Heater not working

Tiny
FRANXUA1
  • 2004 HONDA ODYSSEY
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 100,000 MILES

My 2004 honda odyssey heater wont heat, neither the front or the back! I changed the thermostat, I purged the system, I changed the cabin air filter and still no heat, the door that changes the settings from hot to cold works fine too, the hose from the heater core does get hot, so Im assuming the heater core its working, the only thing I did noticed its that the fans start working too soon. Any ideas on what it could be?

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Friday, December 31st, 2010 AT 7:07 PM

18 Replies

Tiny
KHLOW2008
  • EXPERT
  • 42,073 POSTS

It sounds like you can be low on coolant even though the hoses are hot it could just be steam and not hot coolant.

Does the system have a coolant leak can you check the level?

Here are a couple of guides and a video to help you check it out.

https://youtu.be/GSE9skKnOgY

and

https://www.2carpros.com/articles/car-is-leaking-coolant

and

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

Please run some tests and get back to us so we can keep helping you.

Cheers

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Saturday, January 1st, 2011 AT 2:02 PM
Tiny
KHLOW2008
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Here is more information I found that will help

HOW TO RETRIEVE A DIAGNOSTIC TROUBLE CODES
The climate control unit has a self-diagnosis function. To run the self-diagnosis function, do the following:

1 Turn the Ignition switch ON (II).

2. Press the AUTO button and then press the OFF button. Continue to hold both buttons down for 1 minute.

If there is any abnormality in the system the temperature Indicator will light up the segment (A through N) corresponding to the error. The temperature indicator will then alternate every second between displaying "88" (all segments lit) and the error code segment (A through N).

NOTE:
The system will only display the DTC when the AUTO and OFF buttons are pressed if you release the buttons the display will go blank. To return the display, simply press the AUTO then the OFF buttons again.

To determine the meaning of the DTC, refer to the DTC Troubleshooting Index. If there is no abnormality the segment will not light up.

Cancelling the Self-diagnosis Function

3. Turn the ignition switch OFF to cancel the self-diagnosis function. After completing repair work run the self-diagnosis function again to make sure that there are no other malfunctions.

(Check the diagrams below)

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Sunday, January 2nd, 2011 AT 2:49 AM
Tiny
FRANXUA1
  • MEMBER

Do you think it could be the water pump?

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Sunday, January 2nd, 2011 AT 6:56 PM
Tiny
KHLOW2008
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  • 42,073 POSTS

If the water pump or cooling system has a leak you would most likely have no heat.

Did you back flush the heater core when replacing the thermostat?

You mentioned purging the the system, did you recheck coolant level when engine cooled down?

When bleeding the system were the heater turned to maximum heat?

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Monday, January 3rd, 2011 AT 2:08 PM
Tiny
FRANXUA1
  • MEMBER

Yea I backed flushed the heater core, and yea I checked the coolant, it was fine, about the heat yea when I did the bleeding the heater was turned at maximum!

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Monday, January 3rd, 2011 AT 6:24 PM
Tiny
KHLOW2008
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You mentioned the fans starting too soon, its a sign the coolant level is low.

Also check the air mix motor and its linkages for proper operations. Switch between A/C and heater and note if the air mix motor are moving and note if the linkages are moving or binding. Remove the air mix motor to check if necessary.

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Monday, January 3rd, 2011 AT 8:43 PM
Tiny
FRANXUA1
  • MEMBER

The fans at the front of the car, but I just realized that when they were starting too son it was because the car didn't have enough anti freeze! Now they are working fine!

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Tuesday, January 4th, 2011 AT 7:29 AM
Tiny
KHLOW2008
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  • 42,073 POSTS

With heater connections to rear of vehicle, there could be a lot of air trapped in system and requires quite some bleeding process.

Redo the bleeding of the cooling system again. Turn heater to max heat and run engine for 5 minutes with radiator cap off. Top up coolant level if it goes down.

Stop engine after 5 minutes. Close radiator cap and run engine till operating temperature. Stop engine and allow to cool. Remove radiator cap to check coolant level. If low repeat bleeding process. Ensure recovery tank has sufficient coolant.

