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generator / regulator question

I was slowly loosing my battery charge so i cleaned the connections then connected an amp meter and noticed that when the charge got above about 10 amps the amp-meter-needle started oscillating wildly. The oscillation seemed to range from about 20 amps down into the negative teritory at a frequency of about 5-10 times a second .

I had a spare voltage regulator so i plugged in in and got a steady 30 amps - without oscillation - with at about 2000 rpm (guess).

Ok so all is well now, but what caused the oscillation displayed on the amp meter and (assuming it was the voltage regulator) what if anything can be done to repair it?

Also in the future can someone tell me what is the simplest method to bypass the voltage regulator so i can measure output of the 6V generator...

when is it appropriate to measure the voltage output and when is it better to measure the amp output. or does it matter which one you measure.

thanks in advance.

Reply to
t
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The regulator is mechanical (relays). They wear out. Toss it in the dust bin.

See the article on my web site: "How do I test my generator?" for measuring output.

A voltmeter in the car to measure actual battery voltage (not the voltage at the dash) while charging will tell you more than an ammeter.

Speedy Jim

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Reply to
Speedy Jim

The VR consists of a relay which switches power to the field coil on and off. It does this faster than an ordinary meter can follow, so that what your meter indicates is pretty much DC.

A worn out VR can develop a problem where the vibrating contacts slow way down. I'm not actually sure what causes this, but I suspect that it is due to the contacts welding themselves closed and then breaking free. It may also be due to the wire wound resistor on the underside going open, which would change the circuit characteristics and the self resonant frequency.

At any rate, this is a typical end of life senario, and the only solution is to replace it.

Disconnect the DF wire from the generator. Ground the DF terminal. Run the engine up in rpms while you measure the voltage. Do this only for a few seconds at a time. Because there is no VR in place the voltage can go much higher than normal if the generator is healthy. Don't overdo it; you'll damage something.

Voltage is generally easier to measure, and will tell you most of what you need to know.

I have a FAQ on charging systems; if you want a copy, email me.

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----------------------------------------------- Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA

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Reply to
Jim Adney

thank so much for the replies. i am going to take apart the voltage regulator and see if i can find any evidence of damage to the contacts...

thanks again! tony

Reply to
t

I think you'll find that interesting. While you're doing this, check the wire wound resistor on the underside. It's about a 4 Ohm resistor, but I think you'll find that it's open. You'll have to open one of the relay contacts inside to measure it, however.

In my experience, that resistor is alway open when the VR is bad. I suspect that the resistor eventually ages and one of the wires break. Once the resistor has opened I believe that the contacts arc much more and that contact wear thereafter is quite rapid.

I have a mod I do to Bosch regulators which should make them last much longer. I can sell you one like this, or you can just buy a standard Bosch one and expect it to last 5-7 years.

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----------------------------------------------- Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA

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Reply to
Jim Adney

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