Topic: HELP! 12v+ at the battery, 10.5v everywhere else!

[yodagruv]

I need the benefit of this forum's expertise and experience.  My '75 CB550K has a good (new) battery offering 12v+ to the electrical system and the alternator is providing more just as it should, however all other places in the electrical system show 10.5v.  It seems that is enough to dimly operate signal markers and moderately operate the headlight but my flashers and horn are inoperable due to this and i suspect the coils are suffering as well.

We jumped a hot lead straight off the positive battery terminal to both the horn and flashers and they function properly under those circumstances, but that's obviously not a feasible solution, so what do you guys think is up?  Voltage Regulator? Rectifier? Something else?

HELP!

[Alan F.]

You may need to clean the connection from the negative battery terminal and the frame, but the simple solution may be adjusting your voltage regulator.  There is a proceedure in the manual.

[yodagruv]

which manual?

[scottly]

Check the fuse holders. Make sure the clips are clean and are gripping the fuses tightly.

[DH]

If all else checks ok like mentioned, check voltage going to and after the ignition switch.

[yodagruv]

You may need to clean the connection from the negative battery terminal and the frame

That's fine, cable looks recent, too.

Check the fuse holders. Make sure the clips are clean and are gripping the fuses tightly.

Fuses and clips are good to go.

make sure there's 12v at the main fuse itself

Is that the 15A fuse on the far right?  The other two are 5A and 7.5A i believe.

May be voltage drop thru the ignition switch.

How would i tell?  We tested for continuity in the ignition switch and it was fine in that regard.  How can i check voltage there?

...the simple solution may be adjusting your voltage regulator.  There is a proceedure in the manual.

i didn't realize you could adjust that, i don't see anything in the owners manual or in the common service manual about adjusting a voltage regulator.

[scottly]

...the simple solution may be adjusting your voltage regulator.  There is a proceedure in the manual.

i didn't realize you could adjust that, i don't see anything in the owners manual or in the common service manual about adjusting a voltage regulator.


[/quote]
Don't adjust the regulator to compensate for a voltage drop in your wiring.

[yodagruv]

Don't adjust the regulator to compensate for a voltage drop in your wiring.

Then how do you correct it?  i would think that's what the regulator would do.  12V in should be 12V out, right?  What am i missing?  Does everything go through the ignition switch first?

[scottly]

 What am i missing?  Does everything go through the ignition switch first?

Yes. Also, any connectors along the way may cause a voltage drop if dirty or corroded.

[IndyFour]

Dirty contacts in the switches (ignition switch, light switches, horn button, etc.) will cause a current drop.  If you can determine where the current drops closest to the battery, then you will likely have the culprit....but then again, it might just be several dirty terminals and switches that are adding up to increased resistance and low voltage at the point of load (i.e. lights, horn, etc.)  If all of the hot leads inside the headlight bucket show low voltage, then I'm betting that it's a bad connection or the ignition switch.  If the leads coming off of the ignition switch (key) are normal voltage, then it's probably dirty switches for the lights, horn, etc.  You have to remove the switch assemblies from the bars and give them a good cleaning and a fresh coat of electric grease.

I had a voltage drop in my headlights resulting in a dim beam.  My solution was to install a relay for both the low and high beams and ran a dedicated hot to the battery with a new fuse.  Lights are now brighter than they probably were new.

I would start by looking in the headlight bucket for loose connections or corrosion and test at various points if you haven't done that yet.

Good luck.

[yodagruv]

Hey, guys i really appreciate all the input so quickly!

We did open up the handle bar controls and clean them, so that's covered.

Every single connection we expected to have 12V on only had 10.5V consistently, no variation except may a couple of hundredths; for instance, Ignition coils, horn, blinkers, all lights, really.  Bought a new winker, just for kicks.

Had the headlight out of the bowl and all the connections we inspected there and, in fact, all over the bike are just peachy, no corrosion, etc. If there's a bad connection it's very, very early in the system.

Which makes me think if the key switch precedes all other connections that may be the most likely and least expensive culprit.  How can i test voltage in and out of it, though, the connectors are all closed off inside the connector.  Bridge them or something?

[DH]

Ignition switch has a 4 wire connector that plugs to another connector half in the main wiring harness. Usually located under the tank. separate the two connector halves and check for corrosion inside. Clean/repair if nec. If ok, jumper the black wire to the red wire, and the brown wire to the brown and white wiire. By doing this, you are bypassing the ignition switch.If that fixes it, get a new ignition switch. Otherwise, refer to other previous suggestions.

[yodagruv]

Perfect.  That should make an "X" across the connector, correct?  If that is not a fix, then check the regulator?

[scottly]

make sure there's 12v at the main fuse itself

Is that the 15A fuse on the far right?  The other two are 5A and 7.5A i believe.

What voltage do you measure at each end of the 15A fuse. (it feeds the ignition switch)

[yodagruv]

What voltage do you measure at each end of the 15A fuse. (it feeds the ignition switch)

Not sure.  Will check again, may be next weekend, though, my father in law is the electrical dude, my meter sucks.  I could do the jumper biz, though, Monday or Tuesday.

[DH]

Perfect.  That should make an "X" across the connector, correct?  If that is not a fix, then check the regulator?

Yes I believe so. If that doesn't fix things, the problem is elsewhere.
As mentioned earlier tho, regulator adjustment is only done when the charging system is not operating properly. Post your results.
If the ign switch is ok, someone with more electrical experience may have something more to add. And re read the previous posts too.
They're good ones.

