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On 20 Jun 2005 at 11:10, James Montebello wrote: > Ultimately, it's usually cheaper and easier to just buy another VR. I completely agree. I've never been able to rejuvenate a bad one, but I suspect I could if I replaced that resistor, polished the contacts, and then readjusted the whole thing. It's a LOT of work I modify the Bosch mechanical VRs that I sell. I add a diode that should make them last considerably longer. I really don't know how much longer they might last this way, because I've not yet worn one out. > 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. Should be true, but I'm working with a 412 customer right now to get him a good VR for his early alternator system. This system originally came with a mechanical relay VR, but he bought a solid state aftermarket VR from JC Whitney. Both his old VR and the brand new one regulated at 13V. The transistor in the old one was leaky, so I've now replaced it to see if this changes anything. I'm afraid that this design dissipates too much power in that transistor, which then overheats and damages itself. It's a linear regulator, rather than a PWM (pulse width modulation) approach, so it has to run hot. This was is quite simple, but I'm not impressed with its performance so far. It's another work in progress.... -- ******************************* Jim Adney, jadney@vwtype3.org Madison, Wisconsin, USA ******************************* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ List info at http://www.vwtype3.org/list | mailto:gregm@vwtype3.org ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~