Ok so quick question and hopefully semi simple, got an 87 Cherokee xj..problem is you can only tell in the winter or when it rains but my heater only blows warm air from the defrost vent, not a lot and it only blows air from there, also in the winter water will build up on the passenger side floor board over time. Only thing I could think of is bad heater core? Input bout this would be good thanks

 

Here is a bad picture of my window in the snow

 

check your thermostat. Mine had weak heat, bought a new stat... went to install... found there wasnt even one in there.

 

heat works now tho!

 

Right on thanks man!! I'll do that this weekend much appreciated

 

When you change out you t-stat you may as well flush your cooling system. Flush the heater core separately and in both directions. You said it only blows out the defroster. That would mean either that you have a vacuum leak or your blend door is not operating correctly. Since you have an 87 and you my have a heater control valve. That is if it hasn't been removed. If you still have one remove it and plug the vacuum line to it. It is not needed. The newer XJ's don't come with them.