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I am getting to the end of my 1975 R90/6 project.

The bike was an eBay find, and though the wiring harness is generally sound it does have some issues.

Currently with the ignition switch in the off position, I have a current drain of some 2.5 volts, originally the drain was a full 12.75 volts, but after I removed a pair of retro fitted spade fuses and put back the originals, the drain went back to 2.5 volts. The ignition switch is new.

What method do I use to trouble shoot the wiring to find the drain? Are there any places where it inmost likely to be found? I think that rob did a write up on the issue, but it was in one of the previous forums.

None of the indicators are working and the parking light is on all the time I don't know if this is related to the current drain issue.

There is also a problem with the starter relay, when I press the starter button I get a click, however the current produced in the black wire that goes to the solenoid is all of .6 of a volt. I assume that this is not enough to trigger the solenoid/starter , which works fine when hot-wired.
Thanks in anticipation...

Charles, can you first elaborate how you get to your numbers? 2.5V is not a current drain that would be a measurement in A(mpere). It seems to indicate you're talking about a voltage drop down to 2.5V from an additional 12.75, measured at the battery poles?

If you know absolutely nothing about this bike, I would

1. measure voltage across the battery poles w/ ignition off
2. turn ignition on
3. measure again across the battery poles
4. If you experience a voltage drop, disconnect one connector of the wiring loom after the other and measure the battery voltage inbetween disconnections until you find the circuit that causes trouble.

If you know nothing about electricity, call a friend (your cavalier usage of the term voltage drain and associating it with a voltage value implies you don't). Maybe Rob lives round the corner, he'll be a great resource. I am just a really bad teacher.

Alternatively, call a Tech Day and invite plenty Airheads! Your problem will be fixed in no time.

In line with what Stephen said, chasbmw, I too wasn't able to understand what you were trying to say. There are people who can probably help you, if they can figure out the problem.

Might I suggest another approach to help us understand. It will mean quite a bit of detail, but as it stands now we have no common language. My thought would be for you to tell us step-by-individual-step, the function you're measuring with your meter (volts, ohms, amps), where your probes are connected, the reading you seeing, an action you then take, and what the new reading you're seeing.

For example, again following Stephen, you would tell us something like.

Meter set to DC volts.
Red lead touching positive battery post.
Black lead touching negative battery post.
Ignition switch off.
Reading 12.7 volts.

Now turned ignition switch to "on"
Reading 10.2 volts

Now that's almost certainly not what you're actually doing and seeing, but that's not the point. We would be communicating what you're doing and what you're seeing, and that is the point.

Not trying to pile on you. Trying to help you.

If Stephen or I were there alongside you, there would be no need for the tedious reporting. But we aren't and you need help.

And if Stephen or I aren't around there are a lot of others here who can give you good advice.


Ken

Stephen, Ken,

The multimeter is set to volts on the 20v range.

What I have done is to put voltmeter between negative pole of battery and earth.

With the ignition switch turned off I get the 2.75 volts and with the ignition on 12.75 volts.

So to find out where the current drain is I should leave the voltmeter where it is and disconnect wires on the circuit board to see when the voltage drops to zero?

Does this help? Yes I am an at Ignoramus in terms of electricity. Rob is in hospital at the moment and I want to get this bike running as I want to ride it to Greece in a couple of weeks!

Charles

chasbmw wrote:Stephen, Ken,

The multimeter is set to volts on the 20v range.

What I have done is to put voltmeter between negative pole of battery and earth.

With the ignition switch turned off I get the 2.75 volts and with the ignition on 12.75 volts.

So to find out where the current drain is I should leave the voltmeter where it is and disconnect wires on the circuit board to see when the voltage drops to zero?

Does this help? Yes I am an at Ignoramus in terms of electricity. Rob is in hospital at the moment and I want to get this bike running as I want to ride it to Greece in a couple of weeks!

Charles

Interesting. In troubleshooting I've never come across a need to measure between the negative post of a battery and a chassis. Why are you making that measurement? What are you trying to find out or explore? What is the bike doing wrong or not doing right?

The reason I'm confused is on a well grounded battery there will be no voltage difference between the negative post and chassis ground. That's what the big cable if for, to strap, in effect, the battery post to ground. And with a good connection I don't see how any significant voltage drop can exist. And whether the ignition switch is on or off shouldn't make a difference.

The only thing I can say now would be to take the negative battery cable off and carefully inspect the two ends, especially the one at the battery post. Sometimes, particularly near the terminal, corrosion can exist hidden under the jacket of the cable. If you really want to go down this path I would suggest taking a set of car jump cables and connect between the battery post and chassis ground.

But the above doesn't sound like a profitable line of inquiry to me. What is it you're trying to do. What's not working right?

The voltage drop between the battery negative post and ground has come up before on the forum. But I don't remember anything useful coming out of the discussion(s). With a well grounded battery the resistance is so low that it would be hard to detect any difference at all.


Ken

chasbmw wrote:Stephen, Ken,

The multimeter is set to volts on the 20v range.

What I have done is to put voltmeter between negative pole of battery and earth.

With the ignition switch turned off I get the 2.75 volts and with the ignition on 12.75 volts.

So to find out where the current drain is I should leave the voltmeter where it is and disconnect wires on the circuit board to see when the voltage drops to zero?

Does this help? Yes I am an at Ignoramus in terms of electricity. Rob is in hospital at the moment and I want to get this bike running as I want to ride it to Greece in a couple of weeks!

Charles

Hmmm,

A strange test but it might tell us something...

Is this with the battery ground wire connected?

If it is, then I would say that the ground wire has failed completely. You should not get any appreciable voltage difference between the negative battery terminal and ground (say .5 volts at most).

If you are getting these readings with the battery negative lead disconnected, then I would suggest that you connect it and see what happens. Even if everything seems OK, I'm not convinced that everything is correct... the 2.75 volt reading with the ignition off may indicated that there is a rogue drain current flowing when it shouldn't be. Try this procedure.

1) Disconnect any clock or any other electrical stuff that you would expect to work with the ignition off (an alarm is a prime candidate)

2) Disconnect one of the battery terminals (doesn't matter which, negative is probably easier).

3) Set your multimeter to the highest AMPS range... N.B. on many mulimeters, you may have to put the positive lead in a different hole to get the highest AMP range.

4) Connect the two leads between the battery terminal and the lead you have disconnected from it.

5) You should get no reading from the meter.

6) Repeat useing the next lowest amp reading

7) Any current more than - say - 50 milliamps needs to be investigated

Note1. If your highest AMP range is less than 500 ma do not use it for this test

Note2. Do NOT switch the ignition or the parking lights on with the meter connected in this way. This is purely a test to see if there is any current leakage when everything is switched off. If you do, you will probably damage the meter.

Let us know the results and, if there is still a problem, we'll try to assist.

BTW out of Hospital now and just a little sore so grounded for a few days. No biggy.

Rob

Rob

Thanks will do and report, please ignore email which I sent before reading this.

A little knowledge is a dangerous..............

Using the correct AMP function of the multimeter I found that there was no current drain! I followed Rob's instructions to the letter.

I was checking for current drain because when I last had the bike attached to a battery I had the impression that the battery ran down rather too quickly.

Thanks for your help and patience

Charles

Rob nailed down a great procedure. If you truly have no current drain with everything turned off, then you don't have a path to ground. It ISN"T dischraging via the wiring. Maybe you have a bad battery. That would be my next suspicion.

I will disagree with Rob on one thing. Even a 10-15 milliamp drain is too much.