No Heat in 04 Chevy Trailblazer :-(

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  #1  
Old 04-24-12, 12:51 AM
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Join Date: Apr 2012
Location: England
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No Heat in 04 Chevy Trailblazer :-(

Looking for any help I can get... Stationed in England with the Air Force and have my US Spec Trailblazer. Hard to find someone who knows what they're doing to work on it... Heat stopped working after we had about 2 warm weeks and I didn't use it. Now I'm getting nothing but cold air and I need the heat again. Any suggestions on things I should check? Not very mechanically savvy, but hoping I can figure out the problem rather than take it somewhere and have them charge me some ridiculous rates (since everything is in pounds and so much more expensive than the dollar).
 
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Old 04-24-12, 04:31 AM
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Couple of possibilities. You didn't mention mileage, but these mostly apply to any heat problem, in no particular order:

1. Clogged heater core. More likely the older/higher mileage the vehicle. Can check this by feeling the two heater hoses, both should be hot; if not it may be a circulation problem/clog.
2. Related to #1 is an air bubble/pocket in the system. This sometimes happens after the cooling system is opened for service/repair, i.e. water pump replacement, new radiator, thermostat, etc.
3. If the system has a mechanical metering valve for the hot water, it may have failed or the cable has come loose. Not all vehicles have a valve, more on that in a minute. If it has a valve it should be easy to spot somewhere in one of the heater hoses between engine and firewall. Check for operation when the lever on the control panel is moved.
4. Failure of the blend-door or it's actuating mechanism on vehicles that do not use a mechanical valve to regulate the heat. On these vehicles, the heater core gets hot water all the time and the temp coming out of the vents is regulated by the blend door's position which allows more or less cool air to mix with the heater core output. You will need to hunt for the blend door mechanism under the dash where the ducting is; the actuator may be mechanical or vacuum operated. Often the vacuum-operated ones stop working because of a vacuum leak.

My older brother did some time in the USAF in your neck of the woods, but he was the black sheep of the family . [Tow Guy, USMC ]
 
  #3  
Old 04-24-12, 06:53 PM
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Everything that the_tow_guy said but without knowing the maintenance on your truck I suggest you also get a complete coolant flush and fill if not already done in the past 3 or 4 years. Do you know if it ever has been done? Also check to make sure that your coolant level is topped up in the reservoir as a first step also. Is the engine temperature reading normal on the instrument cluster?
 
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