Help! No Heat!! - S-10 Forum
 
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post #1 of 33 Old 10-23-2007, 09:39 AM Thread Starter
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Help! No Heat!!

Its getting cold out and my truck isnt making warm air! I changed the thermostat. When I turn the fan to the off position and wait, then turn it on, I get a small blast of warmth, but then turns cold again.

What gives??

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post #2 of 33 Old 10-23-2007, 10:33 PM
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Re: Help! No Heat!!

love your avy. my trucks ac/heater doesnt work all that well either, only the bottom vents blow. odd? and this morning on heat and tep all the way up there was cold air comming out the vents? sorry if it seems like im jacking your thread, im having a similar problem.
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post #3 of 33 Old 10-23-2007, 11:02 PM
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Re: Help! No Heat!!

check your coolant level

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post #4 of 33 Old 10-23-2007, 11:09 PM
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Re: Help! No Heat!!

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Originally Posted by AceHaag View Post
check your coolant level
X2. and if you dont get heat but only thru the floorvent check the actuator that opens the vent. its hooked to the floorvent
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post #5 of 33 Old 10-23-2007, 11:17 PM
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Re: Help! No Heat!!


after I changed my water pump my car blew warm air... What is your temp gauge at? If your level is low and it was just up check those leaking places on your water pump. *yes I'm stupid and forgot what they are called
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post #6 of 33 Old 10-24-2007, 05:19 AM
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Re: Help! No Heat!!

Probably your heater core, my son's 88 s-blazer was same. wouldnt hardly give heat, new thermostat, flushed no good, changed heater core now roasts him out.
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post #7 of 33 Old 10-24-2007, 07:35 PM
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Re: Help! No Heat!!

If the previous owner, at some point and for some idiotic reason, decided that using hard tap water as a substitute for clean water, like my previous owner... I wouldn't be surprised if your entire heating/cooling system is covered in calcium deposits. It's a general rule of thumb that when you but a new dime, you buy a huge list of parts that, whether you think it needs it or not, MUST be replaced....

When you do the job, buy new hoses, both heater and rad hoses, check the radiator for deposits but avoid using stop leak if you find drips..

LMCtruck.com has most of the parts you need for electronics/vacuum control of the entire hvac system, as well as vents, but I'm not sure about the ducts and diverters..

If all else fails, JC Whitneys sells those little 12v cab heaters, though I'm sure the ladies will LOVE that idea:-p

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post #8 of 33 Old 10-24-2007, 08:00 PM
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Re: Help! No Heat!!

HEATER CORE if u would have told me a week ago i would have shipped u my new one for free. i had to shaved your heat for my rims to fit (REGRETIN THAT its gettin cold out lol) so thats why im buying a 96 s10 for $600 not 6000 600......

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post #9 of 33 Old 10-28-2007, 10:31 AM
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Re: Help! No Heat!!

Quote:
my trucks ac/heater doesnt work all that well either, only the bottom vents blow. odd?
mine has the same prop do you no how to fix it
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post #10 of 33 Old 10-29-2007, 11:43 PM
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Re: Help! No Heat!!

Sounds like vacuum problems to me. Either bad actuators or bad vacuum lines.

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post #11 of 33 Old 10-30-2007, 12:38 AM
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Re: Help! No Heat!!

First I would check the heater core, next I would check for blockage in the air routes, (hoses from fans) worked on my wifes car a week ago with a simular problem and found so much debri, in the form of pine needles and leafs, etc. Once I pulled it all out, wow, heat.
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post #12 of 33 Old 11-04-2007, 08:50 AM
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Re: Help! No Heat!!

I tried this on my 2001. I havent had heat for 2.5 years, and I was not going to pay the 1000 to change the heater core! It took me 15 minutes, and I now have heat!
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post #13 of 33 Old 11-05-2007, 09:40 PM
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Re: Help! No Heat!!

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Originally Posted by 2500avalanche View Post
I tried this on my 2001. I havent had heat for 2.5 years, and I was not going to pay the 1000 to change the heater core! It took me 15 minutes, and I now have heat!
I'm having a similar problem with my 2002 S10. Temp gauge goes up, turn on the heat and all I get is cool air through both the floor vents and dash vents. Steady blowing air through the dash vents even when I'm directing it through the floor vents only.

Seems like some sort of actuator or vacuum problem. Unfortunately, I don't know where the actuator and vacuum hoses are at. Can anyone direct me towards those items?

Thanks.
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post #14 of 33 Old 11-10-2007, 01:21 PM
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Re: Help! No Heat!!

Quote:
Originally Posted by drewbad View Post
Its getting cold out and my truck isnt making warm air! I changed the thermostat. When I turn the fan to the off position and wait, then turn it on, I get a small blast of warmth, but then turns cold again.

