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Heater no blowing hot?

Tiny
MIPRICE
  • MEMBER
  • 1998 CHEVROLET BLAZER
  • 4 CYL
  • 4WD
  • AUTOMATIC
  • 155,000 MILES
My AC is blowing super cold. When I turn to a heat setting, barely warm air blows in the floorboard. Should it be warmer? I am no mechanic, but I think so.
Tuesday, November 10th, 2009 AT 8:11 AM

72 Replies

Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
Welcome to the forum, feel of the heater hoses, see if they get hot. you may also have to check coolant flow through the heater core. It is also possible, the blend doors under the dash aren't working correctly. A faulty thermostat could be another issue?

This guide can help us

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

Please run down this guide and report back.
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Tuesday, November 10th, 2009 AT 3:51 PM
Tiny
PPNJ4
  • MEMBER
  • 3 POSTS
It was the heater core plugged up on my car BTW
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Friday, January 3rd, 2020 AT 3:13 PM
Tiny
JTRISS02
  • MEMBER
  • 1 POST
  • 1998 CHEVROLET BLAZER
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 103,000 MILES
I have a 1998 chevy blazer with a 4.3 v-6. One day I get in and the heater just stopped blowing warm air. The guage still get's up to operating temps but still blows cold air. The blower still blows hard and I replaced the radiator cap and it is always full of coolant.
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Friday, January 3rd, 2020 AT 3:13 PM (Merged)
Tiny
CARLUCCIJA
  • MEMBER
  • 29 POSTS
Your blazer might have a bad heating coil. My Uncle had a Blazer of the same year and his did the same thing and it turned out to be the heater coil
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Friday, January 3rd, 2020 AT 3:13 PM (Merged)
Tiny
DBAST1
  • MEMBER
  • 1 POST
  • 1998 CHEVROLET BLAZER
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 82,500 MILES
I have heat some times and others not at all. We have changed the thermostat and flushed the system twice. The radiator does not get very hot even though the gauge says 190, also the hose's do not get very hot. HELP
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Friday, January 3rd, 2020 AT 3:13 PM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Test the water pump:

One way to test for a bad water pump is to squeeze the upper radiator hose when the engine is hot and idling. Careful, because the hose will be HOT! If you do not feel much coolant circulating through the hose when you rev the engine, the pump may be bad. The other cause might be a bad thermostat that is not opening properly (remove and inspect the thermostat), or a clogged radiator.
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Friday, January 3rd, 2020 AT 3:13 PM (Merged)
Tiny
BROOKE7878
  • MEMBER
  • 3 POSTS
  • 1998 CHEVROLET BLAZER
  • 200,000 MILES
I have a 1998 chevy blazer 2wd 4.3 engine. Have no heat. We have changed the heater core, thermostat, blend door actuator and still no luck. Both heater core hoses are hot. Can feel the heat inside when glove box is out but not coming thru any vents as hot air. The air is luke warm. Please help. Brooke
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Friday, January 3rd, 2020 AT 3:13 PM (Merged)
Tiny
FIXITMR
  • MECHANIC
  • 9,990 POSTS
Probably blend door problem.
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Friday, January 3rd, 2020 AT 3:13 PM (Merged)
Tiny
FIXITMR
  • MECHANIC
  • 9,990 POSTS
Your gonna have to remove actuator and manually move door to see it that helps.
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Friday, January 3rd, 2020 AT 3:13 PM (Merged)
Tiny
FIXITMR
  • MECHANIC
  • 9,990 POSTS
Did you get right actuator? There are 2, 1 manual and 1 auto climate controls.
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Friday, January 3rd, 2020 AT 3:13 PM (Merged)
Tiny
MAGOSTINI
  • MEMBER
  • 2 POSTS
  • 1998 CHEVROLET BLAZER
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 70,000 MILES
My 98 blazer has little or no heat, one of my heater core lines stays cold, if I raise the idle, heat seems to get hotter. Do I have a bad water pump.
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Friday, January 3rd, 2020 AT 3:13 PM (Merged)
Tiny
LEGITIMATE007
  • MECHANIC
  • 5,121 POSTS
Not necessarily, your themostat could be stuck. I would change the thermostat
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Friday, January 3rd, 2020 AT 3:13 PM (Merged)
Tiny
BROOKE7878
  • MEMBER
  • 3 POSTS
I am unsure which one it is. Not sure on how to manually move the door. Where exactly is the door at?
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Friday, January 3rd, 2020 AT 3:13 PM (Merged)
Tiny
MAGOSTINI
  • MEMBER
  • 2 POSTS
Certainly sounds less difficult, I will give that a shot first. Thanks
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Friday, January 3rd, 2020 AT 3:13 PM (Merged)
Tiny
BROOKE7878
  • MEMBER
  • 3 POSTS
I have a photo of the box it came in but it will not let me upload it with my message.
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Friday, January 3rd, 2020 AT 3:13 PM (Merged)
Tiny
LEGITIMATE007
  • MECHANIC
  • 5,121 POSTS
Yes most defininately
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Friday, January 3rd, 2020 AT 3:13 PM (Merged)
Tiny
FIXITMR
  • MECHANIC
  • 9,990 POSTS
Maybe reduce file size or change format?
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Friday, January 3rd, 2020 AT 3:13 PM (Merged)
Tiny
GERALDINE BUGEJA
  • MEMBER
  • 2 POSTS
  • 1998 CHEVROLET BLAZER
Hi,
I have a 98 Chevy Blazer, 114,000 miles with a V6 engine. I have no heat. Just installed a new A/C Heater Control Assembly, still not working. Took it back to the mechanic and my radiator was clogged because a previous mechanic had put in a stop leak.
Bought a new radiator. Still no heat. Mechanic suggessted that the water pump might also be clogged because of the Stop Leak that was added.
Can I trust this mechanic? What's next?
Thanks
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Friday, January 3rd, 2020 AT 3:13 PM (Merged)
Tiny
MERLIN2021
  • MECHANIC
  • 17,250 POSTS
If a stop leak was used, run the car to normal temp, then feel the two hoses going into the heater core on the firewall, be carful they should be hot!
If one or both are only warm, the core is plugged with the stop leak too. If they are hot try changing the thermostat!
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Friday, January 3rd, 2020 AT 3:13 PM (Merged)
Tiny
GERALDINE BUGEJA
  • MEMBER
  • 2 POSTS
Hey Merlin2021 you suggessted a new thermostat, I forgot to mention that the mechanic installed a new one already! Any other suggestions would be appreciated.

Thank you,
Gerry
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Friday, January 3rd, 2020 AT 3:13 PM (Merged)

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