Under the bottom of the seat(s), there is a metal "comb", that has teeth in it. When you push or pull the lever, it removes a latch which fits into one of the teeth, which holds the seat from moving. So when you release the lever, the latch will then spring back into the comb to fit into the slots so seat won't move. Sometimes you've got to jerk the seat forward or back a bit, to get it to fit into slot---that's the "clunk" you hear.
So if the seat is moving by itself, then something is broken or wrong.
Most likely, the spring that pushes the latch into the comb is bronken or else the latch is just stuck open. You can remove the seat easily, take it out of car, and examine it. It just might need some WD40 to spray on latch so it'll loosen and spring shut. Or maybe the spring is detached so it doesn't force the latch shut.
You can also get a replacement seat at junkyard for about $30-50 if you need to.
The turn signal lever is broken--or rather the little switch which holds it. And inside that switch is also another spring which will then cause the lever to normally bounce back to neutral position. Since the mechanism is broken, the signal lever pulls back immediately into neutral unless you hold it.
To fix it, you have to take apart the steering column, which means taking off the covers just behind the steering wheel. Then you have to replace the little box that holds the signal arm, but that's kinda hard, and usually it's best to have a mechanic do it.
The headlights working only on high beam. Need more info. Do the head beams work in both dim and high settings, or only in high setting where they should work. Does this mean that the low beams dont' work at all? There are some fuses which might be important for that to work. If both headlights do not have low beams, sounds more like a short to me, rather than mechanical failure---meaning the bulbs burned out and need replacing. However, the low beams have always burned out much quicker than high beams, only because you always are using low beams, even with high beams on. So it could be as easy as replacing the bulbs. Otherwise, the short will be harder to find, again by a mechanic.
I've been driving a 1991 Geo Prizm taht's been pretty beatup. I've had to spend few thosuand bucks to keep it running. If I'd known I'd spend that kind of money, I would have gotten other car. It's been a great car, but it's nickeled and dimed me to death, meaning I"ve spent way too much on an old car. it mgiht be time for you to sell yours and get somethign much newer so that you won't have things broken on it. I know it's hard to part from a favorite car, but once you get driving a car in better condition, you'll won't regret it.