If heater both hoses are hot after 5 minutes of engine running, check the air mix motor and linkages.

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Tuesday, January 4th, 2011 AT 2:59 PM
Tiny
FRANXUA1
  • MEMBER

I have a question, do you think it can be the climate control system, because I just noticed yesterday that the screen that it supposed to tell you the temperature and the position on which you want the air flow doesn't light, I mean it does show the temperature and the position, but it doesn't light, I'm thinking it could be that. Do you think that could be an option!

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Tuesday, January 4th, 2011 AT 5:31 PM
Tiny
KHLOW2008
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Yes, the control panle controls the air flow and if it is faulty, the air mix motor would not movde the blend doors to the correct position.

Remove the air mix motor and manually move the blend door linkages to the heater position to test if the heater works.

When you said no heat, it it blowing cold air as if the A/c Is being operated instead of the heater or there is insufficient heat?

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Tuesday, January 4th, 2011 AT 5:39 PM
Tiny
FRANXUA1
  • MEMBER

The water pump is leaking Im going to have to replace it! Do you happen to know of any link where I can find the timing belt diagram?

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Tuesday, January 18th, 2011 AT 2:21 AM
Tiny
KHLOW2008
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  • 42,073 POSTS

Here is a guide for what you are in for when doing the job less the timing belt.

https://www.2carpros.com/articles/water-pump-replacement

TIMING BELT
Removal

1. Disconnect negative battery cable. Turn crankshaft pulley so that No. 1 piston is at TDC on compression stroke. White mark on crankshaft pulley should align with pointer on front cover. Remove right front wheel. Remove lower engine splash shield. Move auto-tensioner to relieve tension, then remove the generator and power steering pump drive belt(s).

2. Support engine with a jack and wood block under the oil pan. Remove ground cable (if necessary), then remove engine side mount bracket. If necessary, remove dipstick tube from front of engine (discard "O" ring). Remove crankshaft pulley. See Fig. 1. ( A high toruqe impact wrench works but at times it might be rather stiff.

3.Remove upper and lower timing belt covers. See Fig. 2. If reusing timing belt, mark direction of belt rotation for installation reference.

4. Remove one of the battery clamp bolts from battery tray. Grind threaded end of bolt to a partial point (about 45-degree chamfer). Thread battery bolt as shown to hold timing belt adjuster in installed position (hand tighten ONLY). See Fig. 3.

5. If applicable, remove timing belt guide plate from front of crankshaft sprocket. Remove engine mount bracket from front of engine.

6. Remove idler pulley bolt and idler pulley, then remove timing belt.

Installation (New Belt)

1. Ensure that engine is at TDC. Align dimple on timing belt drive pulley with pointer on oil pump. See Fig. 4. Align camshaft pulleys with pointers on back covers.

2. Remove battery clamp bolt from back cover. Remove the timing belt auto-tensioner.

NOTE:
When compressing sealed auto-tensioners, compression pressure should not exceed 2200 lbs. (9800 N).

3. Place sealed auto-tensioner in press. SLOWLY compress tensioner until pin can be inserted through tensioner body, and insert pin. See
Fig. 6. Install auto-tensioner onto engine.

4. Install battery clamp bolt into back cover. Apply liquid thread lock to idler pulley bolt and loosely install idler pulley.

5. Install timing belt in counterclockwise direction in the following sequence:
Crankshaft pulley, idler pulley, front camshaft pulley, water pump pulley, rear camshaft pulley and tension adjust pulley. See Fig. 7. Ensure crankshaft and camshaft pulleys remained aligned with marks on back cover. Tighten idler pulley bolt to specification.

6. Remove stopper or pin from auto-tensioner. Remove battery clamp bolt from back cover, if necessary. Install engine mount bracket to the front of engine. If applicable, install timing belt guide plate with concave surface facing out. Install lower cover, then upper front and rear covers. Clean, then install crankshaft pulley. Lubricate crankshaft pulley bolt threads and install bolt. Tighten crankshaft pulley bolt to specification.

