Topic: Recharge Problem

[YoungBlood]

I know this is a common topic - I've read up on a good number of posts and I've been trying to troubleshoot alone, but I need some help here.

I just cleaned and greased the 8 prong connector that runs from the stator/out of the sprocket case. It was oxidized, cleaning every male/female  to a shine made no difference with recharge ability.
I have a Rick Power Sport 2 in 1 reg/rect. With battery charged at 12.6, when key is on voltage drops .5. When the bike is running the battery runs around 12.2/12.1, when revving the bike it creeps up to 12.7 depending on higher rpm and how long that has been held.
Stator tests good: .2 - .3 ohms 1 and 2 yllw; .3 - .4 1 and 3 yllw, .3 - .4 2 and 3 yllw
The AC output is poor (I'm testing by going yllw to yllw just like resistance test): 10.24 AC Volt 1 and 2, 10.12 AC Volt 1 and 3, I didn't record 2 and 3 but it was around 10;The reg/rect White wire when connected and bike is running is 10.10 V, Black is 10.34
Green from elec. connector off stator to frame ground is 0 ohm
.5 ohm Black Reg. Wire to (-) battery when (-) of battery terminal is disconnected
When I test ground on Green at the reg/rect, I am getting a very small milli volt reading.

I suspect that either I have a shorted ground, or the reg./rect is bad. But I am beside myself with this. I looked up a diode/reverse diode test online and found that the reg/rect was good. But I think I must have done it wrong.

Update: I just tried jumping 12v from the pos terminal of the battery to the white stator wire to have the stator provide full output. No change occured with recharge.
Some posts I've read:
http://forums.sohc4.net/index.php?topic=190205.0   ---> TwoTired's comments about the white wire receiving less than 12 v when the battery is over 12v seems most applicable. So perhaps my reg/rect has the field coil off?
http://forums.sohc4.net/index.php?topic=54044.0
http://forums.sohc4.net/index.php/topic,1012.0.html --> Harry's post I followed for the most part
http://forums.sohc4.net/index.php?topic=155750.0 ---> Scottly's post about the need for a ground led me to try to run a third wire off the green to green connectors from stator to reg/rect to the neg. batt. terminal. No difference was made.
http://forums.sohc4.net/index.php?topic=170150.0

[scottly]

Is this a stock wiring harness? Disconnect the white regulator wire and measure the resistance from the wire to battery -.

[YoungBlood]

It's a stock wiring harness

1.8 ohm from white to neg. batt. terminal, and 1.8 ohm to frame ground.

[scottly]

Somethings not right. What bike is this?

[YoungBlood]

1975 Honda Cb750F

I agree, what's most strange is everything was fine before two weeks ago! In my hunting, I found that the harness had been spliced into. Two wires were live and just dangling (a black wire circuit that splits into the rectifier)... but I am certain it's a stock harness. I can post pictures tomorrow of it w/ the tank removed.

The rear left bulb is out, and the neutral light does not work. Not sure if those bulbs need to be good for their circuits to be closed or not.

[scottly]

1975 Honda Cb750F

I agree, what's most strange is everything was fine before two weeks ago!

What happened two weeks ago??
When you measure the resistance of the white harness wire, disconnected from the regulator, to ground/battery-, it should read about 7 ohms on a 750. This is the field coil, which is an electromagnet that magnetizes the rotor. The regulator varies the current through the field to limit the maximum voltage.
A quick and easy test on a 750 is to check the magnetism of the three screws in the center of the alternator cover. With the key on, there should be a fair amount of strength. If the field is not magnetized, the charging system won't work.     

[YoungBlood]

4 weeks ago the bike took a spill on a right hand turn. No engine damage, but the battery hit against the seat and grounded out. The 15A fuse blew. I didn’t know about the battery at first so I started swapping fuses in a hurry, fuse after fuse blew.

