Heater not working?

Tiny
TOMOTTERMAN
  • MEMBER
  • 2004 CHEVROLET S-10
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 100,411 MILES
The heat guage now reads 200 degrees following replacement of thermostat, up from 160. Still only getting cold air, what's up?
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Wednesday, January 14th, 2009 AT 3:52 PM

44 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,005 POSTS
Hi:
With the engine at operating temp and the heater on, feel both heater core hoses. Both should be hot. This guide should help us fix it

https://www.2carpros.com/articles/car-heater-not-working

and this video

https://youtu.be/SNRb6pSwYuU

Let me know what you find.

Joe
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Thursday, January 15th, 2009 AT 7:49 PM
Tiny
TOMOTTERMAN
  • MEMBER
  • 2 POSTS
I felt the lines to the heater core, the feed line was hot the return line was cold. I disconnected the lines and blew in through the return line with an air compressor. I now have heat.
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Friday, January 16th, 2009 AT 7:52 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,005 POSTS
Glad to hear that it worked. It must have been plugged. You may want to flush it when the weather gets a little better.

Joe
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Friday, January 16th, 2009 AT 8:16 AM
Tiny
RICHSTRUCK
  • MEMBER
  • 4 POSTS
  • 2003 CHEVROLET S-10
  • 4.3L
  • V6
  • 4WD
  • AUTOMATIC
  • 121,000 MILES
Have replaced thermostat, flushed heater core, still get heat sometimes, but does not last. Tested the temp control switch has 9.92 ohms, and it is variable with turn of the control shaft. What does this temperature control switch actually control? Is it a valve? The truck runs great. Runs about 210 degrees and is full with antifreeze. Does not overheat. It used to have heat really fast, the heater core has been replaced, and worked fine for a winter, it was working then it started to have sometimes heat.
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Saturday, October 3rd, 2020 AT 12:09 PM (Merged)
Tiny
SATURNTECH9
  • MECHANIC
  • 30,870 POSTS
There is a temperature blend door actuator to control the temp. Here is a guide to show you what you are in fro when changing it out with the location of the actuator for you car below.

https://www.2carpros.com/articles/replace-blend-door-motor

this guide can help as well

https://www.2carpros.com/articles/car-heater-not-working

With the engine up to operating temp are both the heater hoses going into the heater core getting too hot to hold?

Check out the diagrams (Below). Please let us know what you find.

Cheers,
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Saturday, October 3rd, 2020 AT 12:09 PM (Merged)
Tiny
RICHSTRUCK
  • MEMBER
  • 4 POSTS
With the truck up to operating temperature, the supply hose (the larger of the two) is hotter than the smaller one?
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Saturday, October 3rd, 2020 AT 12:09 PM (Merged)
Tiny
SATURNTECH9
  • MECHANIC
  • 30,870 POSTS
Is sounds like the heater core working correctly, did you get a chance to check the actuator?
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Saturday, October 3rd, 2020 AT 12:09 PM (Merged)
Tiny
RICHSTRUCK
  • MEMBER
  • 4 POSTS
No, I can hold on to both of them. Is there something that I can pour into the heater core to flush the dexcool that usually plugs the core?
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Saturday, October 3rd, 2020 AT 12:09 PM (Merged)
Tiny
SATURNTECH9
  • MECHANIC
  • 30,870 POSTS
Your not getting coolant circulation if both your upper and lower radiator hoses arent getting too hot to hold?I would address that maybe you got a bad thermostat?Did you put the thermostat in correctly?
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Saturday, October 3rd, 2020 AT 12:09 PM (Merged)
Tiny
RICHSTRUCK
  • MEMBER
  • 4 POSTS
I changed out the actuator and now I have heat again! Thank you so much I has freezing. I love this site
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Saturday, October 3rd, 2020 AT 12:09 PM (Merged)
Tiny
SATURNTECH9
  • MECHANIC
  • 30,870 POSTS
You welcome.
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Saturday, October 3rd, 2020 AT 12:09 PM (Merged)
Tiny
COLIN JENKINS
  • MEMBER
  • 1 POST
  • 2003 CHEVROLET S-10
  • 4.3L
  • V6
  • 4WD
  • AUTOMATIC
  • 96,000 MILES
If I pull return line off heater core run the motor coolant will circulate. When hook it back up have heat for couple minutes then lose it again. Seems like it loses its prime, could this be a water pump problem? I have flushed heater core and truck runs normal temperature around 190.
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Saturday, October 3rd, 2020 AT 12:09 PM (Merged)
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good morning,

When the hoses are hooked up, do both feel hot?

