Heater bad

[03 Pony]

Temperature gauge started acting funny (it would just float back from cold to hot and back to cold in two seconds) and now the heater just started blowning cold air this morning. Any ideas?

 

[flexiclese]

check to make sure the temperature sender is connected properly.
If that checks out its probably a thermostat that is stuck open and not letting the engine get to or maintain propper operating temp.

 

[03 Pony]

Okay thanks. The overflow was empty too, so I will have to get some coolant.

 

[timeless2]

Thermostat sounds like the culprit, provided your coolant is of quality and proper level, with no air in the system.

You can test it by removing it and boiling it in water to see if it even opens at the right temp (use a candy thermometer to check the exact temp).

 

[flexiclese]

It will be really obvious if the thermostat is bad, when you remove it the plunger will be stuck open, eg not in contact with the ring it is supposed to sit inside of.
If the thermo was stuck closed you would have the opposite senario, your car would run hot
make sure you check the temp sender 1st for propper operation to possibly save yourself some work