My heater just blows cold air 2000 tj

common for this vehicle to have clogged heater core

Could be a thermostat problem or your heater core!

check coolant level sometimes low level will cause no heat

I would return the vehicle to where the work was done. It sounds like something such as the blend door was not reinstalled properly, or something wasn't reconnected properly.

Have had the same problem 2000 ford expedition. got it working good now

Does temp gauge on dash show normal temp? If so problem is with the controls. If sytem cycles through normal controls IE, defroster, floor,bi-level and redirects air properly check to make sure door control is functional for heater core. If door is not opening then you will never get hot air

my 2000 saturn sl blows cold air with the heater on. I changed the thermostat,and checked out my heater core.Still blows cold air.

sounds like 1 of the controll wires cam off the heater box to me

your thermostat is stock replace it

does the car not heat up in general? Whats the temp gauge doing and how long of a ride have you tried this for?