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1999 Silverado no heat!

This is a discussion on 1999 Silverado no heat! within the Technical / Maintenance forums, part of the General Discussion category; I have a 1999 5.3 Silverado Z71 blowing nothing but cold air. It will not switch to warm or hot ...

  1. #1
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    1999 Silverado no heat!


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    I have a 1999 5.3 Silverado Z71 blowing nothing but cold air. It will not switch to warm or hot air. I have replaced the thermostat-flushed the system and still have this issue... Looking for some help on this. Has anyone had this problem as well..

    Thanks
    Don

  2. #2
    Registered User 99silveradoqc's Avatar
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    Re: 1999 Silverado no heat!

    Same thing happened on my 99. It could be the temp valve actuator (Blend door Actuator). When you turn your knob from cool to warm can you hear any door or flap opening or closing under your dash centered right above your tranny hump. Mine was stuck on the heat side and I went 2 years with no A/C due to thinking I was going to have some expensive fix. After figuring out that it was the blend door I ordered one from Rock Auto and had it installed in less then 10 minutes. Could be a possibility... Hope it helps!

  3. #3
    Not Really Bob
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    Re: 1999 Silverado no heat!

    Either the blend door as mentioned above or the heater core is clogged up and needs back-flushed.
    99 Silverado ECSB 4X4, LQ4, Patriot Stg. 2 243's w/ 59cc chambers, TR224-112, Pacesetter LT's, Nelson tune, FLT Lvl 5.5, PI 3400, UD pulley, 160* t-stat, E-fans, 6'' Fabtech lift, 3'' body lift, 37'' XTerrains, 4.56's, 4'' shackle flip 13.3 @ 99mph on 37's or 13.0 @ 101mph on 31's

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    Re: 1999 Silverado no heat!

    had the same problem and it was the blend door actuator
    and thermostat changed both and works great



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    Re: 1999 Silverado no heat!

    where is the blend door actuator? im having the same exact problem and dont hear the door when i turn knobs.
    is it kinda like a fuse you relace?

  6. #6
    Registered User 99silveradoqc's Avatar
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    Re: 1999 Silverado no heat!

    Blend door is directly below your radio and about 2 inches above the top of your tranny hump. It's about a four inch diameter piece held on with three screws that are so close to the floor it's kind of tricky to get a socket on them to remove them.

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    Re: 1999 Silverado no heat!

    ok and when i go to the parts shop im asking for the lower one right?

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    Registered User Tweaks's Avatar
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    Re: 1999 Silverado no heat!

    Don't forget to inspect/clean/replace if necessary your cabin air filters while you are at it. Lots of folks don't even know our trucks have those and they can prevent warm air from entering the cab if they are packed with years of junk.
    00 RCSB Z71/JBA cat-back/Z71 Tahoe valance/EBC slotted&drilled rotors with SS lines & SS braided hoses/Edelbrock headers/BB tune/6000k HID low beam & fog lamps/Auto-headlight disable mod(nice)/Vette servo/LT1 E-fans/LED gauge cluster/Titan 18" wheels/Rollpan/Belltech rear sway bar/2-4 drop

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    Formerly Old77 07Burb's Avatar
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    Re: 1999 Silverado no heat!

    I haven't read all the posts but if you haven't done it yet check the heater core as your hoses could be at least partially blocked if not fully blocked. Either that or your heater core could need replaced.

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    Re: 1999 Silverado no heat!

    Quote Originally Posted by Tweaks View Post
    Don't forget to inspect/clean/replace if necessary your cabin air filters while you are at it. Lots of folks don't even know our trucks have those and they can prevent warm air from entering the cab if they are packed with years of junk.
    What are the cabin air filters and where are they on our trucks?
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    Re: 1999 Silverado no heat!

    update..........Blend door Actuator was the issue. Also replaced cabin filters as well and thermostat and flushed heater core. works like a champ.

    Thanks for the feedback everyone
    Don

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    Re: 1999 Silverado no heat!

    is there a diagram of how the actuator comes out? or pics?

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    Re: 1999 Silverado no heat!

    ok update on my situation....
    i removed the blend door accuator and indeed it is malfunctioning, so i have a new one on order,
    i then turned my truck on and blasted the heater, and moved the air door by hand and it does not seem to change what is coming out, JUST LUKE WARM AT BEST MOSTLY ON COLDER SIDE
    so how do i reverse flush the heater core? and what else could the problem be?

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    Re: 1999 Silverado no heat!

    any up dates?
    00 1500 Z71 ecsb 225,000 miles still runnin strong

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    Re: 1999 Silverado no heat!

    ok i have now replaced the blend door acuator, and the t-stat.
    STILL NO HEAT WTF!!!!!!
    i swear i should defect to fords

  16. #16
    Formerly Old77 07Burb's Avatar
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    Re: 1999 Silverado no heat!

    Idea....go to Best Buy, buy a converter that'll plug into your cig lighter and has a plug in for cords on the other end. Then go buy a space heater to plug into the converter. Less money, more heater, no more headache,.....problem solved

  17. #17
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    Re: 1999 Silverado no heat!

    the funny thing is, i have done this before in my old blazer that had no heat.

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    Re: 1999 Silverado no heat!

    UPDATE!!!!!!!!!!!!!!!!!!!!!!!!

    ok so its been getting colder and i have a daughter to think about so i tried my last resort

    FLUSH THE HEATER CORE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! i flushed the core 4-6 times both forward and backward until it was flowing good. be careful cause the core adatpers are very brittle and one of mine literally fell off
    go to your local parts store and get one it will be all black and are only 9 bucks, the dealer wants 45. now there is a whote fitting and a black one but there is no difference as i put a black one on and works perfect.....
    HINT: put alittle tranny fluid or oil or any lubricating agent and rub it in side the fitting before you slide it on, and it will go on alot easier!!!!!!!!!!!!!!!!

  19. #19
    The MEAN Helper 99SilveradoNBS's Avatar
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    Re: 1999 Silverado no heat!

    Bumping this thread.

    I have a 99 aswell The blend door motor died so I pulled it out and I can turn the door on the truck by hand to switch from AC to Heat. But recently my heat hasn't been all that warm I have to reach normal operation temp (just below 210) for it to get somewhat warm How do you flush the heater core? Where is it? also thermostat maybe the problem?

  20. #20
    I love chrome SoSoFLY's Avatar
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    Re: 1999 Silverado no heat!

    Heater core is in your dash, passengers feet. To flush it, you will see under the hood there is 2 garden hose sized hoses attached to the firewall. Undo these, and pour some CLR down the top hose and kink the bottom one. Wait 15 min the flush all the garbage out with a garden hose till its clear. Then hook em back onto the engine, top off coolant lost and away you go.
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