Topic: CB400f voltage loss between battery and pretty much everything?

[scottly]

Tenn, you did not measure it right. The idea is to detect where in the neg path that resistance is, that causes the Vdrop you have measured in the 4th step of your V-4 measurement, you have reported us. Have another look at my explanation in reply#3. BTW, the coils have nothing to do with it. Your lights are dim, so there's either a resistance in the pos path to or in the neg path from that light, a resistance that 'eats' volts so to speak. The 4th step was to check the neg path. It is there you found a considerable Vdrop, provided you have informed us correctly. Now you have to detect where in the neg path that resistance is, that causes that Vdrop. First suspect is where that green wire contacts the frame because it happens to be part of the neg path for the volts to travel from both the headlamp and blinkers via the frame to the Batt minus, so there's a good chance the problem is right there. Have a look at the pic Ozzybud has posted. That connection does not look particularly good, does it. It looks corroded. Yours is maybe as bad as Ozzybud's. Put IGN key in ON and the headlight or a blinker ON and then one probe on that green wire and the other on the Batt minus. Report what voltage you read. Ideally it should be zero. But I expect you will read a couple of volts which indicates not all volts make it to the Batt minus, because of a resistance where that green wire connects to the frame, probably caused by rust.

Ok, testing this way I get just 0.010V, which doesn't seem to indicate a problem with that ground wire?

I think I will get the new fuse block before testing further, but what would be a way to check on the right-hand switch, if the headlight power runs through it?

According to your initial reportng the results of your V4-measurement, the Vdrop is somewhere in the NEG path. But maybe your test and/or your reporting has been incorrect. BTW, that's why in reply #69 I added in a subordinate clause: provided you have informed us correctly .

Excuse me, I got lost as soon as you started claiming a voltage drop on the positive side of the circuit was due to a problem in the negative/ground side of the circuit?? Just what is this V4 measurement?

[scottly]

Head (7A) rear connection: 3.48v
Head (7A) front connection: 3.44v

You may have other problems with the headlight, besides the fuse box. The feed for the headlight goes through the starter switch. When at rest, The black wire is connected to the headlight black/red wire. When the start button is pressed, the black wire is switched to the red/yellow(?) wire to operate the starter.

[scottly]

Now you need to find where the 1.85V drop on the red wire is coming from. The red wire goes back from the ignition switch to the main 15 amp fuse, and then from the fuse to the battery + connection, which is usually on the large bolt on the starter solenoid. Once again, the most likely suspect is the fuse box.

[Deltarider]

Excuse me, I got lost as soon as you started claiming a voltage drop on the positive side of the circuit was due to a problem in the negative/ground side of the circuit?? Just what is this V4 measurement?

Scottly, the V4-measurement procedure is in reply#3. Every automotive mechanic here is supposed to have learned this and where needed practise it. Either Tenn has made an error in practising this simple method, or in reporting the results to us. Looking at the results as he communicated them in reply #21, I cannot but conclude the resistance is somewhere in the negative path.

[Tenn_CB400f]

Hi Guys,

I have a new blade type fuse block on the way, and will repeat ALL the V4 tests once it is installed, and make sure to follow the instructions Deltarider provided exactly in case I goofed earlier.

Thanks again!

[Tenn_CB400f]

Excuse me, I got lost as soon as you started claiming a voltage drop on the positive side of the circuit was due to a problem in the negative/ground side of the circuit?? Just what is this V4 measurement?

Scottly, the V4-measurement procedure is in reply#3. Every automotive mechanic here is supposed to have learned this and where needed practise it. Either Tenn has made an error in practising this simple method, or in reporting the results to us. Looking at the results as he communicated them in reply #21, I cannot but conclude the resistance is somewhere in the negative path.

Ok, new blade type fuse block installed. I must have done something wrong on my first V4 test, and trying again, I don't quite get the difference between V2 and V3, specifically for the headlamp.

I also noticed by accident that when the high beam is on, the lo beam gets about 4v, and when the low beam is on, the high beam gets similar?

[bryanj]

That indicates a bad dip switch to me

[scottly]

I also noticed by accident that when the high beam is on, the lo beam gets about 4v, and when the low beam is on, the high beam gets similar?

Is the headlight still dim? I think you mentioned that it had always been dimmer than normal? Exactly how did you measure the voltage; was it with one meter lead connected to the battery - terminal and the other meter lead probing the white and blue wires at the back of the headlight?

[Tenn_CB400f]

I also noticed by accident that when the high beam is on, the lo beam gets about 4v, and when the low beam is on, the high beam gets similar?

Is the headlight still dim? I think you mentioned that it had always been dimmer than normal? Exactly how did you measure the voltage; was it with one meter lead connected to the battery - terminal and the other meter lead probing the white and blue wires at the back of the headlight?

Ignition switch on, lo-beam on. Red probe on the + battery terminal, black probe on the "main" connector in the headlight plug = 12.1v.

Ignition switch on, lo-beam on. Red probe on the + battery terminal, black probe on the "pass" connector in the headlight plug = 4.0v.

Ignition switch on, hi-beam on. Red probe on the + battery terminal, black probe on the "pass" connector in the headlight plug = 12.1v.

Ignition switch on, hi-beam on. Red probe on the + battery terminal, black probe on the "main" connector in the headlight plug = 3.95v.

Headlight maybe is less dim but still not really bright.

So the fusebox swap seems to have done something.

[scottly]

I'm not following you. What do you mean by "main" and "pass" connectors?? Is the plug on the headlight the stock one, with a white, a blue, and a green wire?
Edit: You still have a 4V drop in the positive side of the feed to the headlight, like you measured before at the headlight fuse.
The dimmer switch has three wires: blue, white, and red/yellow(?). The red/yellow is the supply into the switch, and the blue and white are the hi and low outputs from the switch. Measure the voltage on the red/yellow wire the same way, from battery + with the key on.

