The Pantera Place
"Your de Tomaso Connection"
Trim Screw Electrical Short
By Bill Taylor and Mike Drew
Lurking quietly in the Pantera’s cockpit is a potentially dangerous problem that
could easily lead to an electrical fire if the owner is incautious. The
left side turn signal trim enclosure mounts to the turn signal housing with an
8-32 x 5/16 inch (not metric!) countersunk Phillips-head machine screw.
The length of this screw is critical. When installing the mounting screw
for the driver side enclosure, be sure to use the OEM mounting screw (or at
least a replacement of the same length) and be sure that the screw does not
bottom out against anything.
The ‘chassis’ of the turn signal/high and low beam switch uses a threaded hole to accommodate this screw to secure the enclosure on the left side (the right side uses a #10 x 3/4 inch sheet metal screw). It can sometimes be a bit frustrating trying to get the short screw to pass through the enclosure and thread into the hole, and it might be tempting to use a longer screw.
The problem lies on the back side of the hole. Inside the switch assembly, just alongside the hole is a short spring. The spring is connected to the center (power) contact of the headlamp switch and pulls the center contact into contact with the low beam contact in one position and provides some “feel” while the switch is moved to the high beam position. The spring provides the total engagement force for the headlamp contacts in the low beam position.
The spring receives 12V anytime the headlamps are on. If the enclosure mounting screw is too long, the screw can pass through the turn signal enclosure mounting tab and contact the spring. If the screw contacts the spring, smoke and flames will be generated when the headlamps are turned on. This is definitely something you don’t want!
The switch could have been designed in many ways, but it happens to have been designed this way. The design is not a problem if the correct machine screw is used.
The turn signal switch from above, looking towards the rear (the turn signal stalk exits the bottom right corner of the image). The spring in the picture is connected to the center contact of the headlamp high beam/low beam switch and has 12V on it when the headlamps are ON. The threaded hole in the tab on the turn switch chassis is where the driver’s side turn switch trim housing mounting screw enters.
The turn signal switch enclosure is probably the very last part of the car a Pantera owner would ever think about. But there is a nasty surprise waiting for somebody who decides to substitute a longer screw for the one pictured!