So I'm on downwind, select a touch of flaps on my momentary flap down switch, and I soon find the flaps are still extending. Pushing the flaps up button does nothing. They continue past the limit switch until the flap motor hits the mechanical limit and pops the breaker. From the cockpit I could look directly down at the ground where the flaps normally are. Not to mention the fact that it felt like a massive speed brake. I was able to land with very little pitch up authority left. This all happened in about, oh.. 25 seconds.
The real bitch of it was this. Get it back to the hanger, reset the flap motor breaker, select flaps up and everything works. They are back to obeying their limit switches like normal. I probably ran those things up and down 50 times and couldn't get it to fail again. Checked all the wiring, couldn't find a problem. Until... I caught it. The down flap relay fused and got stuck on, thereby bypassing the limit switches, and pretty much everything else, only being stopped by the flap motor blowing the breaker. Once it cooled down the relay would release and return to normal operation.
So, even if the relay is wired correctly, and works as designed sometimes, doesn't mean it will on short final. Relays get old, like everything else. If I were you, you might consider new relays. (if your airplane has them I guess)
Tom