Question about 2001 Chevrolet Suburban
Once the vehicle warms up the engine operating temp, the defrost air and the air coming from the vents are all at a satisfactory temperature. When driving in the highway & slowing down or when driving in town & coming to a complete stop, the hot air begins to cool down until the vehicle is moving again. When the car begins to move, the temperature of the air begins to warm back up? I've had this happen with a van I drove that had a diesel engine. This suburban is a gasoline engine & I've never noticed this before. What would cause this?
Sounds like a possible plugged heater core, restricting the flow of coolant. those require a special tool to remove, quick disconnect, just remove both hose from the heater core and back flush the heater core with a garden hose, NOTICE DO NOT DO THIS WHILE HOT IT WILL BURN YOU, this can make a mess, flush it both ways untill it flows clean and with even pressure, then refill the coolant and road test the vehicle to see if is changed.
Posted on Jan 15, 2013
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Posted on Jan 02, 2017
First check and make sure you have enough coolant. If so your thermostat needs to be replaced it is stuck open. you can find online repair manuals at autozone.com for free.
Posted on Mar 05, 2009
when your car is in defrost it has an ac cycling it removes the moisture then sends the air over the heater core depending on how warm you set it you can feel warm or cold but the ac is always cycling...ridding the moisture...you need a good ac tech it will be okay...its just expensive going into the heater core if needed...!
Posted on May 07, 2009
Did you hear a little rythmic squeaking noise under the dash by the driver's right knee? Is the noise now gone? There is a little oscillating air flow gate there that often goes bad...I can't remember the name of the part, for the life of me, but the dealer has them.
Posted on Jul 03, 2009
The car uses the same freon in the front as it does in the rear. If the rear a/c is working, you either have a plugged evaporator in the front unit, or perhaps a bad heater switch. Try switching the heater to hot and see if it blows even warmer air from the front vents. If so, the heater switch is working and then it sounds like a plugged evaporator or maybe a plugged orifice tube. That is a good place to start looking. Hope this helps.
Posted on Jul 07, 2009
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Keep this principle in mind: Heat, flows INTO cold... When you hold an ice cube in your hand, your hand gets cold because the heat from your hand is flowing INTO the clod ice cube, NOT because the cold is flowing into your hand.
On this particular vehicle (like many modern vehicles), hot water from the engine flows through the heater core at all times, even when you have the A/C on or when you have nothing (A/C, heat or vent) on. The system uses a door that closes down over the air opening to the heater core to keep you from feeling warm/hot air when it is not desired. The reason(s) you feel that the vent air is warm even when the outside temperature is somewhat cool is/could be caused by the following:
First, although as mentioned above, the heater core is restricted from receiving air when you are not commanding heat by the control panel, the heater core ultimately ends up as warm as the engine temperature. This is generally somewhere around 200 degrees F. Because all the air coming out of your vent(s) must pass over the door that restricts air over the heater core, and because the heater core gets so hot, some of that heat is picked up by air passing over the hot door even though it is closed.
Second, the door that restricts airflow from passing over the heater core has a seal around it. After a period of time this rubber (or usually felt) seal deteriorates, allowing some air to actually pass over the heater core. Since the core is hot all the time, some of the air gets heat loaded, producing warmed air.
Third, the door is operated by (in the case of your vehicle) an electric motor which responds gradually/proportionately to the setting you select on the temperature dial. If the motor gets out of calibration (can happen from time to time), if the control head has a 'glitch' and sends an incorrect signal (chronically, usually), or if the electric motor (called an actuator and contains its own little electronic 'brain') becomes faulty, the door may not be closing completely. This symptom can also be caused by a problem with the door itself, where the door gets stuck due to warping of the plastic case, a foreign object preventing it from closing (usually a pen or toy dropped into a vent or defrost opening), or a broken or cracked door hinge.
Last, the vent intake opening, where the 'fresh' air comes into the car on the 'vent' setting, is located just below the windshield on the passenger side. This opening receives its air directly off of the sun-baked, engine-heated hood and because of this the air is never as cool as outside air even on a cooler night.
I hope this answers your question. Many domestic vehicle manufacturers have begun installing heater control valves on their vehicles once again as they nearly all used to have. Note that the fix for most everything I have mentioned here requires removal of the dash of the vehicle or replacement of the control head and therefore is in many cases not worth the investment if it is not an extreme problem (for example, unless the system is stuck on full heat in the middle of summer. Additionally, remember that, if you so desire, manual shutoff valves can be placed in the heater hose lines (please consult a qualified mechanic as water from a vehicle can and will scald and burn you!), allowing you to manually shut off the flow of water into the heater core, thus reducing some of the heat (Readers note that certain foreign vehicles REQUIRE water flow through the heater core at all times for engine cooling and are not candidates for this procedure!).
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