[Tenn_CB400f]

I'm not following you. What do you mean by "main" and "pass" connectors?? Is the plug on the headlight the stock one, with a white, a blue, and a green wire?
Edit: You still have a 4V drop in the positive side of the feed to the headlight, like you measured before at the headlight fuse.

Correct on the wire colors. The plug that connects to the headlight has three wires, and the plug is marked Ground, Main actually "Drive" (lo-beam) and Pass (hi-beam).

[scottly]

Gotcha. Read my last edit...

[scottly]

Head (7A) rear connection: 3.48v
Head (7A) front connection: 3.44v

You may have other problems with the headlight, besides the fuse box. The feed for the headlight goes through the starter switch. When at rest, The black wire is connected to the headlight black/red wire. When the start button is pressed, the black wire is switched to the red/yellow(?) wire to operate the starter.

[Tenn_CB400f]

I'm not following you. What do you mean by "main" and "pass" connectors?? Is the plug on the headlight the stock one, with a white, a blue, and a green wire?
Edit: You still have a 4V drop in the positive side of the feed to the headlight, like you measured before at the headlight fuse.
The dimmer switch has three wires: blue, white, and red/yellow(?). The red/yellow is the supply into the switch, and the blue and white are the hi and low outputs from the switch. Measure the voltage on the red/yellow wire the same way, from battery + with the key on.

Ok thank you! I see a blue and a white, but no red/yellow. There's a Black/Yellow that the diagram says goes to "HL". With hi beam on, I get 3.1v and with lo-beam on, I get 3.0v.  With the key off, I get battery voltage (~12.75v).

Both the blue and the white alternate between 12.1v and ~3.3v depending on the way the dip switch is set. White is 12.1v with high beam on, and 3.3v with lo beam on, and Blue is 12.1v with lo beam on, and 3.3v with high beam on.

There are also an orange and an orange/white wire coming off that switch. The diagram says Orange goes to "L" and the Orange/White goes to "PR" on the switch. The Orange shows 11.95v and the O/W 3.3v.

Clear as mud, right! 

Thank you for all the help!

[scottly]

The orange is left turn, and the orange/white is the running light.
Since you measured a large voltage drop on both sides of the headlight fuse two weeks ago, it means the drop is happening before it ever gets to the dimmer switch, pointing back to the starter switch.

[Tenn_CB400f]

The orange is left turn, and the orange/white is the running light.
Since you measured a large voltage drop on both sides of the headlight fuse two weeks ago, it means the drop is happening before it ever gets to the dimmer switch, pointing back to the starter switch.

Checking the wires coming off the start/kill switch, I see 12.4v at the yellow/red, and just 2.3v at the black/red with the start button NOT pressed.

[bryanj]

Should be 12 volt on yell/red with button PUSHED 12v at black/red with button NOT PUSHED

[scottly]

The orange is left turn, and the orange/white is the running light.
Since you measured a large voltage drop on both sides of the headlight fuse two weeks ago, it means the drop is happening before it ever gets to the dimmer switch, pointing back to the starter switch.

Checking the wires coming off the start/kill switch, I see 12.4v at the yellow/red, and just 2.3v at the black/red with the start button NOT pressed.

What do you get on the solid black wire, which is the power input to the switch.

[scottly]

Should be 12 volt on yell/red with button PUSHED 12v at black/red with button NOT PUSHED

Bryan, we are measuring the voltage drop directly, not the actual voltage.

[bryanj]

Thats not the way i read the reported readings

[Tenn_CB400f]

I'll check the black wire.

And this is just checking voltage. Red probe on the + battery terminal, black probe on the bullet connector of the wire in question.

I got fouled up in that V4 testing and couldn't quite understand a difference in V2 and V3.

[Tenn_CB400f]

Black wire from start/kill shows only 1.3v with the key on

[scottly]

That means you are dropping 1V through the switch itself. Have you measured the drop at the red and black wires at the ignition switch since you replaced the fuse box?

[Tenn_CB400f]

Will do so, thank you.

Does the fact that the low-beam wire is seeing ~4v when the high beam is on, and the high-beam wire is seeing ~4v with lo beam on indicate a problem with the dimmer switch itself?

[Tenn_CB400f]

Excuse me, I got lost as soon as you started claiming a voltage drop on the positive side of the circuit was due to a problem in the negative/ground side of the circuit?? Just what is this V4 measurement?

Scottly, the V4-measurement procedure is in reply#3. Every automotive mechanic here is supposed to have learned this and where needed practise it. Either Tenn has made an error in practising this simple method, or in reporting the results to us. Looking at the results as he communicated them in reply #21, I cannot but conclude the resistance is somewhere in the negative path.

V4 test revisited, following the new fuseblock, and I have explained exactly WHAT I measured and probably still did it wrong.

Low beam:

V1 (measured across battery terminals, key on, lo beam on): 12.49v
V2 (measured across the "drive" (low beam) and ground connectors on the headlight socket): -0.002v (doesn't make sense!)
V3 (measured across the + battery terminal and the "drive" connector on the HL socket): 12.18V
V4 (measured across the - battery terminal and the ground wire on the HL socket): 0.192v


High beam:

V1 (measured across battery terminals, key on, high beam on): 12.40v
V2 (measured across the "pass" (high beam) and ground connectors on the headlight socket): -0.03v (doesn't make sense!)
V3 (measured across the + battery terminal and the "pass" connector on the HL socket): 12.11V
V4 (measured across the - battery terminal and the ground wire on the HL socket): 0.222v

ugh

I also re-checked the green ground wire just behind the airbox against the battery minus, key and HL on, and get 0.010v.