7. Rotate crankshaft about 5-6 turns clockwise to position timing belt on pulleys. Ensure crankshaft and camshaft pulleys are aligned at TDC. Crankshaft pulley White mark should be aligned with pointer on front cover. Remove rubber plugs from upper covers to check camshaft pulley positions.

8. If either camshaft is not at TDC, remove timing belt and readjust position. To complete installation, reverse removal procedure. Tighten all fasteners to specification. Adjust drive belts to proper tension.

Installation (Used Belt)
1. Ensure that engine is at TDC. Align dimple on timing belt drive pulley with pointer on oil pump. See Fig. 4. Align camshaft pulleys with pointers on back covers.

2. Apply liquid thread lock to idler pulley bolt, and loosely install idler pulley. If auto-tensioner has extended and timing belt cannot be installed, perform new belt installation procedure. If auto-tensioner has extended and timing belt cannot be installed, remove and compress auto-tensioner. Install auto-tensioner.

3. Install timing belt in counterclockwise direction in the following sequence:
Crankshaft pulley, idler pulley, front camshaft pulley, water pump pulley, rear camshaft pulley and tension adjust pulley. See Fig. 7. Ensure crankshaft and camshaft pulleys remained aligned with marks on back cover. Tighten idler pulley bolt to specification.

4. Remove battery clamp bolt from back cover. Install engine mount bracket to the front of engine. If applicable, install timing belt guide plate with concave surface facing out. Install lower cover, then upper front and rear covers. Clean, then install crankshaft pulley. Lubricate crankshaft pulley bolt threads and install bolt. Tighten crankshaft pulley bolt to specification.

5. Rotate crankshaft about 5-6 turns clockwise to position timing belt on pulleys. Ensure crankshaft and camshaft pulleys are aligned at TDC. Crankshaft pulley White mark should be aligned with pointer on front cover. Remove rubber plugs from upper covers to check camshaft pulley positions.

6. If either camshaft is not at TDC, remove timing belt and readjust position. To complete installation, reverse removal procedure. Tighten all fasteners to specification. Adjust drive belts to proper tension.

Please let us know

Cheers,

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Tuesday, January 18th, 2011 AT 1:07 PM
Tiny
RAUL DR
  • 2004 HONDA ODYSSEY
  • 3.8L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 20,021 MILES

The heater in my car car just blows cold air. Do you have any idea what it could be?

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Monday, April 24th, 2017 AT 10:22 AM (Merged)
Tiny
STEVE W.
  • EXPERT
  • 4,197 POSTS

Check the heater hoses leading to the core. Both should feel hot to the touch with a warm engine. They connect to a control valve that opens/closes to allow coolant through. If it is bad you get no heat. If both are warm and the valve opens, then it is likely to be the air mix door or it is actuator that are faulty and not directing the air through the heater core.

The air mix door and motor are under the heater plenum toward the floor in the passenger foot well. You can watch it as you select hot/cold. If the linkage is moving but no heat it is probably a bad door, if the linkage is not moving it is a bad motor.

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Monday, April 24th, 2017 AT 10:22 AM (Merged)
Tiny
FRANXUA1
  • 2004 HONDA ODYSSEY
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 100,000 MILES

My 2004 honda odyssey heater wont heat, neither the front or the back! I changed the thermostat, I purged the system, I changed the cabin air filter and still no heat, the door that changes the settings from hot to cold works fine too, and also the fans start working too soon. Any ideas on what it could be?

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Monday, April 24th, 2017 AT 10:22 AM (Merged)
Tiny
HONDAMIKE
  • MEMBER

Check to see if the hose going out of the heater core is hot. If not, you have a plugged heater core.

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Monday, April 24th, 2017 AT 10:22 AM (Merged)
Tiny
FRANXUA1
  • MEMBER

I checked that too, the heater core is fine! Its driving me crazy, I cant think of anything else!

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Monday, April 24th, 2017 AT 10:22 AM (Merged)
Tiny
JACOBANDNICKOLAS
  • EXPERT
  • 68,429 POSTS

IF you have hot coolant going through the heater core, then the blend door has to be the problem.

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Monday, April 24th, 2017 AT 10:22 AM (Merged)

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