Good day all,
Progressing along on my 1989 XJS and taking a break from the 76 XJ12. An odd issue has randomly occurred, the kick-down switch is blowing fuse #5 and is showing a constant 12v with key on. The second I have the switch connected to the momentary microswitch or even to the other lead, I blow the fuse. The only thing I've done electrically is install a new-ish instrument printed circuit board and independently wire in a new radio, pulling a constant 12v from a post on the firewall and using a keyed fuse tap on one of the seatbelt fuses. Neither of these two situations would cause a fault within the trans switch/solenoid.

I don't really know anything about automatic transmissions, so I'm flying a bit blind here. I've been searching around some GM forums to see if any of their 400 transmissions present a similar issue, but I'm having no luck. Why would I suddenly be having a constant voltage issue, one that outputs so much current, and how would I go about correcting this? I suspect I'll have to drop the trans pan, but any other guidance?

 

Key-on voltage at the kickdown switch is correct


Not entirely clear on what you've said here

I suspect the kickdown switch as broken internally allowing a direct voltage-to-ground short, thus blowing the fuse.

Cheers
DD