1994 Ford Mustang Car Heater Blowing Cold Air

DELILAHQUINTANA

MEMBER
1994 FORD MUSTANG
6 CYL
2WD
AUTOMATIC
112,000 MILES

I have been having major car overheating problems. About a month ago my car started to overheat. I replaced the thermostate thinking that could possibly be the solution. It wasn't. Through suggestion I inspected for leaks. I found out that the water pump needed to be replaced. We replaced it and still heater in car not working. Symptoms are: Car heater blowing out cold air, cars temperture gauge bounces left and right in a jerking way, When gas is applied the tempature gauge stands still or moves left towards cool but when letting off gas peddle gauge moves up to hot again. What should I be looking for now to fix this problem.

3 Replies

MERLIN2021

MECHANIC
17,250 POSTS

Heater Core "” Plugged

WARNING: The heater core inlet hose will become too hot to handle if the system is working correctly.

Check to see that the engine coolant is at the correct level.
Start the engine and turn on the heater.
When the engine coolant reaches operating temperature, feel the heater core inlet and outlet hose to see if they are hot.
If the inlet hose is not hot:

the thermostat is not working correctly.
If the outlet hose is not hot:

the heater core may have an air pocket.
The heater core may be restricted or plugged.
If both are hot, the temperature blend door in the heater plenum may be broken or stuck.
Also with the gauge acting this way, it's low on coolant or has air trapped in the system.