Some time ago, my heater started working intermittently. It would blow hot for a few minutes, then cool off. Now, it will not heat at all - it just blows cold air (Heat, defrost, etc..). Strangely enough, this only happens when it's cold outside. If it is warm, the heater will blow hot air. Any ideas? Thanks

 

Hi Tom, soon both of us will be whisked to a new Forum called HVAC by way of magical moderation.

At the upper left you will find this button
Click it and enter:
'Heater' as a search word
Change the search to 'Titles Only'
Change the Forum to 'HVAC'

There are 53 threads covering just about all the possible causes of your heater problem.

This will allow you find the answer right away rather than wait for the correct response to be repeated. Everyone is helpful here but, it could take days to get the right response and I know it's cold out.

Good Luck.

 

Have you checked your coolant level? And by that I mean at the rad, not the overflow jug.

Not to sound like an a$$, but sometimes you need to rule out the little things first.

 

Two things, first check the thermostat. If it's stuck open that will cause your problem. Second, check the coolant level AND mix to make sure it's 50/50. If the concentration gets out of whack, (too much coolant) Then it becomes less efficient at transfering heat. Antifreeze/coolant by nature isn't good at absorbing or giving off heat on it's own. That's why it needs water to work, the water is what absorbs the heat from the engine and releases it through the heater core. the coolant is what raises the boiling point of the water and prevents damage to the system. Your mix shouldn't be higher then 60% antifreeze/coolant.

BTW when it's warm outside the heat you do get is enough for you to notice it. It's only when it cools down that you don't feel enough heat.

 

THanks J 150. It was the coolant level at least i hope. My resorvoir was bone dry. So i filled, ran the truck a minute. FIlled it again..... I started the truck up and ran the heater but it was cold. I drove it again this morning however, and the heater started working. It was fairly warm today, so i'm not positive it's fixed, but it seems promising. Supposed to get cold tomorrow, so i'll know for sure then.

THanks