Intermittent heater not working?

Tiny
VASHONE77
  • MEMBER
  • 1998 FORD EXPEDITION
  • V8
  • 2WD
  • AUTOMATIC
  • 173,000 MILES
My heater will come on blowing hot for about 30 sec, then it turns cool. What could be the problem?
Friday, February 12th, 2010 AT 4:42 PM

1 Reply

Tiny
SQM
  • MECHANIC
  • 6,383 POSTS
Hello,

First check your coolant level. A low coolant can cause the heater to not function properly, as the coolant will not flow thru the heater core.

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

Another possibility is a stuck open thermostat. If the thermostat is stuck open then the engine will not reach the operating temperature and when that happens the heater will blow cool air.

https://www.2carpros.com/articles/how-an-engine-thermostat-works
https://www.2carpros.com/articles/replace-thermostat

I have attached diagrams for your reference.

Please let me know of any questions.
Thank you.
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Friday, August 27th, 2021 AT 9:12 PM

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