[T3] Why early clocks fail

[crash 69]

So using a trickle charger would be OK, right?

On Mon, Aug 8, 2011 at 9:41 PM, Jim Adney <jadney at vwtype3.org> wrote:

> I just fixed an early (up thru '70, the ones with the white plastic
> backs) clock for someone who asked what goes wrong with them. I
> thought this might be worth sharing with everyone.
>
> These early clocks use a solenoid to wind the clock every minute or
> so. When the spring winds down a bit this lets a set of points make
> contact, energizing a solenoid which "kicks" the winder and opens the
> points. I believe this is typical for all car clocks up to around
> 1970.
>
> There's a "fuse" in these clocks that opens up. This typically
> happens if the car is left in storage with the battery installed. As
> the battery discharges, it gets to the point where no longer
> sufficient voltage to kick the winder, so the points stay closed and
> draw current continuously until the fuse blows. The clock normally
> draws current for only a fraction of a second, and that current
> normally never gets large enough (or long enough) to trip the fuse.
>
> The "fuse" is actually a tiny rivet made of very low melting point
> solder. I repair it by melting it and rejoining the connection. I
> also add a diode across the solenoid to minimize arcing when the
> points open. Then I flush out the works and lubricate each of the
> pivots with clock oil. The repair is usually pretty straightforward,
> but these clocks never kept very good time.
>
> In 40 years, I've only seen one of these clocks where the bearings &
> pivots were actually worn out.
>
> The moral? Disconnect either the battery or the clock if you park the
> car for a long time (months.)
>
>
> --
> *******************************
> Jim Adney, jadney at vwtype3.org
> Madison, Wisconsin, USA
> *******************************
>
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