about current? If the M-unit wasn't allowing enough current through to activate the regulator side of things, could that be a issue? just trying to think outside the box. nope again, the m-unit is outside the charging system. The BLACK from R/R being connected to LOCK is reading the switched power state from KEY BLACK (if that's where you ran that wire?).

If I just connect the Reg/Rec GREEN to the Alt GREEN, how will it EARTH? through the R/R body and its mounting hardware. In theory, as you have it should work, but since it doesn't, why not test some different connections 

They are currently share the same earthing point on the frame and are in fact contacting each other so in theory it should all be the same right?

I connected my kill switch up as per the M-unit manual. on the CB400F it is a toggle switch so to activate the coils the KILL needs to be ON, thus providing the power from the AUX to the coils. rotating the KILL to OFF kills the engine by removing power from the coils by using the AUX port. this is correct. It differs with how you described it last time which is why I asked? Nothing "kills" the power to AUX except de-energizing the m-unit. There is no means of simply energizing the m-unit and NOT having AUX conduct power. Just making sure that's clear. Wiring your stock KILL switch as a coil interrupt is not only prudent, but it behaves as a stock bike. Good deal.

The LOCK purely allows the M-Unit to be powered up. That's why it should be a good spot for the Reg BLACK to go, well both the AUX and the LOCK should have worked in the same way, right? correct. If you read the voltage at LOCK and compare it to AUX, you should see exactly the same reading. If that reading is 0.5v less than the battery, you're seeing resistance through the harness and key before it hits LOCK. This should actually overcharge your battery, not under charge it. This is why I believe your wired connections to the RR are not correct.

Sorry that it's not a simple problem. oh, but it is. Determine which wire is the offending cause is the challenge because at the moment, only you are sitting in front of the bike.

Is there a means of you posting a few pictures? Have you confirmed the wires exiting the stock stator are all clean, connected properly, and carry AC voltage?

Simply attaching different components to different vehicles and batteries isn't troubleshooting. You need to use a meter and diagnose things specifically with exact readings. That will tell you what is wrong, and where it's failing.

Simply use this flowchart and report your findings.
http://www.electrosport.com/media/pdf/fault-finding-diagram.pdf

[scottly]

If I just connect the Reg/Rec GREEN to the Alt GREEN, how will it EARTH? They are currently share the same earthing point on the frame and are in fact contacting each other so in theory it should all be the same right?

Both the green reg wire and the green Alt wires are indeed connected to frame ground (Earth). With the stock wiring harness, the solid green wires are all connected to frame ground, either at the coil mount under the fuel tank or near the battery under the seat, depending on model. If the green Alt wire is connected only to the green reg wire, the system won't charge, and is a common mistake when noobs try to wire a system from scratch. Your reg/rect unit does not need to have the body grounded, as clearly stated in the instructions you posted.
Try connecting the reg black wire directly to the battery + terminal. (Disconnect after testing, lest the draw from the field drains your battery)

[calj737]

Both the green reg wire and the green Alt wires are indeed connected to frame ground (Earth). With the stock wiring harness, the solid green wires are all connected to frame ground, either at the coil mount under the fuel tank or near the battery under the seat, depending on model.

This statement does not agree with the stock diagrams. The alternator wiring runs to the stock Regulator (as shown in the diagram), not to the coil mount. Sooner or later within the harness, some models do terminate their grounds there, but the charging system routes the alternator green to the regulator long before it goes elsewhere.
http://www.cmsnl.com/classic-honda-fansite/honda_wiring_diagrams/CB400F.jpg

[scottly]

Learn how to read a schematic, Cal. All solid green wires on Honda's are connected to frame ground. Ground is ground, the whole Earth 'round.

[calj737]

Learn how to read a schematic, Cal. All solid green wires on Honda's are connected to frame ground. Ground is ground, the whole Earth 'round.

I know how to read a diagram. What I wrote and what you wrote differ per the diagram as I said. And, these aftermarket RR's often have their GREEN wire preconfigured into the block connector opposite the alternator GREEN wire, indicating they connect together directly. The fact that they both terminate to ground is not in question. So spare folks your patronizing attitude and offer them your wisdom. They benefit from the latter and don't need the former.

[calj737]

Dave - It sounds far more likely that the Yellow wires are your culprit. So, have you confirmed they are clean, undamaged and fully connected all the way back to the alternator? They carry AC voltage and they need to carry enough voltage to the Rectifier to charge your battery.

You installed unit #1 on your bike and it didn't work.
You replaced unit #1 with a new unit #2. Same results.
You installed unit #2 on a different vehicle and the unit worked.
Reinstall on your bike, doesn't work.
The Black is seeing +12v on LOCK. Regulator is functioning properly.

These symptoms point towards your bikes Yellow wires. Use a meter and the flowchart linked to perform the AC voltage tests. Then post your results.

Pardon the romper room stuff between Scottly and me. He's a very bright guy but often misses his spoonful of sugar.

[Dave87]

Thanks for the continued support guys!

I will post a rough wiring diagram of how I have the charging system set up.

As for testing the Yellows and the coils (both field and alternator), I have carried out resistance checks and continuity checks on all IAW the workshop. They came back in spec and all connections were solid.

