Heater Not Working Properly

Tiny
LEAHB
  • MEMBER
  • 2005 AUDI A4
  • 4 CYL
  • FWD
  • AUTOMATIC
  • 18,000 MILES
My heater gets hot during high RPM and cools off during idle. I had the thermostat changed last week and it did not correct the problem. Can you suggest what needs to be done?
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Wednesday, December 3rd, 2008 AT 8:33 AM

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Tiny
IMPALASS
  • MECHANIC
  • 3,112 POSTS
Hello

First I need a little more specific on your vehicle to better assist you. Is your model just an A4, or A4 Cabriolet, A4 Quattro Cabriolet, A4 Quattro Sedan, A4 Quattro Wagon, A4 Sedan, A4 Quattro only? Also what is your engine size in liter and the 8th digit of your VIN.

Next, at idle normal operating temperature are the heater hoses going into the firewall both hot or only one?

When the RPM is raised, same question, are the heater hoses going into the firewall both hot or only one?

Has there been anything wrong with your engine temperature at all?

And again, you started having this heater problem "then" you changed the thermostat and you still have the problem?

Do you have Dex-Cool or another brand of antifreeze in your vehicle?

This guide will help us

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

Please answer/do the above and get back with me and let's see if we can get you some steady heat.
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Thursday, December 4th, 2008 AT 7:08 AM
Tiny
LEAHB
  • MEMBER
  • 2 POSTS
*Vehicle Info: A4 1.8T, 4 Door CVT Automatic.
*8th digit of VIN is E.
*Nothing wrong with engine temperature.
*I changed thermostat after having this problem.
*Car has 18,000 miles.
*I use Audi G12 antifreeze in car.
*At idle only one hose is hot.
*When RPM raised both hoses get hot.
*My engine light is not on. I called Auto Zone and they told me they can't pull the codes if the engine light is not on.
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Thursday, December 4th, 2008 AT 8:39 AM
Tiny
IMPALASS
  • MECHANIC
  • 3,112 POSTS
Hello - LeahB

Wow, thanks for the outstanding update/information. We don't always get the info we ask for so detailed.

Okay, just a few things based off of what you have said.

First, there is a Technical Service Bulletin (TSB) out on a similar thing. I have attached that for your review. It actually states: "Customer concern of no heat or noticeable drop in heat output in passenger compartment from HVAC system when engine at idle" This is due to the plastic plug as shown. I put the TSB at the end of this.

Next - on the pic below there are two hoses between numbers 1, 2, 13. At idle, is the hose between 1 and 13 the one that is hot and 1 and 2 the one that is cool?


https://www.2carpros.com/forum/automotive_pictures/248015_125787940_1.jpg



I would first check the plug that the TSB talks about. Even try and replace and see what you have.

Next - I would back flush the heater core. If that doesn't work then you may have to replace the core.

I am hoping it is just the plug from the TSB and worst case, a back flush if not the plug.

You don't have a lot of miles - that is about 6,000 a year. . .not much driving.

Looks like you may have some recalls on your vehicle. The dealer may fix these for free. Please contact the dealer service department, give them the VIN number of your car and have them check on these to see if they apply to you. I have attached those at the end.

Last, for Auto Zone etc. . .sometimes your car can throw a code, the light flash and go out. You might consider that when talking to them in the future.

19 07 01

March 26, 2007

2009949/3 Supersedes Technical Service Bulletin Group 19 number 05-03 dated Apr. 8, 2005 due to revision of a part number.


https://www.2carpros.com/forum/automotive_pictures/248015_1_100.jpg



Vehicle Information

Coolant Leak or No Heat in Passenger Compartment From HVAC

Condition

Coolant Leak or No Heat in Passenger Compartment From HVAC System

Technical Background


https://www.2carpros.com/forum/automotive_pictures/248015_2_65.jpg



Customer concern of loss of coolant, but no leak in cooling system can be found.

Customer concern of no heat or noticeable drop in heat output in passenger compartment from HVAC system when engine at idle.

