Ignition / Starting Issue

[cbclemmens]

A little clarification please. When you say you create a spark at the "points" are you talking about the contact points on the switch, or the breaker points in the ignition system? I think you mean the former and if so, it sounds as though they are not making contact all the time. I would check the voltage with a volt meter at the downstream side with the light on and off. Also, try pulling the ground off the battery and measure the resistance between pins 15 and 30 with the key in. It should be zero. Have you cleaned the contacts with sandpaper (>120 grit)? Sometimes there is oxidation that spray cleaner won't remove. What you are describing is somewhat how a capacitor would behave. You may have oxidation or other foreign material on the contacts making them behave as a capacitor.

Still curious.

Craig

[chrishea]

Have you tried changing the light bulb for the red light?

As far as I know, pushing the key down only closes the contact on the bar.

Another area would be to check the grounding points. A bad ground can cause some odd problems.

[CafePB]

Craig, you are correct I was talking about the contact points in the switch. I did some of the measurements that you suggested.
The voltage at the blue wire of the socket for the red light, the D+ on the relay for the starter and the D+ of the voltage regulator measures:
11.4 V with the key pushed in, but the light not illuminated.
2.4 V with the key pushed in and the light illuminated.

The resistance between 15 and 30 is 0.2 ohm, with the ground removed at the battery.
The points on the switch have been sanded earlier in my troubleshooting efforts.

Chris, I have not changed the bulb, because I do not have a replacement and the bulbs for green and orange have a different size.
However I rigged the bulb up with crocodile clamps to eliminate the socket and any intermitted contact. when I push in the key I have the same malfunction as described. Lifting the contact points once will make the light come on.

I am still at a loss
Thanks for the support.

[chrishea]

Did you jump the ignition switch? 30 to 15 on the circuit board? Same behavior?

Now we just need to figure this out!

[CafePB]

Chris,
yes I did. Same behaviour.

[chrishea]

I poked around this morning and remebered Snowbum discussion /5 starting issues. Sounds like your problem.

Entire article here: https://bmwmotorcycletech.info/slash5cricket.htm

Extract: “The /5 motorcycles have another peculiarity, that is part of the circuitry that is described in the below article, so, a brief mention of it in this paragraph. The transistor inside the /5 starter relay (no other Airhead model after the /5 has a transistor in the starter relay) requires a connection to ground in order to operate. This grounding is done by the circuitry inside the alternator's Voltage Regulator! ...yes, really. If that VR is faulty, the GEN lamp will NOT illuminate with key on, engine off. Of course, the same effect is seen if the alternator ROTOR is open. To eliminate the rotor and prove that the VR is likely OK, simply SHORT D- to Df terminals on the alternator. If the lamp then illuminates, the rotor is likely open-circuited. If not, then you need to do further testing...bad lamp? or?” - from Snowbum.

With that, I think you’ve eliminated the rotor already. Is this an original voltage regulator? If it is, they have fine windings in them, they were electromechanical, not transistorized and those contacts and fine wire windings fail over time. There are many sources of Airhead transistorized regulators.

[CafePB]

Thanks for digging deeper.
I replaced the voltage regulator after I had read Snowbum's article at the beginning of my troubleshooting venture. Unfortunately that did not help. All the tests and replies that I show above are with that new regulator installed.

I just can not find anything that could cause the intermittent / delayed illumination of the charging light.
Not sure what else I can do.

[cbclemmens]

I agree with Chris. It sounds like a bad starter relay. I think euromotoelectronics.com sells an upgraded version.

Craig

[CafePB]

I have replaced the Starter Relay SR 7570 with an upgraded one from EME.
The Voltage Regulator had been replaced with a unit from EME before I bought the bike.
Do you think one of them could be bad?

@ Chris - I meant to write above that I replaced the relay , not the VR
All tests up to now have been done with the replaced regulator and relay.

While I was working on the bike the other day I actuated the starter button and also the blinker switch. After that the red light does not come on as predictable as before. For a while now it came on if I separated the contact points in the ignition switch once or twice. Now it sometimes takes a dozen tries before the light comes on again.
Could the switch on the handlebar cause any interruption for the red light?

Thanks
Peter

[chrishea]

Well. Since the VR and starter relay are changed, those should be eliminated.

Looking at the wiring, the horn and the charging system are powered off the same fuse. Since the horn switch is on that circuit, there could be something there. Or disconnect the ground for the horn and see if that changes something. (grasping here…)

From the red light, it goes down to starter relay, diode board, voltage regulator, then the brushes, then back to the voltage regulator to ground. Are the brushes long enough and making good contact with the rotor? Good ground at the voltage regulator?