The sensor eyes only work when the door is closing. They will not prevent the door from opening. Your problem sounds like a bad receiver but you need to check the price. Putting that much money into a 17 year old opener is not a good idea.

Don, thanks for your reply. My car remote always opens the garage door, but won't close it. Same for my remote keypad just outside of door. But hard-wired button at inside door always opens and closes door. Does this indicate bad receiver board or sensors?
[I can't afford a new opener, but I can repair for $30(sensors) to $60 (board), depending on what part I need.]

This is a little different. If the main light flashes 10 times when the door reverses to the open position it is a door sensor problem. Make sure they are pointed at one another and the small light on each one is lit and not flickering. Tweak them a little. If you cannot get both lights to come on you have bad sensors. Just remember they must be pointed at one another for both lights to come on.

Sorry, Don, but I'm a little confused. Both little green lights on the two sensors mounted on 2 rails near garage floor are lit green, and seem to work, reversing decending door when the site line is broken. When door is coming down, but I then block the sensors, door goes back up and main light flashes 10 times. But I cannot get my remote to close the door even when there is NO blockage. So do you think I need new sensors or new sensor wiring, as was also suggested to me? But not a new receiver board? (I assume if the remote will always open the door, then the battery in it is still good, right?)

The sensors are working as they should. I have been confused also. I think at this point it is the receiver which is part of the logic board. The part number for the logic board is on the end of the opener where all the white wires go. It starts with 41A. You can get that number and check with Sears parts for the price. It may be that you will want to replace the entire opener due to the cost of the part.