Measuring alternator output

[moose]

What is the best way to measure alternator output on the S?

I'd ideally like to be able to monitor it while riding on the road, but also would like to have it available for diagnostic purposes. I think the system voltage is, and has been for awhile, a bit below spec.

And, where is the voltage regulator, and how is it replaced?

Thanks!

[markjenn]

The S (and most BMWs) have a fairly generous electrical capacity (I believe it's 600W), so unless you're really adding the farkles, it's seldom a problem. But if you want to monitor the system, I'd mount an aux voltmeter such as this one:

http://www.martelmeters.com/products.php?cat=1&action=detail&id=55

It is easy to note when you're in a net discharge condition as the running battery voltage drops from a typical 14V or so down to 12.5V.

- Mark

[davidgiannini]

Moose, looking at the manual it appears that the voltage regulator is attached to the alternator.

[davidgiannini]

Lets see if I can post a pic for you..

[bikpaintr]

The best place to check charging voltage is right at the battery. Not the easiest thing to get to on the S but at least you'd know if your output is low. If it is check the tension on your alternator belt.

[J. Dial]

Don't know if you guys are aware of it ot not, but the alternator on your s is a Toyota manufacture. I think this is kinda cool as brushes and bearings have to be easier to come by. Yes, the reg is enclosed in the alternator.

I put a new battery in my S last week and ran an insulated wire and connector off the positive side of the battery to under the seat. This is to facilitate winter charging and run voltmeter tests.

[moose]

Thanks for the help!

It's not belt tension, but I will add the voltmeter. Since the diagram mentioned testing the alternator with the BMW diagnostics tool, I'll run by the dealer to see if they can't do a quick check.

With regards to the Toyota source comment, I read on an earlier thread that it's a Bosch alternator. Either way, if it's a standard item, it might be cheaper to purchase that way than a re-badged BMW.

[davidgiannini]

I have the accessory socket. been using that to measure voltage.
Let us know if you find a replacement alternator form Toyota.

[Joe]

If your checking the Alternator by voltage measurements make sure you load the battery down by turning on all circuits to the max( high beam and heated grips on max etc. then read the voltage across the battery while running at a fast idle it should be 12-13v.

[moose]

How did you use the accessory socket to monitor voltage? did you get a BMW adaptor plug and tap the leads?

[davidgiannini]

Yup, I have an adapter plug and some extra leads that came with a battery tender.. I just clip in the leads from my digital multimeter.

[RBMann]

Markjenn

Your meter idea looks a lot like the one I had on my bike until the HID fried it.

http://www.lascarelectronics.com/products.cfm?STOCKNO=EMV%201200&CFID=8951843&CFTOKEN=83959491

I wonder who really makes them. Martel=$34 Lascar=$25

RB