The headlight switch for the 914 is an insanely expensive item - something
near $400 new! Luckily, there seems to be a fairly good supply of used switches
on Ebay. I recently bought a switch, not because I needed the switch, but
because the insert was wrong - it was the rare, early green fog light insert.
I'd wanted this insert, but didn't want to spent $30 at AA for one! I won the
auction and got the switch for $9, including shipping.
After extracting the insert, I checked out the switch - the instrument
rheostat wire was bent on the end and popped out. I decided to take the
opportunity to see how the switch was made and if it could be repaired. Based on
what I learned, here is a disassembly procedure with some photos of the
internals. Hope this helps out anyone who might need to rebuild a switch. Note
that there are two 914 switches - the "early" skinny one (the one you
see here) and the "fat" late one. I don't know how much the fat switch
differs...
- Remove the knob by unscrewing it from the shaft.
- The contact plate is crimped onto the body of the switch at the corners.
If you have a lot of patience, time, and plenty of small screwdrivers to
break, you can try prying the corners away. Or, you can take the easy
approach and use a Dremel cut-off wheel and simply cut the corners away.
Don't worry about how you'll get the top to stay back on - I have an ugly
but very effective way of doing that in the last step.
- After the contact plate is freed at each corner, it will probably pop up
near the front of the switch. To remove the contact plate without damaging
the switch internals, you will need to hold the rheostat assembly (at the
back of the switch) in place. Hold the switch by putting your fingers of one
hand under the body and your thumb on terminals 58a and 58b. While holding
these terminals down, slide the contact plate up over 58a and 58b, remove
your thumb and slip the plate off. The rheostat will stay in the back of the
switch. After removing the contact plate, the switch should look as below
(the contact plate is flipped over to reveal the contact pads):
- It's pretty easy to see how the switch works. The contact slider block is
keyed to the shaft. Each contact slider (there are three) is backed with
small springs to press the slider into the contact plate. The bottom of the
contact slider block has two springs that push plastic pins into detents in
the body to "click" the switch into the three positions. All of
the contact plates seem to be silver plated. The entire assembly is coated
in dielectric grease for lubrication and to prevent arcing. The rheostat is keyed to the
shaft and rotates a contact plate wiper against the resistance spring. Note
that the rheostat assembly is electrically separate from the switch part.
- OK, let's finish disassembly. Carefully lift off the contact slider block
from the shaft. There are two small springs in the bottom of the switch that
push the plastic pins down - they may fall off into the switch body. Leave
them there until later. Put the slider block aside. Pull the shaft out of
the rheostat, and put it aside.
- If your rheostat is OK, leave it alone! If you need to remove it, be aware
that there are two small springs that will pop it apart if you simply pull
it out without holding it together. The retaining plate is simply held by
shoulders and slots in the switch body. Put your thumb on it and pull
upwards on the terminals - try to hold it together. Once removed, let the
springs move the plate off of the slider and put the parts aside.
- Below is a picture of the disassembled switch:
- Repair will depend on the problem with your switch. Damaged rheostat
springs can be repaired with careful use of tweezers. Damage to the sliders
can be repaired with good parts from another switch. Damaged contact plates
will need to be replaced with a good part from another switch. Worn out
contact slider block pins can be replaced with good parts from another
switch.
- Reassembly is fairly straightforward. Use contact cleaner and clean the old
grease off of all parts. Coat the bottom of the switch bottom, spring guides
and springs, contact plates, pins, and contact plate with dielectric grease.
Reassemble the rheostat by stacking the retaining plate, rheostat slider
plate, springs, contact slider, and rheostat plate together and insert the
assembly into the switch body (make sure the retaining plate is oriented so
that the tabs at the top limits the rotation of the rheostat slider plate).
Slide the shaft into the switch body and key it into the rheostat.
Reassemble the contact slider plate - use a good amount of grease on the
springs and pins to hold them in place so that you can slip the slider plate
onto the key in the shaft without the pins falling out into the switch body.
Make sure you orient the contact slider plate as
shown in the top photo. Slide the contact plate back on the top and over the
rheostat contacts.
- If you carefully bent the corners out when you disassembled the switch,
you may be able to bend them back to hold the contact plate in place - good
luck. If you used a cut-off wheel as I suggested, you could use epoxy to
reaffix the contact plate, but you're in trouble if you should need to disassemble
the switch. Instead, use an ugly, but effective and removable way of holding
the plate on - a tie wrap! See the photo below for where to run it through:
- You're all done. Use continuity tester or DMM to check the switch
operation before installing. Diagrams of the switch internals are at the
Pelican Parts web site in the 914 electrical diagrams area ( http://www.pelicanparts.com/
).
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