What gives??
I found this heater core back flush procedure on one of the posts somewhere. Has pictures and everything. I just finished back flushing the heater core on my 2002 S-10. The heat works great now!

I was getting very little heat in the vents and I couldn't get air to flow through the vents correctly. When I had the defroster or the heat on, the air would still flow through the a/c vents into the cab. I checked the heater core hoses and, sure enough, one was warm/hot and the other was cold.

I followed the procedures on the attached link and it worked great! The only things I did differently: I attached a 1/2 inch garden hose with the end cut off directly to the small firewall hose and attached some clear vinyl tubing (3/4" inside diameter) to the large outlet (on the left). I also soaked it for about 30 minutes with radiator flush.

http://aycu21.webshots.com/image/308...1713342_rs.jpg

Many, many thanks to whomever took the time and trouble to post this procedure and the pics. Unfortunately I can't find the original post to thank them in a reply.

Good luck.
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post #15 of 33 Old 11-14-2007, 07:31 PM
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Re: Help! No Heat!!

I had this same problem in my wifes 2000 silverado. Come to find out I had an air bubble in it. I got the truck up to running temp and slowly pulled the out line off the heater core. Dont pull it off all the way you'll get antifreeze everywhere. You can hear the air coming out when doing it. After that the truck started blowing hot to where you only need it on low.

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post #16 of 33 Old 11-17-2007, 05:14 PM
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Re: Help! No Heat!!

In a nutshell.
Make sure your cooling system is working (not overheating), and make sure the coolant is topped off.
Make sure your tstat is working (not running too cool). An inop tstat, or even one rated to open cooler can affect the heating system.
Backflush the heater core. Pull both hoses (NOT @ THE BULKHEAD) and use you hose sprayer to push water through both ways. If there's crap in there, this can help.
After that I'd go for a new core.

NOW... about airflow.
Heat selection runs off a cable (to the blend door). Make sure this works. There is an adjustment too.
Vent selection runs off vacuum. Make sure it is hooked up. You can take a mightyvac and pull a vacuum on just that part of the system to test it. You can also pull the cover off, and test each tube seperately.

If there's any more ?'s, just post em up

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post #17 of 33 Old 01-11-2009, 09:30 PM
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Red face Re: Help! No Heat!!

Quote:
Originally Posted by drewbad View Post
Its getting cold out and my truck isnt making warm air! I changed the thermostat. When I turn the fan to the off position and wait, then turn it on, I get a small blast of warmth, but then turns cold again.

What gives??

Just fixed 2001 blazer low heat problem. I bought (2) 5/8 to 3/4 hose adapters and carefully removed and reversed hoses at heater core. I drove the truck 20 minutes and had to turn the heat down it was so hot. Then I removed the adapters and hooked up hoses the way they were. All is good now.

Note: I used a small meat hook to carefully break the hoses loose from the bulkhead I didn't want to cause leaks and have remove the dash to replace heater core.
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post #18 of 33 Old 01-11-2009, 11:43 PM
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Re: Help! No Heat!!

11-17-2007, 03:14 PM

Really? Ever heard of a dead thread. At least you used the search feature but if you done it on a 2001 it wasn't a 60 degree v6 so your in the wrong section to boot.

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post #19 of 33 Old 01-12-2009, 02:44 PM
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Re: Help! No Heat!!

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Originally Posted by neo71665 View Post
11-17-2007, 03:14 PM

Really? Ever heard of a dead thread. At least you used the search feature but if you done it on a 2001 it wasn't a 60 degree v6 so your in the wrong section to boot.
I can't argue with this!

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post #20 of 33 Old 01-12-2009, 04:39 PM
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Re: Help! No Heat!!

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Originally Posted by SH-60B View Post
I can't argue with this!


Thats a first

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post #21 of 33 Old 12-11-2009, 01:16 PM
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Re: Help! No Heat!!

...
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post #22 of 33 Old 12-11-2009, 01:16 PM
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Re: Help! No Heat!!

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Originally Posted by drewbad View Post
Its getting cold out and my truck isnt making warm air! I changed the thermostat. When I turn the fan to the off position and wait, then turn it on, I get a small blast of warmth, but then turns cold again.

What gives??
For anyone with this exact problem.. i.e. it blows hot for a second or two then goes and stays cold, it's NOT the heater core. Key phrase: "blows hot for a bit". It's a broken gear in the blend door actuator that's behind the glove box.
Dealer wants 6 hrs. Start to finish was 20min with the right tools. If you don't have time and want heat, make sure key is off and temp set to heat, while watching and listening to the actuator, turn key back on. The actuator will actuate to the hot side and back to cold because it's confused... repeat steps and when the actuator is at full hot position, unplug it. You can plug it in when the weather gets warm again...
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post #23 of 33 Old 03-26-2010, 05:13 PM Thread Starter
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Re: Help! No Heat!!

