Air in the water system.
It doesn't really blow it out it just warms the cold air.
heater core possibly plugged and leaking
The front expansion valve is clogged.
Could be a bad thermostat.
Your heater will blow cold air only.
One of the reasons a 2000 Jeep Cherokee heater would randomly blow cold air and then hot air and then cold might be that there is a problem with the hot/cold duct. The air or a vent might be inadvertently blowing periodically.
Low coolant in the system. Defective heater control valve. Clogged heater core.
engine not warm, low coolant, or stuck thermostat
you would have to see a mechanic about that problem
Poor coolant circulation from a plugged up heater core. Try flushing the heater core and replacing the thermostat.
you need to replace your heater core
it wont blow heat itll blow cold air
heater switch needs replaced
the blown head gasket would make it over heat. but it wouldn't cause the heater to blow cold, it should actually blow hot if that is wat happened
you are low on coolingliquid !
Possible causes are, low on coolant, thermostat stuck open, clogged heater core or vacuum scorce not getting to the heater control.
check thermostat, might be stuck closed.
Insufficient amount of coolant or thermostat not opening
I would change the thermostat first. If that dont work change water pump
heat core. leak. thermostat. no antifreeze.
The heater valve could be failing to open for one reason or another.
No, not if it's on a heat setting. Most home thermostats have a "Fan" setting that will blow cold air if the attic is cold.
you may not have the heater water hoses plugged in