Prius key-fob latch fix

My base-model Prius doesn't have "Smartkey", the radio-based sensing system that allows entry and startup without having to insert a key or a fob into a slot. So I have to physically push the entire fob into the hole in the dash when starting the car. I keep my keys attached to my person on a fairly short lanyard, which isn't quite long enough to reach from my belt to the fob-slot, so I simply unclip the fob from its embedded metal key using the built-in latch. That way, the hard key remains attached to *me* which helps avert any key-locked-in-car scenarios.

The problem is that the tiny slide knob to disengage the key latch is not very robust, and the thumb-bump that sticks up out of the fob tends to break off. After having one fail and using the other fob for a while I noticed that its bump was beginning to weaken too, and threw together a quick description of the problem:


I posted this to one or another forum and also sent it to my dealer, who said that it wasn't possible to order just the backing plate for the fob but he was kind enough to simply hand me an entire "dead" fob he had kicking around that didn't belong to any particular car anymore. This third good latch piece served adequately for a couple of years thereafter, but alas its days were numbered as well.

Here we have still-barely-intact [circled] and broken off.

It's not a showstopper, as a fingernail can be used to push aside the remaining piece of plastic that retains the slide-latch in the fob, but it's kind of annoying. The part of the fob-back that encloses the latch and its spring has no clear way to come apart, and I had just assumed that the parts were assembled in and then the housing glued together around it so it was more or less non-fixable.

Wrong! It turns out that the little plastic bit can be pulled out of the slot in the latch piece itself [which is *metal*, by the way] and that lets the entire latch piece and spring come out too. Okay, so obviously I just need to construct a stronger replacement for the plastic bit.

The barely-intact one, left, is basically toast at this point too. The outer nub is attached by a *very* thin web of plastic that simply can't take the stress of repeated pushes. Why, I can't imagine -- it would have been easy enough to make the entire upper half of this thicker.

The frugal New England "save everything" philosophy pays off: in one of the scrap metal boxes is a piece of aluminum frame that used to hold a hard drive, a small area of which looks like it'll be about the right size and right-angle shape to go in there.

A little carbide-wheel work later, I've got a base piece cut out and ready to shape down to fit. The foreground shows how the plastic handle fits in underneath the latch bar, which I'm trying to duplicate.

The piece has to insert cocked-in through the latch hole and then level out, and it can't stick too far through in the process or it won't go in. The plastic piece may be able to bend slightly to facilitate this, but my metal one clearly won't and needs a little relief beveling underneath.

Continued filing-down of the "tongue" brings it to an approximate match for the original piece.

The length of the tongue is critical. It has to be long enough to retain itself well under the hole edge, but short enough to let the upper *side* of the handle bear against the latch piece where the arrow is. If the tongue is just a little too long it tends to hinge against the end of itself, letting the new handle tip right back out of the hole when pushed over. Almost lost the damn thing when testing it the first few times.

Eventually my new thumb-piece is shaped down well enough to stably remain in place while being pushed over. This really isn't a particularly good design to begin with; it sort of depends on the latch spring continually pushing everything toward the left to hold it all together even in the original configuration. That doesn't necessarily stay true in the brief moment of snapping the key back into the slot.

Happily back on the ring, and much more accessible than digging a fingernail into that tiny slot.

My replacement piece is a simple right-angle handle with a fair amount of slop around it, and could conceivably benefit from some additional metal hanging over the outside of the latch slide without that making it impossible to insert. If this one jumps out and leaps to its doom someday, I might work up a fancier and tighter-fit version.

_H*   100508