I have a 1998 s10 and the heater switch will only work on dash ve

defrost does not work it does not blow at the top windsheil

In my 1998 Honda Accord Lx the hot air does not come out of the heater vents in the floor, the same is true for cold air in the middle vents on the dash. The side vents on the dash work fine.

sounds like you have a vacuum problem

your a/c and heater blow thru the defrost ( top of dash? ) and the vents. Or defrost/or the vents.? and not on the floor? Well all of these should work. can you hear the motor inside the dash turning to they're perspective spots on the dial the motor pulls a cable and closes or opens appropriate doors as the selector switch is moved. if not the switch may be faulty. and you can get it from a parts store or dealership. CK the parts store's first they will be cheaper and will be able to give you a look at what needs to be done to replace it. But it can be done on most "fine " cars in 20- 30 min with minimal hand tools.

you have a bad control switch.

i had this exact same problem with my 98 explorer. your blend actuator (blend doors) are not morking. these are on the passenger side under the dash. getting to them will be dificult, but it can be done. you will need to take apart the heater box, to fix them. (the big black box under the dash).

I already posted my solution.

blend door not working on that side or obstruction in the vent from heater to dash vent on that side ..have kids with toys or ?

i would say its in the dash unfortunately you will have to pull it out to inspect.