Both concerns may be caused by a coolant leak from plastic plug.


https://www.2carpros.com/forum/automotive_pictures/248015_3_48.jpg



Plug is installed in engine cylinder block near connection for thermostat housing (arrow).

Improved Coolant Plug.

Service

Other than loss of coolant, a leaking plug can cause air to enter into the cooling system and reduce the effectiveness of the passenger compartment heating system.

Cooling system MUST be tested for leaks with engine cold (below 32 °F / 0 °C) (see ElsaWeb Repair Manual, Engine Mechanical, 19 Engine Cooling, " Cooling system, checking for leaks ").

Tip:
The leak from this plug usually occurs only when the engine is cold (below 32 °F / 0 °C).

If cooling system is tested for leaks with engine warm or hot:

Leaks from this plug may not be detected.

Tip:
Coolant leak from this plug can be sometimes misdiagnosed as a leaking coolant thermostat housing. Always carefully inspect suspected areas to detect the actual source of the leak.

Carefully inspect area where plug is located.

If the plug is found to be leaking:

Remove and replace the plug. Required Parts and Tools

Remove sound insulation below engine.

Drain coolant (see ElsaWeb Repair Manual, Engine Mechanical, 19 Engine Cooling, " Cooling system, draining and filling").

Remove upper engine cover.

Unfasten coolant reservoir and move to aside.

Electrical connector of coolant level sensor must be unplugged.

It is not necessary to remove coolant hoses from coolant reservoir.

Remove oil dipstick bracket bolts (2x).

Carefully remove upper dipstick tube (orange plastic)

Ensure that the O-ring on lower steel tube is not lost when tube is removed).

Remove bolt from plastic plug.

Remove plastic plug from engine block .

Install a new plastic plug and secure with bolt to engine block.

Fastener torque = 23 Nm.

Reassemble dipstick tube and coolant reservoir.

Use the VAS 6096/1 to refill and bleed the cooling system (see ElsaWeb Repair Manual, Engine Mechanical, 19 Engine Cooling, "Cooling system, draining and filling" for details and approved coolant antifreeze).

When refilling engine with coolant:

Always ensure that any trapped air is bled out of cooling system (including heater core).

Recheck for leaks on cooling system (see ElsaWeb Repair Manual, Engine Mechanical, 19 Engine Cooling, " Cooling system, checking for leaks").

Reinstall sound insulation below engine.

Reinstall upper engine cover.


https://www.2carpros.com/forum/automotive_pictures/248015_4_28.jpg



Warranty

Required Parts and Tools

Plug - Part No: 06B 103 033 A

Tip:
Part numbers listed in this bulletin are for reference only. Always check with your Parts Dept. for the latest parts information.


https://www.2carpros.com/forum/automotive_pictures/248015_Picture2_21.jpg

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Thursday, December 4th, 2008 AT 7:10 PM
Tiny
LVMORA
  • MEMBER
  • 1 POST
Hello carpros.

I'm having the same issues as stated above. No heat in idle and some heat during hi RPMs. Im not sure if the plug has been changed in this car.

Hose between 13 and 1 is hot. Hose between 1 and 2 is not.

I did flush the heater coil already.

Please any advice will be greatly appreciated.

