'06 3500 diesel, while driving the heater was blowing warm air but suddenly started blowing cold air for about 1 minute then warm again by itself. Next day it would nlt blow warm air at all. Coolant level is good.

Low coolant, if there is an air pocket in the engine it will make it to the heater core. Once there , the air coming out is cold/cool. Once the coolant fills the heater core, it gets hot. If the coolant is fine hot or cold, then have the HVAC system scanned.

heater blows cold air idle chrysler 300 Questions & Answers ...

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Find solutions to your heater blows cold air idle chrysler 300 question. ... blow warmair for a few mins then back to luke warm. i replaced thermostat ... HEAT BLOWSCOLD AIR WHEN IDLING ONLY GETS HOT WHEN START DRIVING ... About 15 minutes after driving the diver side vents start blowing straight cold air but the ...

Heater only works when pressing the gas? - DoItYourself.com ...

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Nov 3, 2011 - When I press the gas, the air from the vents is nice and hot. .... So am Idriving a car with a ton of problems, or could the power steering ... Just anotherquestion, when warmed up does the engine temperature ... When the heater is on and I'm not pressing the gas pedal, luke warm air blows from the vents.

Heater blows cool air when stopped and warm air while ...

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RedditFeb 12, 2014 - Heater blows cool air when stopped and warm air while driving 2008 Kia Spectra (self. ... just fine but appears to blow cool air when I was stopped at a stoplight. ... My temp gauge would also be pegged high when at idle / low RPM. ...thermostat only blocks coolant going to the radiator, and the heater core, ...Missing: 300m ‎luke

Why is My Car AC Blowing Hot Air? - BlueDevil Products

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check and make sure the radiator is full of antifreeze take off the radiator cap and top off the radiator then take your hand and cover the hole where the cap goes and squeeze the top radiator hose a few times to help it go down that way if there is a air pocket somewhere it will help push it out when you thank your done top off again and replace the cap and try

The water pump impeller has come adrift from the drive shaft ,one is plastic and and the other metal and they come apart causing this sort of problem

U could be run on eco a/c where the engine is using the power until it has extra to spare. Warm at start could be simlarly that there is now cold air yet and has to "make" cold air to distribute when ready. See if u can find a setting for reg use. cheers, ps eco saves dollars/euros.

your ac compressor is freezing up try not putting it on cold all the way. put thermostat towards the red jus a lil but still on the cold side to see if that helps

It is most probably the problem with blend door or blend door actuator. But just in case I would suggest to follow the entire procedure:

First you have to identify what causes the problem.
To do this you have to:
1) When engine is cold check the level of coolant. If it is low fill it up.
2) Start engine and check if engine reaches regular temperature. If your engine is not heated enough it means your thermostat does not work properly and should be replaced
3) If engine temperature is normal, then check the temperature of pipes that go to/from heater core. These pipes are located up the fire wall (easier access is from the passenger side). If pipe/pipes are cold (even engine is warm) it means you heater core is plugged and should be flushed. Keep in mind, flushing the whole cooling system is different from flushing heater core.
4) If pipe/pipes are hot/warm, turn off the fan, switch controller to the hot position, wait for 3-4 minutes and turn on the fan. Note if the cold air blows first or warm air blows first but it cools down in 5-10 seconds. If the air blows cold than it is most probably the problem with blend door or blend door actuator.
5) If air blows warm first and then cools down, then while running engine and remaining the transmission in PARKING position, press on the gas pedal until your engine reaches 3,000 RPM. Check if your heater blows warm/hot air. If it does, then your water pump does not work properly and should be replaced. If the air still cold, I would suggest flushing the heater core.

sounds like you have a leak in the system and have air that has entered into the system.
best to have it serviced by a shop, the system will need to be inspected to find the leak and then evacuated. part replaced and refilled.
leak detector will be okay

Do NOT use the cans of refrigerant with sealer in it.
and do not let the shop put a sealer in it, in the long run this will cost you the replacement of the whole a/c system.

check coolant level ,must be low ,chck for coolant loss

water pump