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Heater not working?

Tiny
RDCN214
  • MEMBER
  • 2003 HONDA ACCORD
Engine Cooling problem 6 cyl Front Wheel Drive Automatic 105000 miles

Hi, I have a Honda Accord 2003 v6 and have no heat coming from the vents. The passenger side gets warm and the drivers side blow cold.

Things I have already replaced
1. Thermostat
2. Water Pump, timing belt, oil seals since I was in there
3. New Heater Core. What a job this was.
4. Upper and lower hoses
5. Heat control Valve
6. Radiator cap, and other smaller hoses that circulate antifreeze
7. Reservoir hoses

I have also flushed the system 3 times. Checked all the vent doors are opening and closing correctly. Also ordered the ATF Warmer that circulates antifreeze and warms the ATF fulid. This is on the top of transmission.

When the RPM's are rev'ed up a bit you can hear the coolant flowing in the heater core. From my research and asking questions, I was told this is AIR in the system. I was told by Honda, that when they bleed the 03 accord they lift the front of car, so the air can escape the highest point. Tried this with the car on a slope and also up on ramps, with a hose and funnel attached to the radiator ensuring the coolant is higher than the heater core. Let it run til the thermostat open about 5 times and still no heat. I feel like I tried everything on this car and have pretty much given up hope of getting heat out of the car.

I need help in getting the air out the system. There is no bleed screw on this car.

The heater hoses do heat up, but one more than the other. The hose that goes to the lower part of the heater core (the one that also has the valve) heats up more than the upper hose. The upper hose usually heats up to comparable heat when I have the engine rev'ed up to about 2500 rmp's.

Which direction would the coolant flow? Does it flow into the heater core from the bottom or the top? Bottom, being the hose with the valve on it?

One thing I forgot to mention in my initial post is that when the car is cold, like in the morning the upper and lower radiator hoses are sucked in?

Bought another radiator cap as the other one seemed like the rubber gasket was worn. I hope the new cap will resolve that, but was wondering if that would be caused by air in the system or a faulty radiator cap?
When I rev the engine I still hear the coolant flowing sound in the heater core?

After the storm in the northeast passes I will disconnect the hoses from the core and attach a garden hose to flush out both passages of the core in hopes to clear out any clogs in there.

What is the proper procedure for getting air out of the system when the car has no bleeder screw? What else can be the cause of this problem?

Service Writer, please steer me in the right direction.

Happy Holidays!
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Thursday, December 17th, 2009 AT 11:08 PM

20 Replies

Tiny
SERVICE WRITER
  • MECHANIC
  • 9,123 POSTS
I found a Technical service bulletin and guides that can help us fix it.

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

Turn the selector to a/c is there cold or warm air that comes out? If it is warm air, then :

SOURCE: Honda Service News

TITLE: Heater Blows Cold Air, A/C Blows Warm Air

APPLIES TO: all A/C-equipped Honda models that use a heater valve cable.

SERVICE TIP:

Got a vehicle in your shop that blows cold air from the heater or warm air from the A/C ? The problem could just be the heater valve cable has slipped off the heater valve arm. There's a real easy fix for this problem. Slip the heater valve cable back onto the heater valve arm. Then cut yourself a 10 mm length of 3.5 mm vacuum hose and slide it onto the arm. This holds the cable on the arm nice and snug so it won't slip off.

Out of curiosity, are the heater hoses both hot at the firewall? Which direction would the coolant flow? It flows into the heater core from the bottom, being the hose with the valve on it.

One thing I forgot to mention in my initial post is that when the car is cold, like in the morning the upper and lower radiator hoses are sucked in?

Another radiator cap was a good idea, curious how that works out.

Check for a collasping hose from the radiator to the overflow bottle. If it isn't allowing coolant to get into the system as it cools, the air pocket may remain.
IF the system can not eliminate the pocket by drawing in coolant from the reservior the pocket can remain. I would do this first.

I agree, when you rev the engine and still hear the coolant flowing sound in the heater core, that sounds like the air pocket.

I doubt the core is clogged. You can pull the top heater hose off and start the car to see what kind of flow is there to verify.

The proper procedure for getting air out of the system on this is to leave the cap loose, (do raise the front), start the engine, allowing the cooling fan to cycle twice and close the cap.

I think you are close to nailing this. Post back as needed.
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Friday, December 18th, 2009 AT 5:19 AM
Tiny
RDCN214
  • MEMBER
  • 3 POSTS
Service Writer, thanks for the prompt reply. The TSB is a good one, but not the symptoms of the car.