The problem I'm having is that power is getting to the R/R from the M-unit via the BLACK but I'm not getting anything out of the WHITE which should be used to activate the field coil.

I'm wondering if the M-unit is some how not allowing enough CURRENT through to the R/R to allow the circuitry to send it through to the Field coil? Anyone know how these things work internally?

[calj737]

Resistance and continuity checks are insufficient to determine the health of the Yellows. You must verify the AC voltage on them.

As for the m-unit, it is NOT involved in the charging or status. You tested the voltage at the battery and at LOCK and AUX and found them to be equal (within 0.5v). That is indication that the m-unit is seeing only what the battery is producing, and the Regulator Black wire too.

You can perform the AC voltage tests per the flowchart I linked, and you can perform Scottly's recommendation of connecting Regulator Black to battery POS. I doubt this will yield a different result though. I suspect the Rectifier is not seeing what is necessary to produce the current for the battery to charge.

[scottly]

I can get the Alternator to work by bypassing the Regulator

 

This would rule out the yellow stator wires, and the field coil. How exactly did you bypass the reg?

[Dave87]

Here is the wiring of how I have the charging system hooked up. I think it is pretty accurate...

To bypass the Reg, I just made up a jumper wire to go from the LOCK terminal to the WHITE field coil wire.

By using this method I managed to get the YELLOWS give me some voltage readings. I can't quite remember what they were exactly but I know that once I hooked the 3 YELLOWS up to the Rectifier it was producing between 13ish V to 14.5ish V depending on RPM.

I currently am not with the bike so further testing and trouble shooting will have to wait for the weekend but keen to hear of any more thoughts you might have.

Thanks again!

[calj737]

I don't see a wire from your KEY switch to LOCK on the diagram. Is it missing on your bike or missing in your diagram?

What your diagram should look like is more like this

[Dave87]

Ah my bad.  It's missing on the diagram. Sorry about that.

[calj737]

By using this method I managed to get the YELLOWS give me some voltage readings. I can't quite remember what they were exactly but I know that once I hooked the 3 YELLOWS up to the Rectifier it was producing between 13ish V to 14.5ish V depending on RPM.

That demonstrates to me that the Regulator is functioning. Else, you should have had as much as 18v heading to the battery.

You posted that you "got the Alternator to work" but later swapped out that unit. Then you tested this unit against a car's charging system and it worked. So back to your bike, and it doesn't work. The only common element is your bike and I still don't see how you have verified the Rectifier side and voltage from the alternator. Maybe Scottly has a different opinion.

I guess we will wait unit this weekend to get further updates.

[Dave87]

Sorry I may have confused you. I swapped the Reg/Rec out with a new item. It is still the original Alternator. I guess you could be right Cal in saying the Alternator is not putting out enough Volts due to it being slightly old etc. But if you could explain how this would stop power been sent to the WHITE signal wire that would be great. I think I must be missing a concept.

The Rectifier side of the R/R is clearly working as it is putting out DC. The Regulator is still an unknown I guess as the only way I have managed to get the field coil to work thus far is to jumper past the Regulator (jumping the black to the white prior to reaching the R/R)

I too previously came to the conclusion that it must be the BIKE and my wiring. So to try and isolate the faulty wire, I systematically went throught and bypassed my original wires at each connection. I even pulled apart my plugs and triple checked them all.

Cheers mate.

[calj737]

Well, you've posted a number of different things as results from different units, and different vehicles. So, from my understanding and as best I can sort it all out, with this unit:

- you bypassed the "regulator" side by jumping White to LOCK.
This is inconclusive because LOCK will see voltage from the key which is switched 12v. The battery then saw 13-14.5v which is a function of the Regulator. Yes, I concur that the battery seeing growing voltage would indicate the Rectifier is producing DC voltage.
- but you also used this same unit on a donor vehicle and everything worked normally. Correct? So we go back to your bike.

Something from your diagram, recollection and the physical bike is not agreeing to the results you're getting. If you were to use the diagram I linked, you would see that you can Ohm out correctly, get the proper DC Voltage, but still have a fault at the stator if the AC readings are too low. That's been my point. Speculating (on my end) won't get us any nearer to the answer. It takes 15 minutes to run through those tests and they will conclusively tell you if any component or connection on your bike is faulty. It could also be faulty diodes within the RR, even though it's new (again).

And, the BLACK wire from the RR could be the problem with how it's installed at the m-unit. Are you using the stock key switch? A relay? The m-lock? If so, move BLACK to AUX and test again. I've seen the m-lock cause issues with RRs when both share LOCK.

[Dave87]

Ah ok thanks again Cal.
I haven't had a chance to try your troubleshooting as I'm not with the bike atm. I will give it a go this weekend and let you know how I go. I'm using the stock key switch. Moving the black from LOCK to AUX made no difference.

Oh and just to clarify, I tested the Reg on a Car Battery not a  donna vehicle. Both R/R are brand new also.

Thanks a heap for everything. I'll let you know how the testing goes.

[calj737]

Oh and just to clarify, I tested the Reg on a Car Battery not a  donna vehicle. Both R/R are brand new also.

So can you explain how you performed this test? What was producing the AC/DC voltage that you "regulated"? Or was this simply running RED and BLACK to +/- of the battery?