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90 Suburban ~ Heater

Discussion in 'The Garage' started by Melitta, Dec 16, 2004.

  1. Melitta

    Melitta Registered Member

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    Having trouble with the heater in a 90 Suburban. While driving heater switches back and forth from blowing warm air and cool air. If stopped at a light it will only blow cool air. Do not have rear heat (although wish we did) and just replaced the blower wheel (squirrel cage). Although it still doesn't seem to blow air (a/c or heater) as much as it should. Also, the vent closest to the driver, the one above the radio doesn't blow much air ~ almost none at all actually, but the one by the driver leg blows fine. Can anyone tell me what to look for? Thinking maybe the heater coil, but would that switch from heat to cool like ours is doing? And would it stop blowing warm air altogether when the vehicle is stopped? Also, notice I say warm air. Heater doesn't blow hot, only a luke warm. Thanks to anyone who can offer advice!
     
  2. K5HIGH

    K5HIGH 1/2 ton status

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    iTS A HEATER CORE NOT COIL BUT IF IT IS WAS BAD U WOULD PROBLY SMELL ANTIFREEZE AND YOUR WINDOWS WOULD BE STEAMED UP. IF ON DEFROST DOES IT BLOW HIGH WHEN TURNED ON HIGH?
     
  3. Melitta

    Melitta Registered Member

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    iTS A HEATER CORE NOT COIL BUT IF IT IS WAS BAD U WOULD PROBLY SMELL ANTIFREEZE AND YOUR WINDOWS WOULD BE STEAMED UP. IF ON DEFROST DOES IT BLOW HIGH WHEN TURNED ON HIGH?


    No, it doesn't blow full blast on any settings. Set on high the air feels like it only blows at a medium setting. Windows aren't steamed up and don't smell antifreeze either.
     
  4. K5HIGH

    K5HIGH 1/2 ton status

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    BLOWER MOTOR MIGHT BE BAD BUT THAT WONT CAUSE IT TO BLOW COOL. START WITH THE SIMPLE STUFF CHK COOLANT LEVEL MAKE SURE THERE ARE NO LEAKS IN SYSTEM. CHEK YOUR CAP AND OVERFLOW BOTTLE.THEN FORM THERE MAYBE THERMASTAT. ANYBODY ELSE?
     
  5. 88sub4x4

    88sub4x4 1/2 ton status

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    Check coolant level first, then make sure the vacuum lines are not cracked or broken, especially the ones under the hood. There is also a plastic piece on the mode door that breadks sometimes, and will make the air distribution go to different places then you set it to. I would check the coolant (and T-stat)and vacuum lines first though. If they are all OK I can explain where to check for the broken door piece, but check those first.
     
  6. Melitta

    Melitta Registered Member

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    Will do. Thanks for at least giving us a place to start. We bought the Suburban used a year ago, so we are new to the in's and out's of what makes the Suburban tick. The low blowing air flow isn't that big of a deal with the A/C cause we have the rear one that will blow you away. But, we don't have rear heat and the kids are getting cold in the back with the combination of low air flow and the heater switching from warm to cool air. You know come to think of it, the front A/C does the same thing...it blows cold while the vehicle is moving, but when stopped the air starts to warm up some. Not a good thing in Texas heat!
     
  7. Melitta

    Melitta Registered Member

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    Thanks! As you can probably tell I am a female and have no clue how to fix a vehicle! I am learning though! I find the suggestions on how to fix the vehicle and hubby does the work, with me right there in the way of course! I will relay this info. on to the hubby and let him do his thing. He had an idea of what needed to be checked, but always nice to have other opinions to make sure you are on the right track. Thanks so much and you will be hearing from me again I'm sure.:grin:
     
  8. 88sub4x4

    88sub4x4 1/2 ton status

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    Any vehicle will do this a little because there is less air flow through the condenser, but it is even more noticeable on older vehicles without electric cooling fans. Let us know how you make out with the heat.
     
  9. K5HIGH

    K5HIGH 1/2 ton status

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    GOOD LUCK:thumb:
     
  10. tx_sub

    tx_sub 1/2 ton status

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    you said the blower doesn't work on the highest setting, its probably the blower relay. i replaced mine this past summer. the relay is on the ac box under the hood. can't find the part number now, but i got it a napa. good luck.
     
  11. Melitta

    Melitta Registered Member

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    Well, we checked out the coolant and it was low. That made all the difference in the world! The heater is now blowing HOT again! Still need to figure out what is wrong with the direction all this air is blowing. Most of the air is blowing at the feet. Yet, hubby had me moving the switch that should change it from bi-level, defrost ect. and said he could feel it moving (his hand was under the dash) when I moved the switch but the air was staying at the feet and no defrost at all. Would that still be the relay switch as someone suggested or do we need to be looking somewhere else?
     
  12. diesel4me

    diesel4me 1 ton status Premium Member

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    warm feet--cold hands!

    The heater controls are run by vacuum from the engine if it has A/C--all it takes is one hose either the main one that goes to the engine,or one of the many under the dash to disconnect and it wont go from heat to cool,or"defrost" or "bi-level"--there are vacuum canisters that do the actual moving of the levers that divert the airflow to the various places,if one of them fail it wont re-direct the air also--could be the heater control itself on the dash too,all those hoses meet there,thats where all the "switching" takes place--most times its a disconnected hose though..you might hear a hissing noise while the engine is running coming from a disconnected hose under the dash or hood...there is usually a vacuum operated "hot water valve" in one of the heater hoses that will shut the hot water off to the heater core in the summer when the A/C is on--if this valve fails,or doesnt get vacuum,it wont let the heater core get any hot water--thus no heat--you said filling your radiator made the heat work again,so this probably isnt the problem in your case....

    The trucks without A/C use manual cables from the heater controls to the various doors and levers to control the airflow--a disconnected cable,or a broken one,will prevent you from getting heat or defrost--I think you said your truck had A/C,so this doesnt apply to yours....:crazy:
     

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