Q: Blowing cold air no heat

asked by on

I changed the thermostat it's still blowing cold air what could be the problem
My car has an automatic transmission.

Since the thermostat has been replaced, there are a couple of other things to look at. The heater hoses going through the firewall in the engine compartment to the heater core behind the dash should be checked. They should be as hot as the other hoses to indicate that coolant is flowing through the heater core. If the heater hoses are not hot, then it is possible that: the heater core itself may be clogged, one of the heater hoses may have collapsed internally and is blocking coolant flow, or the heater control valve is not functioning properly. The heater control valve works by vacuum. When HEAT is selected, a vacuum signal is sent to the heater control valve to open and allow coolant to flow into the heater core to provide heat. If the heater control valve diaphragm is broken internally, or the valve is not receiving enough vacuum from the engine due to a broken or detached vacuum hose, it will not open. Also, the heater controls can be at fault if it is not sending the proper signal to the heater control valve to open.

Have a certified technician look into the no heat problem to isolate the correct cause.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1,000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!
  1. Home
  2. Questions
  3. Blowing cold air no heat

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: I changed my battery and now when I turn my key there is a very loud buzzing noise

The noise is most likely coming from the shift lock actuator. It may have been damaged from the previous battery or jump starting the battery. If shifter unlocks normally they the solenoid may just need replaced.

Q: Truck stalls, starts back up after 2 min, stalls again starts back up after 2 min, now good for 1 month and it happens again.

Hello, thank you for writing in. Unfortunately you already know that the hardest part is going to be catching the problem when it occurs. With intermittent issues, you must wait to diagnose until it happens again, find damages or flaws...

Q: Car not cranking.

One thing that may have happened if the engine was flooded is that the cylinder walls may have been washed down by excess fuel. Once this happens the engine has a distinctly different sound when starting. Also, even spraying starting...

Related articles

P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the...
P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.