We have a 1992 honda accord and we can't get heat from the heater, all the fans work, and we have changed the thermos stat but still no heat and now there is a yellow maitence light on

Feel your heater hoses. If both are hot, the core is circulating. If only one is hot-poor or no circulation of the core.
If the heater core is circulating, the temperature blend door may not be working to let blower air pass across the heater core, and into the vents. If vacuum operated, watch the vacuum valves as you move heater controls-you may spot the problem. Check that the vacuum line from the engine to the control switch is working and still connected. If not operated by vacuum, the controls may have cables to the heater case or may be electrically operated. You'll just have to scope it out. Good luck.

Make sure your fan is working properly. When you turn on the heater you are forcing the fan to cool the radiator. It may not be turning on automatically when it is supposed to. Let us know if this helps..

thermo stat is stuck

It could be the fan fuse, fan relay, a bad control head on/off switch or the blower motor is bad.

these cars were common for the cable on the temperature control seizing. if you look under the dash on the passenger side, in front of the center console, you can see the lever that should be moving. have a look and move the control, make sure that it is actually moving the lever.

change your heater core usually on pass side underdash.
have fun standing on your head to do it

Check the heater control valve. It is usually behind the engine up next to the firewall. Have someone inside the car move the heater control to heat. A lever on the heater control valve should move when this is done.

This valve allows hot coolant to enter the heater core inside the car. If this hot coolant doesn't arrive, you have no heat.

obviously the water pump was never fixed properly if it is still leaking, take it back to were you had it repaired and have them repair it properly. A number of problems could cause your vehicle to over heat.
-water pump not working properly.
-low antifreeze.
-air lock.
- rad cap not working properly.
-thermos stat not working properly.

The blower motor has died, you will need to replace it and last time I did one they were quite expensive (300 bucks), but the prices may have come down

You may have a clogged heater core, leaking heating cores still provide heat.