Volt meter questions

[michael]

92 R100RT with 35k. The volt meter has always been a flickering think dancing around the red line on the high side. Last weekend took a 350 mile trip with my girlfriend who used a heated jacket. On the trip out with the jacket on it danced around the middle of the gauge where it should be. On the 170 mile return trip even with the jacket on the needle was dancing near the high red line. Without the jacket it was inside the first red section on the high side. Any ideas? Question: Can I buy a voltage regulator for this bike at an auto parts store?

[ME 109]

Use a decent volt meter/multi meter connected to battery to see where you're at.
The oe voltmeter is not a reliable indicator of charge.
A bosch RE57 regulator will allow you to charge up to 14.5, usually 14.2-14.3.
If you have a wet battery, the RE57 may allow too much charge, but it's good for agm types batteries.

[Nailhead]

My voltmeter reading fluctuates based on what part of the "LO" position my headlight switch is in, and it reads about a volt low according to a Fluke 116.

[Ken in Oklahoma]

My voltmeter reading fluctuates based on what part of the "LO" position my headlight switch is in, and it reads about a volt low according to a Fluke 116.

What do you mean what part of the "LO" position your switch is in. Are you talking about Hi beam vs Lo beam? As far as reading a volt low according to your Fluke, are you measuring voltage at exactly the same point to point. If it is and apples to apples measurement then I would believe the Fluke. The stock BMW analog volt meters are notoriously inaccurate.

As an aside, Harbor Freight flyeres often offer free DVM's with purchase. I have acquired more than I need and give them to friends. I have never noticed any significant differences in readings between the HF DVMs. I reckon that the Fluke DVM's et al will be designed and built better and will withstand more harsh treatment than the HF DVMs, but the value of a free HF DVM is, well, almost infinitely better than brand name DVM's. (Ignoring that you had to buy another item and you had to burn gas to get to the HF store.)

Shifting subject, I have sometimes taped or otherwise fixed a HF DVM to my tank and run the leads to the battery terminals. That gives you a warm fuzzy feeling about your charging system (Uh if your charging system is up to snuff.)

Ken

[Nailhead]

Ken, there is a little slop in the "LO" detent, and if I don't have that switch on the proper side of it, the voltmeter reads low(er). It does the same with application of the brakes, and swings vigorously back-and-forth when signaling turns.

I read the voltage at the battery posts, and the meter is a leftover from the oilfield, though paid for with much blood, sweat, and sleep deprivation.

I just chimed in to provide a further example of the questionable accuracy of the airhead voltmeter (as I've come to accept it). I've become comfortable with the foibles I mentioned above, and as the RS just spent most of the summer on the lift, I'm not really pursuing any sort of fixes right now though I really do appreciate the advice.

I've come to believe a vintage vehicle should have some quirks-- it's an essential part of the vintage experience, just as long as they're not potentially harmful or dangerous.

[ME 109]

Here's a current high charging issue on ADVrider forum. No cause found yet.

http://advrider.com/index.php?threads/1 ... v.1103791/

[SteveD]

Points to add re: our motometer vm's.

1. They read a tad better if the connections are very clean.
2. They're not accurate. They read a tad lower than a vm at the battery.
3. Eventually the needle dances all over the face and is a sign the dampening is kaput.

However, the real use is in knowing how yours normally reads, and noticing a sudden difference.

If the vm is suddenly lower during normal use, then maybe the charging has stopped working. That's a clue to taking notice if the GEN light is behaving as it should. Since 1981, ime x 2-3, this indicated a rotor stopped working (crack in winding each time)


If the vm is suddenly higher during normal use, then maybe the regulator is kaput. It'll need looking at or substitution asap before the battery cooks. Ime x1, this was a loose earth connection and another time a duff regulator.