Alternator/Voltage Regulator issue, Alternator light is on until rpm's increase Options

[PDXMike]

My alternator light stays on after I start the car. It was dim, and it would go off (and stay off) as soon as I got the RPMs up over 1000 or so. I did eventually find a faulty connection between the battery and the Voltage Regulator, which I thought would solve my problem. Instead, I now have a similar condition except that the charge light is on full bright (not just dim, like before) until I blip the rev's up a bit. It will still go off and then stay off for the rest of the time the car is running.

With the car running at about 1000rpm I am getting 14V at the battery. Pulling the VR and shorting D+ to Df results in 16-17V at the battery, so I am assuming my alternator is good.

I thought there was something going on with the VR not applying enough voltage to the field at start-up, so I ordered a replacement. They new Voltage Regulator is an AC/Delco part, not the OEM. I have exactly the same issue with the new Voltage Regulator.

Any ideas?

Thanks!

Mike

[Rand]

I haven't heard of bootstrapping a 914. It is basic electrical circuits, not a computer. My gen light only came on once, and a quick wiggle of the VR fixed it which pointed me to cleaning the terminals. Never happened again. If you only could be so lucky, but point being, if the light light's on, something IS wrong. No way in hell should you write it off as normal. It comes on for a reason which usually indicates a dirty electrical connection. If you start introducing LED lights and such, it gets more tricky because of resistance changes.

[mikesmith]

I haven't heard of bootstrapping a 914. It is basic electrical circuits, not a computer.

As others have said, it's quite normal, and the term 'bootstrapping' significantly predates its use in computing.

Alternators require electrical current in the field coil (excitation) before they can generate any current themselves. This current is supplied through the alternator warning light. Once the alternator is spinning fast enough, its internally generated current will take over (self-excite) and none will flow through the warning light (causing it to go out). This is the 'bootstrapping' process.

The current through the warning light is much smaller than the field coil current during normal operation, and it can be affected by many things - the selection of bulb, contact resistance all through the path (fuse, connectors, bulb socket, etc.). This will affect the speed at which the alternator's internally-generated field current takes over (lower bootstrap field current -> less current generation per rpm -> higher rpm required to self-excite). It's also possible for a partial failure of the field coil rectifier to produce these symptoms.

From a practical standpoint, as long as the light comes on before you start (this is critical), and goes (and stays) off in normal operation, you're fine and you probably have better things to worry about.