About three weeks ago I snapped one of the Allen head bolts that secure the field coil. I noticed some oil leaking out and quickly applied too much monkey force. I decided to leave what remains of the other 3/4’s of the screw in there because the oil leak stopped (kinda funny?)

Now the battery died for the first time about 3.25 weeks ago. I got it recharged, took it on a 240 mile trip. No issues. Randomly a few days after my couple day trip, battery died again.

I got no #$%*ing clue what’s up. When I get home I’ll double check the resistance on the field coil, thanks for the electromagnetism explanation. Reminds me of when my dad explained how generators produce electricity. I’ll also check for magnetic pull.

[YoungBlood]

I don’t know if these splices are from the factory in ‘75, but also here’s an example of a lone wire I found, live too.

[YoungBlood]

2.7 Ohms resistance, barely any magnetic pull when it is connected to the regulator and the key is on. It cannot hold up a small picture frame nail.

I've got a spare field coil, I'm going to swap it out

[YoungBlood]

Scotty you were right, bad field coil. New one has 7 ohm. Running the bike now: key off 12.66v
At idle: 12.53
At 2k rev: it starts at 13V and climbs, all the way up to 15

My guess now is that this regulator isn’t regulating. So the 2 in 1 is shot, and maybe is the culprit behind the field coil too??!

[BomberMann650]

The reg rec is probably fine - would look at the wires connected to it.  Maybe its not gstting a clear signal the battery has received sufficient voltage.

[YoungBlood]

Bomberman, what wire would do the signaling that the battery is sufficiently charged, black?

[TwoTired]

The stock regulator senses battery voltage by measuring the potential between its black and green wires.  If either path back to battery becomes resistive, a reading error occurs.  So measure voltage loss from batt neg to vreg green AND batt pos to vreg black.  Conditions are with key switch and all lighting on.  When these two readings are added together, you now know the error the vreg “sees”, which is basis for how it can protect the battery from overcharge.
As long as the vreg “thinks” the battery is low, it will tell the alternator to increase the output voltage whenever it is revved enough to produce more power than the bike uses.

[YoungBlood]

Thanks for the thorough explanation 2Tired.

Just to make sure I’m following, if there is a difference between both readings once added, this error “tells” the vreg to limit the volt output? But if there is no difference between these two readings, or a minimal difference then it will not limit the volt output the rotor has provided?

When I get home from work I’ll check these readings and report back. If there is no error reading, what should I next be looking for? A break in the circuit or heavy resistance at some component/section of wire?
Last question: (electric 101) would burnt out bulbs on either circuit line cause resistance in the circuit line by not completing said circuit?

[BomberMann650]

You'll be looking for either wire to have an abnormally high ohms reading

Normal for a plain wire is close to none.

[TwoTired]

Just to make sure I’m following, if there is a difference between both readings once added, this error “tells” the vreg to limit the volt output? But if there is no difference between these two readings, or a minimal difference then it will not limit the volt output the rotor has provided?

Not sure of what you are saying.

A volt meter displays potential between its probe tips.  If you put them on battery POS and NEG terminal, it reports the voltage potential of the battery.  This is true for wherever you place the probe tips.  What you need to find out is if the bike's wiring is accurately distributing the battery voltage to the vreg so it can do its job properly.  Any resistance in a dc pathway will consume and drop voltage across that resistance, be it wire, switch contact, fuse clip, or connector.  The measurements I identified, when summed, tells you the error voltage between battery actual and vreg terminal sense points.  For example: if green path battery to vreg measures .5 V and black wire path battery to vreg measures 1.5v, it would mean the vreg thinks the battery voltage is 2 volts lower than actual, and will supply power to raise that voltage.  So, your 15v reading would be the vreg trying to get the battery up above 13V.  Thats' the math by which all of electricity is defined by.  Don't try to avoid it, or you will never understand electricity.

When I get home from work I’ll check these readings and report back. If there is no error reading, what should I next be looking for? A break in the circuit or heavy resistance at some component/section of wire?
Last question: (electric 101) would burnt out bulbs on either circuit line cause resistance in the circuit line by not completing said circuit?