I checked the blend door actuator and then changed it now the heater works great! Thanks for your help on this one :)
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Friday, December 18th, 2009 AT 9:18 PM
Tiny
SERVICE WRITER
  • MECHANIC
  • 9,123 POSTS
Use 2CarPros anytime, we are here to help. Please tell a friend.

Cheers, Ken
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Saturday, December 19th, 2009 AT 6:07 AM
Tiny
PROCTORDM
  • MEMBER
  • 1 POST
  • 2003 HONDA ACCORD
  • 4 CYL
  • AUTOMATIC
  • 272,000 MILES
What could cause the heat to stop working?
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Tuesday, December 1st, 2020 AT 11:03 AM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
If the blower motor is functioning and blowing but no heat-check the thermostat, heater core and the air blend door/actuator
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Tuesday, December 1st, 2020 AT 11:03 AM (Merged)
Tiny
ELIZABETH HAYES
  • MEMBER
  • 1 POST
  • 2002 HONDA ACCORD
  • 3.0L
  • V6
  • 2WD
  • AUTOMATIC
  • 200 MILES
My AC/heat even defrost do not work at all. Nothing comes out the vents when on and when I turn it on the fan sounds like it is hitting something. So I took it out and cleaned it then put it back and it still makes the same noise. I do not have a lot of money so cheaper the better. Thank you the sooner the better as well.
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Tuesday, December 1st, 2020 AT 11:03 AM (Merged)
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
Hi and thanks for using 2CarPros. Com.

Are you sure the fan motor is not bad? I would remove it and supply power directly to it to confirm it works properly. If it does, then it is hitting something in the box.

Here are the directions specific to your vehicle for removal and replacement. Check through them to confirm something was not put together wrong. The attached pictures correlate with these directions

______________________________

Blower Unit Removal and Installation

SRS components are located in this area. Review the SRS components locations, precautions, and procedures in the SRS section before performing repairs or service.

1. Make sure you have the anti-theft code for the radio, then write down the frequencies for the radio's preset buttons.
2. Disconnect the negative cable from the battery.
3. Remove the dashboard.
4. With air conditioning; remove the evaporator.
5. Without air conditioning; remove the self-tapping screws, the mounting nut, the mounting bolts and the heater duct.
6. Disconnect the connectors (A) from the blower motor, the blower resistor and the recirculation control motor, then remove the wire harness clip (B). Remove the mounting nuts, the mounting bolt and the blower unit (C).
7. Install the unit in the reverse order of removal, and note these items:
- Make sure that there is no air leakage.
- Enter the anti-theft code for radio, then enter the customer's radio station presets.

_______________________________________

Let me know if this helps or if you have other questions. Note: When you test it outside of the vehicle, make sure the fan itself is tight and the bearing in the motor is not allowing things to wobble.

Take care,
Joe
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Tuesday, December 1st, 2020 AT 11:03 AM (Merged)
Tiny
REBE7177
  • MEMBER
  • 1 POST
  • 2002 HONDA ACCORD
About 5 months ago my car's temperature guage started rising as if my car was overheating, but it actually was not overheating (no smoke & would fall as fast as it would rise). At the same time it was rising, my heat began blowing cold air. I brought it to my mechanic and they changed the thermostat, which seemed to fix the problem for a week or so. The guage would rise and fall intermittently and sometimes not at all (staying normal) when I was driving it. I brought it back to the mechanic and they ran all these tests, but were unable to find the problem (they hooked it up to the computer and all readings were normal). They suggested that I take it to the dealership, b/c they may be better able to pinpoint the problem. The dealership checked everything again (no leaks or anything) and they only idea they had is that I guess they have been getting reports of Civics having a faulty fan switch that can cause the temp. Gauge to intermittently rise. The switch was replaced and all was well for the past 4 months, until a few days ago, it started happened again. I had mentioned this problem to a co-worker and she said she had a similar problem with her Accord and it ended up being a head gasket problem (she didn't have the cold air blowing though). Do you think this may be my problem as well? Wouldn't they check the head gasket as a possible cause based on these symptoms? I don't want to keep driving it if If so, what is a ballpark figure to have this problem repaired? Also, what are the signs your head gasket is going/gone? I don't want to keep driving it if this is the problem without getting it fixed and creating a more expensive repair. I have a 2002 Automatic Honda Civic EX (I believe the engine size is 1.7?) With 133,000 miles on it. Thanks in advance for your help!
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Tuesday, December 1st, 2020 AT 11:03 AM (Merged)
Tiny
BRUCE HUNT
  • MECHANIC
  • 3,754 POSTS
Obvious signs are loss of coolant, overheating, and a white smoke from the exhaust with hard starting and rough engine idle. These are extreme symptoms and yes that could be a symptom. I would watch the level of the coolant very closely. When the vehicle is cold open the radiator cap and see how much fluid it takes and keep an eye on the overflow bottle. Note how much is in there and how much has disappeared. Try to keep it filled to the max line. Let us know after a week of driving what is occurring.
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Tuesday, December 1st, 2020 AT 11:03 AM (Merged)
Tiny
ROBERT82
  • MEMBER
  • 1 POST
  • 2002 HONDA ACCORD
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 99,500 MILES
Will not blow hot air. Is only luke-warm at best. Changed the thermostat but still no hot air. Whats next?
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Tuesday, December 1st, 2020 AT 11:04 AM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Check for a clogged heater hose and heater core-could. Also be a heater control valve, air mix/blend door, or a problem with an actuator or vacuum source.

