[T3] Clock Repair - Lessons Learned

["Fuhriman, Mark" <mfuhriman@fugro.com>]

I finally got around to fixing the clock on my '69 Fastback.  It was
bothering me because it was one of the only things that did not still work
(now all I have left is that rear window defogger,,,).  I thought I'd share
a couple of tips with others to encourage everyone to get their clocks
going.   This applies to the (pre-'71?) "wind-up" type of clock.  I don't
know anything about the later clocks with transistorized workings.  The
basics are documented already in the vwtype3.org archives and on the
vwtype3.org website under 'fix it' and 'clock' (I think).  I'll just add a
few tips that I don't remember reading before.  My narration might ramble,
but it should help those who want working clocks.

On mine, the fault was that fusible link, exposed by the rear cover.  The
fuse link is commonly blown.  The cover was easily removed after removing
three nuts.  I had to break a plastic cover around one of the nuts, which
told me that nobody had been in there since it left the VDO factory.  With
the cover off, I did not bother with any further disassembly.  Too many
parts and springs and things that I didn't want to risk reassembling wrong.
All I needed to remove was the cover and nothing else.

The fusible link is a pair of metal tabs that just needed to be resoldered.
Look in there until you see a two solder-covered rivet tabs.  One of the
tabs will be on a bit of spring steel.  Those two tabs are supposed to be
stuck together with the solder on the tabs.  Move the tabs close together,
and re-solder the connection.  Use low-temp solder to make the repair (I
read somewhere that the spec fusing point is 120C).  I found my solder at a
local electronics parts warehouse.  I set my iron on the lowest setting,
barely let it begin to get warm, and that was warm enough to do the job.  I
probably could have just re-melted the solder that was already on the tabs.
The point is use the low-temp solder, and preserve the spring-loaded
connection to keep the fuse protection.  I read of some people fixing this
fuse by using thin wire and regular solder, but that leaves the circuit
without fuse protection.  (I read an archived post that suggested the most
common failure mode is letting the car sit long enough that the battery
charge dwindles to the point that there is not enough juice to rewind the
clock, and the resulting sustained current draw kills the fuse).

Look around for the wind-up mechanism.  You will see a small disk with a
pair of breaker contact points closed together.  Gently push the disk, and
the points will open up.  This "winds up" the pendulum.  Then you will
probably see the little gears begin to rotate, and the clock will tick.  The
ticking continues until the points close, and mini solenoid (inside the red
coil windings) pops the points apart, and the ticking resumes.  Check that
the contact points look clean and unpitted.  I used a piece of fine emery
board to clean them up (even though they already looked clean,,).

After I fixed the fuse, I hooked the clock to my bench power supply.  The
solenoid went *thunk*, and the clock began to work, but very sluggishly.
That's when I broke out the clock oil.  I got it at a local clock repair
shop for around $4.  A small plastic bottle with a long steel needle spout
to reach remote nooks and crannies.  Don't use 3-in-1 or any other vegetable
oil.  WD-40 might work temporarily, but it won't last long.  On mine, the
works weren't dirty (they're sealed pretty well behind the cover), but I
suppose at this point you could give it a shot of electrical contact
cleaner.  I added *one* drop of clock oil to every pivot point and other
contact area I could find.  The clock instantly began to work without
missing a beat.

There is a slot-head screw back there to adjust clock speed.
Counter-clockwise speeds it up.  I had my clock hooked on my bench power
supply for a few days, and I found that a slight ~1/8 CCW turn made it run
at just about the right speed.  I guess that the long-term accuracy will be
temperature-dependent, but SF Bay Area temp variations are not extreme.  It
feels good to look at my nice uncracked original dash and see a working
clock  :)   Hope this helps somebody.

-Mark Fuhriman

-------------------------------------------------------------------
List info at http://www.vwtype3.org/list or mailto:help@vwtype3.org