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  1. #21
    Jr. Engineer JTWard's Avatar
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    Ya know GMANs95, I'll bet you have the doors in the heater assembly are either broken of worn out. Their made out of plastic and often the cable that controls a particular door snaps off. But you need to drop the heater assembly out to open it up and see what not happening when you want it too !

  2. #22

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    I'am starting to agree with @JTWard, it is starting to sound like a problem in the HVAC unit. Over the years, we have had 3 different methods to move the temp doors. We have used cables, we have used vacuum motors and the new trucks use an electric motor to operate the doors. I don't know what is in yours.

    As for the blower speed control, it is most likely the speed control resister. However, in a lot of the designs, the manual unit has 2 fuses to operate the blower. One fuse is used for the high speed position and an other fuse is used for all other speeds. Check the HVAC fuses, if they are all good, the problem is probably the resistor.
    Ray

    '09 Avalanche LTZ - Black
    '05 Envoy XL (sold)

  3. #23
    Jr. Engineer JTWard's Avatar
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    Hay Ray, Yeah, I think it's a rats nest of hoses on GMANs95 that's giving him the cool air but hot hoses. My 1990 uses vacuum lines to run and route the opening & closing of the doors. From his tale, there's been work done under the dash, and it wasn't done by a professional. The reason I mention it, is I just had a new heater core put in my Silverado. The old one wasn't leaking, but I've put a ton of work hunting the exact original carpet set that came in my truck from the factory, and I put down dense soundproofing and I did a real tight job of sealing every corner and curve in the floor with the seats out, I didn't want to chance a 23 year old leaking heater core destroying all my work. But on another subject, what a "Avalanche" like ? I am looking kinda for a replacement of addition to my stable. The LTZ is the top of the line, all bells and whistles and options right. The Avalanche uses a Uni-body /sub frame arrangement right? The Silverado 1500 is like my truck a body mounted on a rigid frame. I read that the Uni-body/Sub frame is a stronger platform. Yours is pretty new, what's it like, Gas Mileage, convenience handling ? What's the Avalanche like ?

  4. #24

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    Quote Originally Posted by JTWard View Post
    what a "Avalanche" like ? I am looking kinda for a replacement of addition to my stable. The LTZ is the top of the line, all bells and whistles and options right. The Avalanche uses a Uni-body /sub frame arrangement right? The Silverado 1500 is like my truck a body mounted on a rigid frame. I read that the Uni-body/Sub frame is a stronger platform. Yours is pretty new, what's it like, Gas Mileage, convenience handling ? What's the Avalanche like ?
    Haha, that sounds like the same excitement most of us felt when we first saw you aviator and thought it was you.

    Thanks for the kind words, the Av uses the Suburban's full frame. From the back of the front seat forward, it's the Burb. What I like about the Av is the mid-gate. I can leave the bed's covers on, drop the gate and have inside dry storage for sheets of plywood and sheetrock (I own some apartments and I'm always renovating something). I've used SUVs and I always get the inside dirty, and I hate dirt on the inside. I'm a Shriner and I can remove the bed covers and get my parade bike into the bed and close the tail-gate, it's pretty versatile. The truck has a 5.3 with a 6 speed and it will give great mileage. I tend to drive a little fast, but I can get 20 mpg most of the time. Yeah, it's the LTZ, has everything except the upgraded wheels. I didn't buy it new, it was a couple of years old. I didn't want a LTZ, I was looking for a work truck, I did want buckets and the console, but a bare bones LT would have worked. The LTZ sat on the lot all summer and fall, one morning the dealer had an ad in the paper with a number of vehicles going to the auction if they didn't sell. They had dropped the price by $10,000 so I grabbed it.

  5. #25
    Legend

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    1990 uses vacuum but not the 2000 on up models to control air temp. also no coolant valves.. heater core hot even with the AC on ...both hoses hot no heat then the TEMP DOOR is stuck in hot or cold position. can also be the electronic controller. the stepper motor is powered by 5 volts dc to position the temp door for the desired temp...

  6. #26

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    MMM.....that sounds exciting.

    I did manage to find out the the left hose (to water pump) is the hottest hose. The knobs on the enviro cluster don't seem to work very well either....

    It was 30 degrees this morning...that hot air sure woulda helped....lol.

    will probably drop it this weekend if it doesn't rain....

    Quote Originally Posted by JTWard View Post
    Ya know GMANs95, I'll bet you have the doors in the heater assembly are either broken of worn out. Their made out of plastic and often the cable that controls a particular door snaps off. But you need to drop the heater assembly out to open it up and see what not happening when you want it too !
    - - - Updated - - -

    I am sure there was as my son loves the flashy, but neglects the functional......but how much was him I don't know...could been the redneck that owned it before him....who knows. Either way its a project for me. I work in telecom and find this stuff a great stress reliever (sometimes)

    Quote Originally Posted by JTWard View Post
    Hay Ray, Yeah, I think it's a rats nest of hoses on GMANs95 that's giving him the cool air but hot hoses. My 1990 uses vacuum lines to run and route the opening & closing of the doors. From his tale, there's been work done under the dash, and it wasn't done by a professional. The reason I mention it, is I just had a new heater core put in my Silverado. The old one wasn't leaking, but I've put a ton of work hunting the exact original carpet set that came in my truck from the factory, and I put down dense soundproofing and I did a real tight job of sealing every corner and curve in the floor with the seats out, I didn't want to chance a 23 year old leaking heater core destroying all my work. But on another subject, what a "Avalanche" like ? I am looking kinda for a replacement of addition to my stable. The LTZ is the top of the line, all bells and whistles and options right. The Avalanche uses a Uni-body /sub frame arrangement right? The Silverado 1500 is like my truck a body mounted on a rigid frame. I read that the Uni-body/Sub frame is a stronger platform. Yours is pretty new, what's it like, Gas Mileage, convenience handling ? What's the Avalanche like ?

  7. #27
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    if both hoses are not hot then you have low flow thru the core.

  8. #28

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    Even with low flow...shouldn't I be getting some heat? I will probably flush it out just to say its done. So with that in mind which one is supply and which is return? Left one goes to water pump and right one goes to intake.

    Quote Originally Posted by j cat View Post
    if both hoses are not hot then you have low flow thru the core.

  9. #29

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    Quote Originally Posted by GMANs95 View Post
    Even with low flow...shouldn't I be getting some heat?.
    I would think you should. I think @JTWard may be on the right track with the temp door. @j cat said the 2000 and up uses electric doors, so yours must have vacuum motors to move the door. Look for a broken/rotted vacuum hose.

    If the engine is off, but the key is on, and you change the temperature control, can you hear the door move?

  10. #30

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    No nothing.
    Quote Originally Posted by RayVoy View Post
    I would think you should. I think @JTWard may be on the right track with the temp door. @j cat said the 2000 and up uses electric doors, so yours must have vacuum motors to move the door. Look for a broken/rotted vacuum hose.

    If the engine is off, but the key is on, and you change the temperature control, can you hear the door move?
    - - - Updated - - -

    This issue just took a back seat to my tranny taking a dump on the way home.........won't shift into 3rd or OD. Plenty of fluid and new filter......DOES IT EVER END!!!!!

    Quote Originally Posted by RayVoy View Post
    I would think you should. I think @JTWard may be on the right track with the temp door. @j cat said the 2000 and up uses electric doors, so yours must have vacuum motors to move the door. Look for a broken/rotted vacuum hose.

    If the engine is off, but the key is on, and you change the temperature control, can you hear the door move?

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