Check this out:

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

Please let us know what happens.

Cheers
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Tuesday, December 1st, 2020 AT 11:04 AM (Merged)
Tiny
JASSIMKHATTAK
  • MEMBER
  • 1 POST
  • 2002 HONDA ACCORD
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 150 MILES
Hi,

My car heater has not been working well. Most of the time its not even heating. My mechanic has changed the thermostat, flushed the collant system and checked the blower which is working. He then said he will change the heater core which could be the problem. He hasnt done that yet but now says that the engine could be running bad.
Do you think you know what the problem could be. Also I am thinking to take it to another mechanic for a second opinion.

Thanks for your help!

Moe.
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Tuesday, December 1st, 2020 AT 11:04 AM (Merged)
Tiny
DAVE'S BIG BACKYARD!
  • MECHANIC
  • 262 POSTS
Sounds like maybe you have a blown head gasket, it puts air pockets in the cooling system. And yes, I would get someone else to look at it. It never hurts to get another set of eyes on the problem.
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Tuesday, December 1st, 2020 AT 11:04 AM (Merged)
Tiny
JOYED92
  • MEMBER
  • 28 POSTS
  • 2000 HONDA ACCORD
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 76,000 MILES
Hi, My car don't blowout hot air form the heating system.
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Tuesday, December 1st, 2020 AT 11:04 AM (Merged)
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
Is the engine running at a normal operating temp? Is the coolant level full? If you start the engne, let it warm up with the heater on high, do both heater core hoses get hot?

Let me know and thanks for using 2carpros. Com

Joe
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Tuesday, December 1st, 2020 AT 11:04 AM (Merged)
Tiny
SSONO
  • MEMBER
  • 1 POST
  • HONDA ACCORD
I have a 2003 Honda Accord. My heater all of a sudden has stopped working. Can someone tell me what might be the problem?
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Tuesday, December 1st, 2020 AT 11:17 AM (Merged)
Tiny
DTMFZR
  • MEMBER
  • 9 POSTS
Is there enough coolant in your car? What do you mean your heater is broken? It blows cold air? No air blows at all? What exactly is the problem?
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Tuesday, December 1st, 2020 AT 11:17 AM (Merged)
Tiny
CMC32H2O
  • MEMBER
  • 1 POST
  • 2002 HONDA ACCORD
Can't get warm air from heater. Flushed system, replaced thermostat, checked heater control valve. Water flowed freely through heater core when flushed and return hose from core is hot. What else could it be?
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Wednesday, December 30th, 2020 AT 11:14 AM (Merged)
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
There is a blend air door that determines if you get A/C or heat from the system. Chances are it isn't working. It is located near the heater core. This guide can help:

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

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Wednesday, December 30th, 2020 AT 11:14 AM (Merged)
Tiny
DANNY L
  • MECHANIC
  • 5,648 POSTS
Hello, I'm Danny.

Here is a tutorial showing how the replace a mode-blend door actuator. It's a small electric motor that opens and closes a door to circulate air flow through certain air ducts in the HVAC box. I've attached picture steps below on how to replace the mode actuator on your car. Hope this helps and thanks for using 2CarPros.
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Wednesday, December 30th, 2020 AT 11:14 AM (Merged)

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