Electrical Mystery for a Sherlock Ohms

[ElevenFifty]

BIKE

04 RT runs like a top, start good, BMW original battery. Put the bike on BMW charger - green lights, fully charged. No symptoms of any electrical problems

 

AUDIO SYSTEM

Starcom1 with iPod. I have two of these units for the RT and a Honda - identical model starcoms both work normally.

 

SYMTOMS

A week ago, I noticed that whenever I accelerated to 4K the audio would cut out. Throttle up, sound off...throttle down, sound on. I've used the Starcoms for 6 months+ and never had this symptom before. Both Starcoms do the same thing - identical behavior. I put a full charge on the battery, reran the wiring and tested again . . .now the magic spot is right at 5K. I can turn the system on and off with the throttle!

 

OTHER INFO

VOX is off . . . tested with mic sensitivity all the way down ... doesn't matter whether the shield or my visor is up or down.

 

TESTS:

Hooked up an analog VOM to the power plug for the Starcom and couldn't see any voltage drop when simulating the situation (but it's an inexpensive VOM and I can't watch it closely and ride safe). Only happens on the road when the bike is under load (THIS IS THE KEY SYMPTOM) - sitting in the driveway the music just plays on and on.

 

Is this an early sign of a charging problem? What say you Watson - the games afoot!

[bmwmick]

David,

Do you have an isolator on the audio line from the ipod thing to the STarcom? I assume the ipod is powered from the bike, if not, Nevermind.

To eliminate the alternator, you could remove the D+ wire from the back of the alternator. No field voltage and you would get 0 volts out of the alternator. Would make for a quick test.

 

Mick (with a correctly operating STarcom1)

[ElevenFifty]

Thanks Mick -

 

iPod is running off it's internal battery.

 

It appears that the system is cutting out due to a voltage drop when the bike is accelerating under load. The 'cut-out' is always at the same place in the rpm range. Once the sound shuts off, it will stay off as long as I'm accelerating - As soon as I back off the throttle, the sound comes on again. What could be causing the voltage to drop?

[MotoMoose]

You didn't say what circuit you wired your StarCom to. Have you tried to find another power source for it, ie. circuit? Also make sure your ground is as pure/ close to batt- as possible, same for power too. Does your meter have a record function, if it does, you should be able to see min/max readings after your 5k RPM blast. This may give you the data you were looking for about voltage drops. Give us some more info. and we'll eventually track it down.

[ElevenFifty]

It's wired into the tail light circuit. In line noise filter - works fine. Symptom is there whether the filter in in-line or not. I'll try grounding at the battery.

 

My intuition is that something else has changed and is pulling the voltage down on acceleration - I don't have a recording meter so I'm just guessing here.

[Ken H.]

Well this is indeed a puzzler...

 

Does it do this when accelerating through 5K and/or when holding at a steady 5K RPM?

 

If you accelerate through 5K on to say 7K, does it come back on at the higher RPM?

 

Does other loads such as lights, heated grips, anything else you can turn on or off move the RPM point where this is happening?

 

Right now my head is somewhere around an alt. belt that is slipping under a certain specific set of circumstances. Or possibly a voltage regulator (internal to the alternator) issue. But I'm not at all sure yet.

 

Ignition noise ingress seems like a possiblity too.

 

If you use a different source of audio other than the iPOD, do you get the same effect?

[Edgar]

You didn’t state which iPod that you are using, and where you mount it. If it’s not a Nano or flash drive based unit could the vibration be causing the iPod to stop playing? Try a small portable radio or portable CD player to see if it still happens.

Another thought is that you may have a loose or flaky headset to Starcom1 connection that disengages under acceleration. The Starcom1 does not power up if it does not have that connection. The vibration under acceleration could contribute to this. I have had mine cut out while riding when the plug mysteriously disconnects.

To rule out bike power (If it's not a Starcom1 Advanced) try the same test using "AA" batteries

[ElevenFifty]

It's a nano - also does cuts out with radio - haven't ridden two up since it started so I don't know if the whole unit is cutting out or just the audio channel - I'll try my wife's helmet and see if the problem is in the helmet cabling. Remember I changed two identical Strarcoms and got the same result -

 

In common: - bike electronics, helmet cable, remote volume

Tested/eliminated: Starcom1 (I get the same results on both), background noise, vox

Main Symptom: cuts out Only under load and during acceleration

Curious effect: after a FULL charge on the battery, the point where it cuts out went from ~4K to ~5K

 

I'll do some more tests.

[ElevenFifty]

Isolated from vibration - no change

Disconnected ALL remote lines e.g. Push to talk, remote volume - no change

Run with high beams and fog lights - no change

 

There is an electrical DEMAND at around 4K under acceleration that is enough to shut down the Starcom . . . this is a problem that has arisen in the last two weeks or so . . . Anybody go any ideas?

[Ken H.]

Anybody go any ideas?

See my questions above please.

[bmwmick]

Isolated from vibration - no change

Disconnected ALL remote lines e.g. Push to talk, remote volume - no change

Run with high beams and fog lights - no change

 

There is an electrical DEMAND at around 4K under acceleration that is enough to shut down the Starcom . . . this is a problem that has arisen in the last two weeks or so . . . Anybody go any ideas?

 

Yep,

Power the Starcom from the battery directly as a test. I doubt VERY much that anyting is dragging your electrical system down enough to mess up the Starcom but not affect the bike in other, more obvious, ways.

You might even try powering the Starcom from a separate 12V source (just as a test) to see if the symptoms change.

 

Mick

Tucson

[Rottweiler]

I had a similar problem with my sirius radio that turned out to be a defective power wire going to the sirius receiver. The ground wire had a break in it that only showed up when running the bike at full load causing maximum vibrations. When the break in the wire vibrated it caused horible static and noise. Eventually the radio would power off completly and power back on when it felt like it. This was a hard one to find, I would suggest running an entirely new power cable to your battery as a test. Good luck!

[KyleD]

As another poster mentioned, try using AA batteries instead of bike power. If that solves your problem, read on.

 

You might try bypassing or just replacing the Starcom inline fuse holder. Of the three I have dealt with, two were faulty. Your symptoms seem wierd, and this is an unlikely fix, but I'd use a higher quility fuse holder anyway. Other than that, I have had no problems with my Starcom.