It sounds like the core is clogged. Did you flush it both ways with a garden hose? If you did then most likely it is a bad heater core.

If you had a bad water pump, it would run hot and possibly overheat.

Roy

https://www.2carpros.com/articles/car-heater-not-working

https://www.2carpros.com/articles/replace-heater-core
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Saturday, October 3rd, 2020 AT 12:09 PM (Merged)
Tiny
TONYTHETIGER
  • MEMBER
  • 1 POST
  • 2003 CHEVROLET S-10
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 120,000 MILES
When I am in park the heater blows cold air and I can smell anti-freeze. When I am driving the heater works perfect and there is no smell. Any info would be great.
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Saturday, October 3rd, 2020 AT 12:09 PM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Try replacing the thermostat and see what happens. The heater is getting cold at park bcuz the water pump is not turning that fast along with the thermostat sticking open compared to higher speed.
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Saturday, October 3rd, 2020 AT 12:09 PM (Merged)
Tiny
KINGRCR
  • MEMBER
  • 1 POST
  • 2003 CHEVROLET S-10
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 48,000 MILES
I have a 2003 chevy s-10 with a 4.3 liter motor. My question is when I turn on the heat it blows cold air. The thermostat is working fine running about 190 degrees what do you think is causing this and what or how should I check it.
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Saturday, October 3rd, 2020 AT 12:10 PM (Merged)
Tiny
LEGITIMATE007
  • MECHANIC
  • 5,121 POSTS
I think the thermostat is stuck closed and is not allowing the hot coolant to the heater core.
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Saturday, October 3rd, 2020 AT 12:10 PM (Merged)
Tiny
WICKED360
  • MEMBER
  • 1 POST
  • 2003 CHEVROLET S-10
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 60,000 MILES
My 03' Auto S-10 is at 60,000 Miles. I recently discovered (during the cold winter months) That the heat does not work. It only blows cold air. The fuses are fine, the heater core has no leakage or smoking (I have had 2 blown cores in the past and do not believe it is the problem), the AC unit works just fine. I am at a loss to what the problem may be. Any suggestions?
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Saturday, October 3rd, 2020 AT 12:10 PM (Merged)
Tiny
PEAR69
  • MECHANIC
  • 1,482 POSTS
Your thermostat is probably stuck open. A thermostat works as follows. When you start your engine the coolant is cool. At this point the thermostat is closed, not allowing coolant to run through the radiator--where it is cooled. However your water pump is always pumping coolant somewhere, and regardless of whether the t. Stat open or closed, the coolant is usually flowing through the heater core and the engine. As the engine creates more heat the coolant heats up also. When the coolant reaches 185 degrees or so, the thermostat opens and allows coolant to flow through the radiator. As air passes through the fins of the radiator, the coolant is cooled down to safer levels for the engine. If the thermostat sticks open or fails open, the coolant will constantly flow through the radiator and be constantly cooled. This will not allow the coolant to heat up thus you are left in the cold. Your engine will be happy, but unless you like to be cold, you will not be happy.

BTW-- a thermostat can stick or fail closed which will cause over heating and eventualy engine failure, so have your thermostat checked and/or replaced. Let me know how you make out.
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Saturday, October 3rd, 2020 AT 12:10 PM (Merged)
Tiny
BRYAN2
  • MEMBER
  • 1 POST
  • 2003 CHEVROLET S-10
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 75,000 MILES
My heat doesn't work until my engine overheats and the heat kicks on and cools my engine back to normal temperature.?
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Saturday, October 3rd, 2020 AT 12:10 PM (Merged)

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