Heater not working!

Tiny
NATEW51
  • MEMBER
  • 1999 HONDA ACCORD
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 137,000 MILES
Hi Everyone, I've got a 99 Honda Accord and I've been fighting heater issues for a 2 years now. There really doesn't seem to be any rhyme or reason as to why it is not working properly and the shops have not been able to really figure it out either. The core is not leaking and the hoses in and out of the heater core are good and hot, so the water is circulating. Last time I had it worked on was exactly 1 yr ago. The flushed the heater core and actually reverse flushed it, but I'm not 100% sold that that is actually the issue, because nothing ever really flushes out. The heater has been working great up until 2 days ago when my alternator went. I've replaced the alternator and now the only time the heater seems to blow warm is when I idle it up to about 3K. As soon as I back off, the heater cools off. Could this be the core is just bad or could it be something with electronic doors not opening and closing properly due to the issue I had w/ the alternator. The car has climate control, and I just hate to pull the heater core unless absolutely necessary because it is such a huge job and will cost lots of $'s. Any help would be very much appreciated. Thanks in advance!
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Sunday, January 17th, 2010 AT 12:06 PM

12 Replies

Tiny
KHLOW2008
  • EXPERT
Hi natew51,

Try entering the self diagnostic to see if you can come up with anything.

ENTERING SELF-DIAGNOSTICS

1 . Turn ignition on. Turn blower switch OFF. Place recirculation control knob in recirculated air position (indicator light will come on). Press and hold recirculation control switch to fresh air position (indicator light goes off).

2. Continue to hold recirculation control switch until indicator light comes on for 2 seconds. At this point it will blink the Diagnostic Trouble Codes (DTCs) to indicate the faulty component. One blink indicates air mix control motor, 2 blinks indicates mode control motor, and 3 blinks indicates evaporator temperature sensor. If indicator lights come on, test appropriate component.


http://www.2carpros.com/forum/automotive_pictures/192750_HVACDiagnostic99AccordFig06_1.jpg



NOTE:
Fault information is not retained in memory. In case of multiple problems, the light will indicate the DTC with the least number of blinks.

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Wednesday, January 20th, 2010 AT 11:40 AM
Tiny
KEN
  • ADMIN
Hello,

These cars had a problem with trapping air inside the heater core which it sounds like is your problem. With the car nice and hot with the heater running full blast engine running as well jack the rear of the car up as high as you can, this will release the air pocket and make the heater work again.

Here is a guide that can help as well.

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

Please let us know what happens.

Cheers, Ken

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Tuesday, January 30th, 2018 AT 12:14 PM
Tiny
NATEW51
  • MEMBER
You are a genius Ken that was the problem all along. I will remember this site well, you saved me my sanity!
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Tuesday, January 30th, 2018 AT 12:15 PM
Tiny
RAUL8
  • MEMBER
  • 1999 HONDA ACCORD
  • 4 CYL
  • FWD
  • AUTOMATIC
  • 123,000 MILES
Heater problem
1999 Honda Accord 4 cyl Front Wheel Drive Automatic 123000 miles

no heat when cold
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Tuesday, January 30th, 2018 AT 12:15 PM (Merged)
Tiny
KHLOW2008
  • EXPERT
Hi raul8,

A faulty thermostat would result in no heat when cold.
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Tuesday, January 30th, 2018 AT 12:15 PM (Merged)
Tiny
GMAC0603
  • MEMBER
  • 1999 HONDA ACCORD
Heater problem
1999 Honda Accord 4 cyl Two Wheel Drive Automatic 124KM miles

Hi experts, I'm not getting any heat even though fan works fine, the knob isn't stripped, I can hear a change of wind sound when I go from cold to hot on the dial. Not even warm heat is coming out.

Thanks in advance
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Tuesday, January 30th, 2018 AT 12:15 PM (Merged)
Tiny
F4I_GUY
  • EXPERT
Your heater core is most likely clogged. Try to flush it out, or replace it.
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Tuesday, January 30th, 2018 AT 12:15 PM (Merged)
Tiny
ED3013
  • MEMBER
  • 1999 HONDA ACCORD
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 170,000 MILES
Heater problem
1999 Honda Accord 6 cyl Front Wheel Drive Automatic 170000 miles

99 Honda accord, V6 w/ 170K automatic. I'm only getting luke warm heat. I have changed the thermostat (OEM), the water pump, filter behind the dash board, and flushed the radiator and heating core. All work was done separately and the heat worked for a day or so then no heat. Could it be the heating core or the hose? If so how much would be a average price for such repairs?
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Tuesday, January 30th, 2018 AT 12:15 PM (Merged)
Tiny
BRUCE HUNT
  • EXPERT
It is possible that you have a leak in the radiator not allowing the vehicle to properly pressurize. I might have the system pressure tested.
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Tuesday, January 30th, 2018 AT 12:15 PM (Merged)
Tiny
ED3013
  • MEMBER
How would a radiator leakage affect the heat? If that is the problem what would remedy it?
I don't see any coolant loss or any leakage when the car is parked.
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Tuesday, January 30th, 2018 AT 12:15 PM (Merged)
Tiny
ANIRBAN TARAFDER
  • MEMBER
  • 1999 HONDA ACCORD
  • 4 CYL
  • FWD
  • AUTOMATIC
  • 96,000 MILES
Heater problem
1999 Honda Accord 4 cyl Front Wheel Drive Automatic 96000 miles

Hi,

I have this strange problem. Heater is not working at postion 1. At position 2 it blows hot air only if speed is above 40 mph. When I stall the engine cool/normal air flows. At position 3 and 4 again the temp falls for the hot air.

I got my thremostat changed but still problem persists.
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Tuesday, January 30th, 2018 AT 12:16 PM (Merged)
Tiny
KHLOW2008
  • EXPERT
Hi Anirban Tarafder,

Seems there is insufficient coolant flow to provide the heat and you need to check,
1. Clogged heater hose.
2. Heater valve not opening sufficiently due to operating cable out of adjustment.

The blower speed resistor is bad so you don't have 1st speed.
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Tuesday, January 30th, 2018 AT 12:16 PM (Merged)

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