My 2008 Mustang heater blows cold air even when the engine has warmed up. However, after about 20 or so minutes, warm air will start coming through vents. Seems to happen after RPMs reach a certain speed. And if the car sits idling, will go back to blowing cold air. Help?
Hi Chris, sounds like your thermostat may be worn and not closing all the way which would cause your engine to run cool at times. If you have a temp gage it should tell you if the engine is actually warming up or not. If not I would replace the thermostat.
Testimonial: "Thanks for answering. The engine gauge will show the engine has warmed up; is this what you are talking about? Thanks"
SOURCE: Heater blows cold air when idle
Sounds like you may have a partially plugged heater core. You could flush this out separately, from flushing radiator & engine block. Diconnect heater hoses going to your heater core and clamp off, so not to loose coolant from engine. Now hook up separate hose to one side of heater core pipe and flush out with typical garden hose. Repeat procedure on both heater core inlets. Reconnect original heater hoses and test difference. You may have to add an additional litre of antifreeze. If this don't work i suggest changing heater core. Good luck.........Ron.
SOURCE: Heater blows cold air unless accelerating
See my posted question under 2001 Mercury Villager: "HEAT BLOWS COLD WHEN CAR IS IDLING" I got an answer from chuck943 about air pockets and it was very helpful.
SOURCE: heater on ford 2003 ford pick up blows cold air
on the evap box there is a control mtr that switches the hot cold door. these mtrs are prone to failure. the other problem that i have seen is that the door breakes in side the evap box and that means removing the box to replace the door . if i remeber correctly you may have to slide the dash back to gain assces to the control mtr to test it good luck
SOURCE: Heater on driver-side blows barely warm air other vents blow cold
the most probabale cause of this would be a disfunctional hear core if you replace your heater your heater will more than likley work the the way it's supposed to
SOURCE: Rear heater blows only cold air no matter what the
If this is equipped with a rear heater core it is probably plugged up and needs to be disassembled and cleaned out
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Thanks for responding. I took it this morning to a mechanic friend and found out we had NO WATER or COOLANT ! Yikes! He filled it up for me, and told me to bring it by occasionally so he can check to see if we have a leak somewhere. He couldn't find one this morning. It heats beautifully now. Thanks you again for your suggestions.
Thanks for the info Chris. I thought my radiator reservoir was full but found it only looked full because of the orange residue. I actually had to add over 1 gallon water and coolant. Wow! Heater works great now! :) I have a 2014 V6 and had same symptoms as you. With it getting cooler out here in Columbus, OH definitely will need the heater!
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