When driving heater starts blowing cold air?

Hi,

This is an odd one because when the engine RPM's increase, coolant flow also does. That should make the heater work better. Also, you indicated everything has been replaced and the temperature gauge indicates normal operating temperature.

I have a few questions. Is there any evidence the coolant is being lost? Have you checked the level in the radiator and not just the overflow reservoir?

If you have and everything is good, allow the vehicle to reach operating temp. Open the hood and have a helper raise the engine RPM's. While that is being done, check to make sure there are no hoses collapsing. Specifically, focus on the heater hoses. Something is preventing coolant flow.

Also, here is a link you may find helpful:

https://www.2carpros.com/articles/car-heater-not-working

Try that and let me know what you find or if you have other questions.

Take care and God Bless,

Joe

Hi Joe, there is no evidence of coolant being lost. I cannot check the coolant in the radiator. The coolant goes through the reservoir into the radiator. Radiator has no cap to check it.the coolant level is okay in the reservoir.i am going to change all the hoses . The car is 29 years old . I will see what happens..

Hi,

If the hoses are original, that is a good idea. I'm curious if something is collapsing when the engine RPM's increase and the coolant flow increases. The idea that the engine temperature is normal and steady should keep the heat warm.

Let me know what you find or if you have other questions.

Take care,
Joe

Hello Joe. Thank you for the information. I see can i locate these hoses. Will let you know what happens. Take care, Wes

Sounds good. Let me know what you find.

Take care,

Joe