I HAVE A 02 CHEVY BLAZER HEATER ONLY BLOWS COLD AIR NO HEAT.I have replaced waterpump,thermostat,had radiator rotted out and flushed heater core.I noticed neither of the heater hoses where getting hot.I checked to see if the hoses where stoped up they where not.I even changed the thermostate again in case I got a bad one.Still no heat !HELP

Blocked air intake to system?

is there a chance that one of your heater hoses are clogged? or where they connect to the engine are clogged still? sounds like a clogged system. Cracked heater housing? Outside air bypassing the heater coil while driving?

Heat and air actuator
This could be the problem, in center under the dash.

Air Temperature Control Blend Door Failure No Heat or no AC (dependes on where door sticks)

In all modern cars there is a tiny DC electric motor driven gear drive that moves a plastic door that blends heated and cooled air from the AC and the heater core, this is called (interestedly enough) the air temperature control blend door actuator. The motor that moves this door fails because the door starts sticking from warping, most common complaint is no heat but it can be no AC as well. To replace these parts (blend door and blend door actuator) you must remove the entire dash from the car. Always have this problem confirmed by a dealer or qualified repair shop as it is a very expensive repair.

Other causes of no heat in the cabin are engine thermostats that are stuck open (engine runs cold) or air bubbles in the cooling system.

Try flushing or blowing high pressure air through the heater core lines. its sludge build up and need to be flushed through heater core only. check antifreeze fluid level. only put in straight antifreeze, do not mix. most people do not know what mixture should be, so be safe and add straight, it will not hurt it, i run 100% straight antifreeze and never had a problem or worry about it ever freezing and cracking my block, heads or radiator cracking.

Regarding this types of problem,i suggest you to go through this help links.Click the link below to go through the procedure and troubleshoot the problem :----

HOW TO REPLACE AN UPPER RADIATOR HOSE

http://schematicsdiagram.blogspot.com/2011/07/how-to-replace-upper-radiator-hose.html

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HOW TO REPLACE A LOWER RADIATOR HOSEhttp://schematicsdiagram.blogspot.com/2011/07/how-to-replace-lower-radiator-hose.html
----------How to Flush Heater Core?http://schematicsdiagram.blogspot.com/2011/12/how-to-flush-heater-core.html
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For heater core replacing procedure. I suggest you to go through this related help links.Its all complete step by step procedure: ----How to replace heater core for All car models?

Click the link below: ---

http://technoanswers.blogspot.com/2011/11/how-to-replace-heater-core-for-all-car.html

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How to Flush Heater Core?

http://schematicsdiagram.blogspot.com/2011/12/how-to-flush-heater-core.html

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How to Remove Heater Core ?

http://howtobyme.blogspot.com/2011/12/how-to-remove-heater-core-on-2008-honda.html
Heater Core Replacement?

http://howtobyme.blogspot.com/2011/12/honda-heater-core-replacement.html

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To replace heater core?http://technoanswers.blogspot.in/2012/02/how-to-replace-heater-core-on.html------

How to replace heater core?http://technoanswers.blogspot.in/2012/02/how-to-replace-heater-core-on_10.html
How to replace heater core on Buick Regal?

http://howtobyme.blogspot.in/2012/02/how-to-replace-heater-core-on-buick.html
----------This will help.Thanks.

Check the blend door actuator. Not sure where it is but usually right of center on the heater box, near the core. Looks like the picture below. Maybe you can trace the wires from the control panel. These actuators have a tendency to strip their gears--you may even hear it clicking as it tries to rotate the door. If not, plug it back in after you take it off to see if it will actuate. If the actuator turns, doublecheck the door to see if you can rotate it by hand. If the door is jammed, you may have to pull the whole box out to repair it. Let us know if you have more questions.

both hoses is hot signifies thatcoolant circulation is just fine check the blend door actuator it might be stuck.pan the heater temp controller from hot to cold do you feel any change in temp of the air from the blower?if you dont feel any change check the blend door actuator

I think you are on top of your problem,,you dont need any one elses advice.
Complete rebuild of the cooling and heating system,, simple.

what about electric system, is it connected could me a loose wire that disconnected on ur heater, check on that