Type 2 WOT Switch disassembly

[Scott Mockry <scottmo@teleport.com>]

>Phil asked:
>Has anyone ever take a Type 2 (overlapped and potted) WOT switch apart?

Yes, I had one of the "Type 2" style throttle switches apart that was
apparently damaged by the Monkey Lads before I received it. The Monkey lads
had applied +12V and ground across the WOT terminals and the internal
contacts were vaporized.

This new style throttle switch for the MC designated engines has the same
part number as the original design switch, 

Bosch # 0 280 120 308 

It uses a better connection terminal design inside for the idle and full
throttle switches. 

The previous design just lapped the two terminals together side by side,
and then they were soldered. This resulted in a poor mechanical connection
and eventual failure due to the cracking of the solder joints from thermal
cycling and vibration.

The new Type 2 throttle switch has a forked terminal strip inside which
allows the flat strip connections from the idle and full throttle switches
to be inserted and crimped before they are soldered. This improved
mechanical connection "should" lengthen the life of these switches.

The orientation and mounting of the internal idle micro-switch and full
throttle contacts is very similar as the original design.

I have taken apart over 15 of the original design throttle switches, and
they all had cracked solder joints and intermittent operation.  Best bet is
to replace the switch with the new design, as I have seen repaired original
design switches fail after about one year.

Many people are hesitant to replace these original design throttle switches
as they often test ok, the moment you are  probing and fiddling with them,
but then the WOT switch portion doesn't work later as you are driving down
the road. The WOT mixture control and boost control for the MC engine
relies on this switch working correctly, so IMHO, it isn't worth taking the
risk by continuing to use the original design part.

BTW: the original design throttle switch uses a plastic cover with four
tangs that has a glued (solvent glue) seam down the middle of the body of
the switch. The new design throttle switch also has a plastic body but with
a flat lid or top piece, which has black potting (epoxy) material sealing
the top edge.

HTH
Scott Mockry