I won't let this thread die.
A flush ended up fixing this. I must of had a clog or maybe even air in the system, but now it's a couple years later and another heat problem.
I'm back searching threads because I'm getting glycol in the airvent so I prolly need to tear the dash out and check out the core. Good thing it's getting warm..
Funny that i came across my own thread! Lots of good info in it.
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post #24 of 33 Old 10-05-2010, 12:43 PM
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Re: Help! No Heat!!

almost three years old and still alive. After reading what yall have wrote im going in and checking out my truck.

88 4x4 4.3 with 3 inch lift sitting on 31/10.5's extended cab with A/C (had to aid that)
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post #25 of 33 Old 08-15-2012, 12:58 AM
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Re: Help! No Heat!!

I'll bring it back now because I'm having this problem. I'll be changing my t-stat in the morning hopefully to fix it. It'll be cold soon.
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post #26 of 33 Old 08-15-2012, 10:07 AM
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Re: Help! No Heat!!

Holy batcrap Batman... it won't die!

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post #27 of 33 Old 09-27-2012, 02:48 AM
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Re: Help! No Heat!!

Still not letting it die. New member here, found because I recently purchased my S10 ZR2 (used, of course) and am also having this problem. However, I seem to be in a strange bind. I'm getting hot lines both in and out (as best as I can tell) with absolutely no heat. I can hear the servo move when I turn the heat all the way up, and my thermostat is acting perfectly normal. I don't know enough about the truck to diagnose this myself, and so far the only recommendation I've gotten is to have the heater core replaced, which is either expensive, or a HUGE PITA. While I'm betting I could do it in a weekend, I don't want to if I don't have to. Any suggestions beyond those offered already would be most appreciated.
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post #28 of 33 Old 09-30-2012, 10:09 PM
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Re: Help! No Heat!!

I f you are getting hot hoses both in and out of the core then the core is open and not needing a flush. If not getting cooland in the passenger floor or smellilng coolant from your vents, then the core is fine and not needing changed. I am thinking of the blend door operation. open the heater control panel and check that the cable is attached to the body with a screw-- seen several unhooked and the door does not change.

good luck

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post #29 of 33 Old 12-22-2013, 11:58 AM
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Re: Help! No Heat!!

I am having a similar problem with my 2001 S-10. Sometimes I get a brief blast of heat, then it goes cold.

I just flushed out the heater core, and installed a new thermostat. That didn't help. Additional info: both hoses to heater core remain cold. I'm at a loss as to where to proceed.
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post #30 of 33 Old 12-22-2013, 03:47 PM
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Re: Help! No Heat!!

update: I noticed that if I now raise the engine speed, I will get heat from the vent. But it will get cold again when I return to idle.

I also noted that so far the lower radiator hose is not hot while the upper one is.
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post #31 of 33 Old 11-16-2014, 05:43 PM
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Question Re: Help! No Heat!!

Just went to Auto Zone and bought the two under the hood hoses that run from my heater core and flushed my heater core out with a garden hose,got the water running clear on both openings,connected my hoses back ( the new ones ) bingo,I have heat again,for how long I dont know.... I put a new Thermostat in about a month ago with no luck...I,m looking at my vacuum lines and replaced a couple of those but now see more that I need to replace because inside the radiator the water is not flowing like it should,Im not sure if this whole heating ,cooling system is controlled by vacuum or not ?????? Anyone happen to know....
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post #32 of 33 Old 11-16-2014, 05:57 PM
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Question Re: Help! No Heat!!

Just went to Auto Zone and bought the two under the hood hoses that run from my heater core and flushed my heater core out with a garden hose,got the water running clear on both openings,connected my hoses back ( the new ones ) bingo,I have heat again,for how long I dont know.... I put a new Thermostat in about a month ago with no luck...I,m looking at my vacuum lines and replaced a couple of those but now see more that I need to replace because inside the radiator the water is not flowing like it should,Im not sure if this whole heating ,cooling system is controlled by vacuum or not ?????? Anyone happen to know....
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post #33 of 33 Old 11-17-2014, 03:21 PM
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Re: Help! No Heat!!

Jesus this thread may never die.

I had this happen on my ex-wife's 2000 Blazer. It had that Dexcool crap in it, and it clogged up everything. I backflushed the system with the little cheap Peak kit and what do you know! Heat. Drained the rest of that garbage out of the system. GM should be sued over Dexcool.



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