[yodagruv]

got it.

[scottly]

If you get good readings at the fuse, try unplugging/replugging the ignition switch a few times; may be corrosion on the connectors inside the plug.

[yodagruv]

They were clean.

[scottly]

What voltage do you read at the fuse?

[yodagruv]

What voltage do you measure at each end of the 15A fuse. (it feeds the ignition switch)

Not sure.  Will check again, may be next weekend, though, my father in law is the electrical dude, my meter sucks.  I could do the jumper biz, though, Monday or Tuesday.

[scottly]

If it were me, I would do the simple voltage measurement, before trying to jumper switches. If the fuse has good voltage in and out, then move on to the ignition switch. Being aware that over 90% of electrical problems occur in connectors, I would first suspect the very plug you are talking about jumping. 

[yodagruv]

Yeah, i'll check the voltage at the fuse first. The connectors we inspected, including the key switch, were all clean and good to go.

[scottly]

Keep us posted!

[yodagruv]

right on.

[Spanner 1]

Totally NORMAL IMO without the motor running and revving above say, 2,500 rpm. The battery will deplete quickly with ign. on, headlight on and no charging... flashers first to go after several seconds ! ( normal IMO ).
The older I get ( cranky old fart syndrome ) the more I want to say ' take the dang bike for a ( at least 20 mile ) ride and then see whats not working '.... 

[yodagruv]

Totally NORMAL IMO without the motor running and revving above say, 2,500 rpm. The battery will deplete quickly with ign. on, headlight on and no charging... flashers first to go after several seconds ! ( normal IMO ).
The older I get ( cranky old fart syndrome ) the more I want to say ' take the dang bike for a ( at least 20 mile ) ride and then see whats not working '.... 

Battery and charging system seem fine.  i bypassed the ignition switch by jumping the harness, the exact same condition remains.  Didn't have my meter with me nor time to check any other voltages.  So, where does the power go directly after the switch (i know it could technically be before) but all of the contacts are clean and good that i can see.  there is a lone, stray green wire that doesn't appear to connect to anything.  here's a few photos of the fusebox, etc.  click them, they get bigger! 

[IndyFour]

Did you check the voltage on the hot terminal of the ignition switch harness (i.e. where you bridged/bypassed it)?  If it is under voltage there, it is most certainly further back towards the battery.

That green wire is a ground that is for a three-terminal signal flasher if you had one.  It's not needed if you just have a two terminal type.  My friend's CB500 has the same spare ground wire on his bike.

[TwoTired]

You are chasing a voltage drop situation.
A voltmeter measures the differential between it's measurement probes.  Use this capability to find the voltage drop in the path.

Place one lead on the battery post.  Place the other on the solenoid post.  The reading will be the loss of voltage between those two points.
Note it.
Then move the battery post probe to the solenoid post, and the other probe to the red where attaches to the main fuse.
This will show the voltage lost between those two points.
Then from the fuse output to red at the key switch.
Then measure from the red to black wires.
Then measure between fuse posts (you should polish the contact points bright and shiny, btw, as oxidation can be transparent).

Use the wire diagram to "chase" the pathway losses between battery post and end using device.  You want to eliminate or reduce any pathway serial connection losses.  Finding where the losses are is the first step toward correction.

Cheers,

[yodagruv]

Looking at the color diagram from this website i have a couple of questions:

1a. It appears that the hot lead comes from the battery, splits to the solenoid ("starter magnetic switch?") and then joins to a split to the rectifier and the CENTER fuse, is that correct? 1b. What value is that fuse intended to be?

2a. It then appears to leave the fuse and goes directly to the ignition switch?  2b. Does the top block in the diagram represent the lugs and the lower two represent the "on" position and then the "park light" position?

If i read this right, my voltage drop is most likely prior to the ignition switch since all the voltages at all the connections we tested at 10.5V come after that.  That means it looks like i have 4 connections (like bullet connections?) and one plug connector to check before/to the fuse and then there's just a single run from the fuse to a connector and then down the line to the switch connector.

Am i reading this thing correctly?

BTW, what order do the values go in? Right now left to right i have 5A, 7A, 15A.

[Spanner 1]

With the ignition off there would be no reason for any voltage drop up to where the red wire connects to the ign. switch... but look at the battery connection to the solenoid , that's where the feed for all the bikes electrics are fed from ( red wire to fuse block ).... what's up with all the corrosion?

[scottly]

but look at the battery connection to the solenoid , that's where the feed for all the bikes electrics are fed from ( red wire to fuse block ).... what's up with all the corrosion?

1+ (good eye, Spanner!)

[yodagruv]

...look at the battery connection to the solenoid .... what's up with all the corrosion?

Noted, that's why I took the photo. However, voltage in and out of there seems fine. I had a moment this am and checked the voltage at the switch connector. There appears to be a drop of over 1V at the red wire when the switch is in the "run" position in the center and the voltages on all the other wires are the same in that position but consistent voltage with battery in the first and third switch positions. So it drops going into AND out of the switch when the switch is in the center position.

[scottly]

So it drops going into AND out of the switch when the switch is in the center position.

You have narrowed the voltage drop down to somewhere between the battery and the red wire where it connects to the switch: main fuse, solenoid post, etc. Does your electric starter work??

[yodagruv]

Starter works fine. The main fuse posts are my next check... This afternoon.