[mysticone]

Just a few days ago, the heat stopped blowing hot, and is now lukewarm...there is antifreeze in it..1997 toyota avalon

 

[Dave's]

Where's your temp gauge sitting? Sounds like the T-stat probably stuck open.

 

[mysticone]

it rises to half way

 

[BKAvalon]

Clogged heater core, air in the cooling system (change coolant lately?), problem with valve that let's more or less coolant into the heater core, problem with the temperature dial not opening or closing that valve, problem with driver setting heat to lukewarm rather than hot...

 

[Dave's]

Pretty much what BK said. Usually if it changes suddenly and nothings been done which might have caused it then the failure is the t-stat or the valve (if so equipped). Clogging of the heater core can happen suddenly but usually it's a gradual thing unless (again) something's been done to the system.