heater blowing cold??

[drumzz]

Okay, things have been running fine lately..i take the truck out tonight to pick my son up from work and my heater is blowing ice cold all of a sudden?? any ideas as to what might have happened?? i have done a few things under the hood in the last few days but nothing with the heater.. thanxx in advance guys

[72BahamaBlue]

Low coolant might be the cause. Check to see if the valve connected to the heat control cable is working and open. Park on an incline nose up, try to purge any air out of radiator. Engine off, try squeezing the top rad. hose a few times, watch for bubbles in the rad.cap opening...fill radiator, run engine and test heater. Might take a couple of tries to get all the air out. An easy and free first step.

[drumzz]

coolant level fine?? ill check the valve out tomorrow thanks man!!

[chad30021]

I had that same problem not to long ago. It turned out to be the heater control valve just like 72 bahamablue said. It was moving open and closed from the looks of it but I took it off and the shutoff was rusted through!

[drumzz]

ok today was a different story..lost about a gallon of coolant { still have no clue where it went?? not in the passenger floorboard } thermostat is good, heater control valve is good?? did i just lose a heater core?? im at a lose

[chad30021]

If you lost a gallon of coolant was it while you were driving or the truck was just sitting? If it was while you were driving there are multiple places that the coolant could have leaked out of for instance, the plug on the bottom driver side of the radiator, mine leaked from there a while back. That is just a start of course, If your heater core went out it would definently have antifreze dripping into the cab from it. A simple reason that it may be blowing cold air though, just a thought, your core may be clogged up. I think the best way to tell is just to pull it off and have a look at it. I know its propbably something you already thought of but hey, whats another opinion

[basketcase0302]

there's a lot of places the coolant can be leaking from, replacing your radiator cap is usually a good start here IMO. Look at all your hose connections, (after the engine has been cycled through a normal run cycle). And if there's not a puddle in the PS floor board, I'd guess the core is ok. Just a FYI that you might want to also check your airflow. Is the blower motor working-and on high speed, and is the airflow to the core itself clear-remove the fresh air ducting to verify (usually plugged with leaves).
Hope it helps!

[72BahamaBlue]

Adding a coolant overflow resevoir will help keep the level up. As others mentioned, many ways for it to escape. If loss is slow and no leaks, or smell of coolant in the cab, might get away with an occasional topping off.

[70_F100]

Low coolant is a prime reason for a heater to blow cold.

Any chance you've drained the cooling system lately (or possibly even since last winter)? If you got an air pocket somewhere, it may have purged itself and that's why the coolant is low.

[Madman]

Check the oil and see if it is frothy.....indicates a leak into the oil system