Topic: Having trouble with my '75 CB400F - Battery constantly discharging

[scottly]

I also tested the main fuse and I would say it's hot. The meter shows 0.8 across it.

There's your sign.

[jakec]

I already cleaned the clips for all of the fuses, what else should I do? Sorry I reread Bodi's post but I didn't see anything other than cleaning those clamps.

[scottly]

Check the solder joints on the back side of the fuse block, and look for melting of the plastic around the clips. You've located a 0.8 V drop at the fuse, so you know where to concentrate. Might be time to upgrade to a blade type fuseholder?

[jakec]

Just to clarify I had the positive lead on the left side of the fuse, ground on the right. It showed 0.8 volts. What does this indicate? A loss of 0.8 volts from the time the power enters the fuse to the point it leaves? I just want to understand. I will check on the fuse block again although I had it off the bike to clean the clamps and everything looked good!

[scottly]

What does this indicate? A loss of 0.8 volts from the time the power enters the fuse to the point it leaves?

Correct. The heating of the fuse also indicates a poor connection between the clips and the fuse. Once overheated, the clips can lose the tension clamping them down on the fuse ends. How easy is it to remove the main fuse, compared to the 5 amp taillight fuse, just for a point of reference?

[jakec]

All of the fuses were equally hard to remove, the clamps were pretty tight. The contacts all looked clean as well, but I hit them with some sandpaper just in case (this was before the main fuse tested 0.. All the other fuses tested 0.0

[jakec]

We took a look at the fuses last night and the main 15a fuse looks like the filament has some kind of corrosion on it. So we will be trying new fuses tonight.

[mkngt]

We took a look at the fuses last night and the main 15a fuse looks like the filament has some kind of corrosion on it. So we will be trying new fuses tonight.

Hey guys, back from the dead. Appreciate all the info here, truly.

So the latest update is when I put in new fuses (engine off), i was getting a read of 2/100V (old fuse was 6/100V).

I plugged everything back in again, turned on the engine (waited for it to heat up), then rev'd it hard while watching the battery. It rose up to 15.10V before I stopped @7k rpm. Any thoughts?

[scottly]

Measure the voltage at the black regulator terminal as follows:
Connect one meter lead to the positive battery terminal, and the other meter lead to the black regulator terminal, and turn the key on, without starting the motor; this will measure the voltage drop through the wiring harness, fuse box, and ignition switch. This should be less than 1 volt.

Do this test again.

[jakec]

That test gave the same reading, 0.02V.

[scottly]

That test gave the same reading, 0.02V.

That's not possible; you didn't do the test as described. BTW, did you "turn up the regulator" per the Mike Nixon blog?

[jakec]

He didn't make any adjustment to the reg.

We tested the red lead on battery, black on regulator prong (unplugged) and got 0.02.

We tested red on battery, black on regulator lead (unplugged) and got 10.6.

Do you mean to test with the regulator hooked up?

[TwoTired]

Functional tests are always done with the parts installed and active.  Some things behave differently when under the stress of operation.

But, your measurements are fine so long as the bike sits in the museum. 

Cheers,

P.S.  You are trying to find out if your regulator is getting actual true voltage report of the battery.   Lie to the regulator and it can't do it's job properly.

[jakec]

Yes the key was on for the tests that we did. With the old fuse it showed 0.06. With the new fuse 0.02.

[scottly]

Measure the voltage at the black regulator terminal as follows:
Connect one meter lead to the positive battery terminal, and the other meter lead to the black regulator terminal, and turn the key on, without starting the motor; this will measure the voltage drop through the wiring harness, fuse box, and ignition switch. This should be less than 1 volt.

Do this test again.

This test is done with the black wire connected to the regulator.