There will be an error reading.  You need to determine how much of an error is there.  Error of 0.5V total is workable, if not ideal.  More than that, then a switch, or multiple contacts would be suspect.

All the bulbs in the SOHC4 are wired in parallel to the voltage source. They draw power/current independent of other system loads, provided the supply buss ( the black wire distribution lines) have near zero resistance in that pathway.
Burnt out bulbs remove load from the black wire distribution.  This load is current draw.  As current increases to draw power through any resistance, more voltage is dropped passing through that resistive device.

BTW, all devices need two connections back to battery in order to function.  So, don't ignore a solid "ground" or return path for proper function.  That means the green wires.  Some connect to frame.  But, they only work if the battery is also solidly connected to frame, hopefully at the same connection point as the green wire distribution.

[YoungBlood]

Thanks 2Tired, after reading your explanation I do feel I understand more of the basics behind DC power distribution.

I found that the Black wire path is the culprit, with about 1.1V voltage loss. The Green wire path was about .3V volt loss.

I looked at the wiring diagram for the Black circuit and then tested the resistance of each switch and connector on that circuit. I believe from the regulator/rectifier (stock) the black wire first runs to the rear brake switch, then key ignition switch "run", to the front brake switch. Lately I have been too tired after work to mess with the bike, but I did see that I have .2 ohm resistance running from the rect./reg. to the front brake switch. Plus, there is some oxidation on the switch and the female connector. I did not get any ohm readings from the rect./reg. to the rear brake switch or key switch. Tomorrow I will do a  thorough cleaning of all connections/switches on the black circuit and report back.

I will also take a look at those grounds. I know of only two grounds, the frame ground that the battery's negative runs straight to, and a green ground by the ignition coil mounts. Are there any others I should check out?

Thanks again everyone, especially the thorough explanations. I spoke with a sparky at work today about DC, it is slowly making a bit of sense.

[HondaMan]

Thanks 2Tired, after reading your explanation I do feel I understand more of the basics behind DC power distribution.

I found that the Black wire path is the culprit, with about 1.1V voltage loss. The Green wire path was about .3V volt loss.

I looked at the wiring diagram for the Black circuit and then tested the resistance of each switch and connector on that circuit. I believe from the regulator/rectifier (stock) the black wire first runs to the rear brake switch, then key ignition switch "run", to the front brake switch. Lately I have been too tired after work to mess with the bike, but I did see that I have .2 ohm resistance running from the rect./reg. to the front brake switch. Plus, there is some oxidation on the switch and the female connector. I did not get any ohm readings from the rect./reg. to the rear brake switch or key switch. Tomorrow I will do a  thorough cleaning of all connections/switches on the black circuit and report back.

I will also take a look at those grounds. I know of only two grounds, the frame ground that the battery's negative runs straight to, and a green ground by the ignition coil mounts. Are there any others I should check out?

Thanks again everyone, especially the thorough explanations. I spoke with a sparky at work today about DC, it is slowly making a bit of sense.

Yeah, TwoTired is really good at this!
The connectors are often the culprit in these bikes, because their [now old] zinc plating is coming loose from the metal. This makes each junction a small resistor, and it adds up to rob the bike(s) of a lot of the [already-small] alternator output. If you have the option, I might suggest a new wiring harness, like those sold at PartsNmore.com, as a good way to simplify the overall upgrade. They will have all new connectors, and no oxidized junctions in the body of the harness. Just a thought...

Barring that, others here have gone thru their entire harness, cleaning each connector (use steel wool or Scotchbrite) and reassembling. This works, too, if tedious (or a good winter project?). I might suggest a drop of LPS-1 on each one (not LPS-2 or the others) on each connector, which will bar further oxidation. I did mine this way in the 1990s one fine winter's day, and while it much improved the battery charge, the wire jackets are finally beginning to split (from age) and I'll be replacing the harness soon.