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Re: [T3] Voltage Regulator

An old electro-mechanical VR like the Bosch unit are basically two position
relays that either allow current to flow from the generator to the battery, or
force it to flow through a large resistor to ground.  The current through the
relay determines which way it will flow.  Above a set point, it will go to
ground.  Usually, this is done with a electromagnetic coil, a ferrous pole
piece, and a calibrated spring.  If the coil fails, the switch always allows
the current to flow into the battery, which overcharges it and often causes the
battery to fail, too.  If the spring fails, the current never flows to the
battery, which quickly discharges (and this, too, can kill the battery).

To fix the coil, you'd need to either replace that coil or re-solder the
connection in a way that doesn't throw off the calibration of current to
pulling force against the spring.  The former will cost more than a new VR, and
the latter is very difficult to do.

To fix the spring, you'd need to replace it with a spring of exactly the same
force as the one that failed.  If you have a source of these, this is easy.

Ultimately, it's usually cheaper and easier to just buy another VR.  Better
yet, buy a modern solid-state VR that uses electronics to control the current
flow.  These will last a lot longer than the mechanical units.  Most of the
alternator conversions sold for these cars use alternators with built-in
solid-state VRs, so the external unit becomes unnecessary.  

--- "Iturzaeta , Joseph " <JIturzaeta@kbhome.com> wrote:

> How exactly does a voltage regulator work? I replaced mine over the
> weekend. I took the cover off the old one and it looked fine. It looks
> like a couple of electro magnets that operate a couple of switches. My
> car runs better now that I replaced it, so is there a way to fix my old
> one so if the new one some how burns out I can have a spare? Is there a
> way to check it off the car or does it have to be hooked up in order to
> check it?
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> List info at http://www.vwtype3.org/list | mailto:gregm@vwtype3.org
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