Regulator / M-Unit Blue headscratcher

[QWERTYMage]

OK. This has a lot of words... I'll keep it as clear as I can.

The Bike:
1975 XS650b. Stock Alternator (field excited).

The Variables:
M-Unit Blue (I cooked my M-Unit V2 - moron that later). Antigravity 4 cell battery (Cooked an 8 cell and a 4 cell too - this is getting old and expensive). Oregon Cycle Works VRREM7-XS Regulator/Rectifier (It worked great before - http://www.oregonmotorcycleparts.com/Reg_rec_units.html )

The History:
Meltdown #1 - I had the bike hooked up to an m-unit V2 and an antigravity 8 cell. It ran like a top, took long rides, and behaved like I knew what I was doing. The Reg/Rec is handmade and table tested. Worked like a champ. The test wire was hooked up to he V2's Aux output (along with the ignition). I had to remove the carbs to clean them out and upon putting the bike back together, didn't tighten the regulator's ground wire down and it vibrated loose. The 8 cell melted down (THAT was fun) but the V2 came out OK. My best guess was that without consistent power because the ground wire wasn't completely engaged, it drained the battery beyond it's limits, then when it started getting intermittent charge, it 'sploded a bunch of smoke and juice.

Meltdown #2 - I got a 4 cell Antigravity battery (not running a starter) and ran the bike - until the battery 'sploded a bunch of smoke and juice again. This time, the m-unit v2 was cooked too. Upon inspection, my ground wire was properly tightened down, but the Regulator's plastic block was worn out, and the metal tang holding the metal connector was pushed out instead of connecting - I couldn't see it and didn't test the connection before ruining the m-unit. THAT was not fun.

So, here I am. I've got PTSD from all this and am testing the balls out of my system. New M-Unit blue, new Antigravity 4-cell. I have replaced the plastic block (and the connectors that go in it). and I'm coming up with a regulator problem... the Regulator sensor wire is hooked up to the Aux 2 output.

The Good:
The Blue turns on fine. The bike starts and runs fine at idle. I've tested ALL the wires at the regulator connector block to make sure they are connecting correctly and are in fact passing current as they should. They are. I've tested the regulator by turning on power and testing for current at the block on the positive and negative (12.4 volts - instructions on testing the reg were grabbed here: http://chris-kelland.squarespace.com/regrect-unit-xs650/ ) so this tells me the regulator is passing juice to the brushes as it's intended.

The Puzzling:
To test to make sure the regulator is limiting the max charge to 14.5v, I hook up a meter to the battery tender (direct to battery) and rev the engine to 3k rpm. The meter read

past 16v and the m-unit started the blast-the-horn-shunt process it does when you are about to make a costly mistake again. I very quickly killed the engine and pulled the fuse (20A) just in case.

The questions:
1. The Regulator isn't regulating. Is it possible I somehow cooked the sensor circuit? (logic is telling me this is the case) Is it hooked up to the wrong output on the m-unit blue?
2. The batteries were drained and damaged (no strong negative circuit on the regulator) then exploded when the minimal charge was put into them? I wanna rule out something else entirely.

Thanks for the help. Ride safe.

 

[XSLeo]

I don't know much about your M-Unit , I do a few things about charging systems.
Are you using the stock mechanical reg and separate rec? If so you should upgrade to a solid state unit.
In the stock sert up the brown wire to the reg/rec should read battery voltage when the main switch is on. The reg reads the voltage and if low sends full battery current to the rotor via the green wire. At the brushes the current flows through one brush, through the rotor, out the other brush where it grounds to the stator. The black wire serves as a harness ground.
The Later combo reg/rec works by having battery voltage applied through a brown wire to one brush, through the rotor, out the other brush on a green wire to re/rec where it grounded. The combo reg/rec reads battery voltage off the brown wire. If low it uses a transistor the turn on current flow by grounding the green wire.
Over charging depends on the voltage the reg/rec reads. If your battery reads 12.5 with the switch on. Then it reads 11.25 art the reg/rec the reg/rec thinks the battery is low. So it turns on the current flow trying to charge the battery. With the low reading at the reg/rec it will overcharge your battery.
Check the voltage at the battery and at the reg/rec If more than about .5 volts low you have a bad connection on the power side.
A poor ground at the reg/rec can also read as low voltage at the reg/rec. Check your grounds. Clean bare metal to clean bare metal. Any paint or such can act as an insulator.
Leo

 

[QWERTYMage]

Thanks for the reply, Leo. I'll definitely be checking this: "If your battery reads 12.5 with the switch on. Then it reads 11.25 art the reg/rec the reg/rec thinks the battery is low. So it turns on the current flow trying to charge the battery. With the low reading at the reg/rec it will overcharge your battery."

For those reading through: Yes, it is the stock stator and brushes for a '75. It is a new combo reg/rec unit. Solid State. Made by http://www.oregonmotorcycleparts.com/Reg_rec_units.html (see original post) Grounds are clean, paint-free, and connections in the plug are strong with low resistances.

 

[mrtwowheel]

I suggest you get back with Oregon. I suspect that your wiring, bad ground, has wrecked the regulator and the batteries. Oregon can help you confirm this. Even though it may be your fault, I would take advantage of his lifetime warranty, that's what you paid all of that money for. If he helps you confirm that the regulator is bad, but not covered by the warranty..........he uses a Fiat regulator that was available on ebay for about $9 a while ago.

Scott

 

[5twins]

Some of their reg/rec units use that Fiat regulator, the ones that require a type A ground switching regulator. Yours is not that kind. Yours needs a type B power switching regulator. I don't know what kind of regulator they use for that but you can use an automotive VR115 or one of it's equivalents.

What's up with that M-unit? I thought it was supposed to prevent stuff like this. For $400 I'd be pissed. It strikes me as nothing more than a fancy VERY expensive fuse box, and it's not even good at that, lol.

 

[QWERTYMage]

I have a convo going with Mr. Oregon.

Regarding the m-unit: It works great (not anywhere close to $400, tho) but it ain't idiot proof. It's one weakness is overcharging and I did just that. Handles faults like a champ. And didn't require a giant pile of wire and relays to make it work. Just a competent person and a good regulator.