Virginiafiretruck,
I looked at some of your pictures and noticed your truck has a alternator...is this true!
In order for the rig to keep running, the coil must be supplied with power even after mechanically turning off the key switch.
If your dinking under the dash was the really the cause of this, then maybe two adjacent wires or wire ends got mashed together so they touch. This would have to be the BATT wire on the switch and the IGN wire...take a look for wires that touch, but shouldn't.
The alternator thought was that maybe you had DA #1 tied to the coil, and possibly there was a diode in the pigtail that failed (closed ?) and now the alternator is back feeding the coil.
Something is powering the coil AFTER the ignition switch. I don't think the switch itself could fail internally and not open the circuit to the coil, but I have been known to be OTL before.
If this was truly a cause and effect deal with the install of the speedo adapter, then it is probably a mechanical wire mash situation or a missing flat washer laying across two terminals of the key switch.
Stuart