Lvmora
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Sunday, December 13th, 2015 AT 12:26 PM
Tiny
LEW.FAMILY
  • MEMBER
  • 1 POST
  • 2001 AUDI A4
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 113,000 MILES
I have a 2001 Audi A4 that the heater is not working. I've adjusted the temperature up/down and I can hear solenoid/valve/door moving. That tells me that the electronic temp. Controller is probably working. Do I have a bad heater core or is there something else wrong?
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Thursday, May 7th, 2020 AT 12:45 PM (Merged)
Tiny
JRT
  • MEMBER
  • 27 POSTS
Is the radiator full of coolant?
Are the heater hoses going to the heater core hot at the firewall?
If they are not then the thermostat is stuck open. If the inlet hose is hot and the outlet hose is cold or luke warm, then the heaer core is stopped up.
Hope this helps.
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Thursday, May 7th, 2020 AT 12:45 PM (Merged)
Tiny
DIRT_BIKERT
  • MEMBER
  • 1 POST
  • 1998 AUDI A4
  • 6 CYL
  • AWD
  • AUTOMATIC
  • 74,000 MILES
Hi,
My car doesnt blow any hot air. The air conditioning works and when I turn the heaters on they blow hot air for about 30 seconds and then it blows cold air. Any idea wats going on?
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Thursday, May 7th, 2020 AT 12:47 PM (Merged)
Tiny
DOCFIXIT
  • MECHANIC
  • 18,828 POSTS
Your system is Automatic Temp Control and is somewhat complex. Needs to be hooked up to a scanner to diagnosis system.
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Thursday, May 7th, 2020 AT 12:47 PM (Merged)
Tiny
DLOGAN
  • MEMBER
  • 1 POST
  • 1998 AUDI A4
My 1998 A4 has 105,000 miles. My thermostat was stuck open - evidenced by the lack of heat in passenger cab and the constant cold temperature reading on engine coolant gauge. I just got the thermostat replaced and now have normal readings on the engine temperature gauge. However, I still do not have any heat available in the cab. Anti-freeze levels are OK. How can I determine if the problem is related to the heater control value, vacuum check value, blend door or other?
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Thursday, May 7th, 2020 AT 12:47 PM (Merged)
Tiny
BRUCE HUNT
  • MECHANIC
  • 3,753 POSTS
Follow the heater hose from the thermostat housing to the firewall and locate the return hose. Is the return hose cold? Is the supply hose warm, hot, or cold? If warm or hot follow it to a valve and feel the opposite side of temp. Your system may not be so simple but it should have a hot hose to the heater. If it is hot both in and out the damper door on a plenum is not opening.

Make sure as well that there is no air in the cooling system.
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Thursday, May 7th, 2020 AT 12:47 PM (Merged)
Tiny
GARYVEEVERS
  • MEMBER
  • 4 POSTS
  • 1998 AUDI A4
  • 177,000 MILES
Help i've bought a car with no heating, seller says he bought it also with no heater so have no history on how it went or why. Its an audi a4 avant 1.9tdi estate 1998 (b5). A/c pump has gone but also have no heater, blows out cold air. Have bled the system for ages getting the air out, temp goes steadily to 90 most of time but occasionally drops suddenly. Top hose from radiator goes red hot all the time but bottom hose isnt as hot.I know the a/c pump has gone but i've checked thermostat; brand new, changed head gasket, timing belt, still nothing. Vag-com results say too many errors (excessive comm errors) on channel 08; auto hvac. Altered density etc, but cannot get any fault codes for this code number however I try. Only found errors on channel 35; centr. Locks.16 in total, 7 of these were unknown error codes.
Any ideas?
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Thursday, May 7th, 2020 AT 12:47 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,005 POSTS
With the engine running, hot, and the heat on high, feel both heater core hoses. Both should be hot. If only one is hot, try flushing the heater core. If both are hot, check the blend air door for operation.
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Thursday, May 7th, 2020 AT 12:47 PM (Merged)
Tiny
GARYVEEVERS
  • MEMBER
  • 4 POSTS
Both are hot, where is the blend air door? We've found loads of flaps and all seem in good condition
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Thursday, May 7th, 2020 AT 12:47 PM (Merged)
Tiny
RIVERMIKERAT
  • MECHANIC
  • 6,110 POSTS
Slowly move the temperature control back and forth with the engine running and heater on. Watch for actuators and levers moving on the airbox under the dash.
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Thursday, May 7th, 2020 AT 12:47 PM (Merged)
Tiny
GARYVEEVERS
  • MEMBER
  • 4 POSTS
Everything ok there. Tried flushing it through with a hose but it just blows the ends off. Loads of shiny coppery bits in what came out but it did help a bit as the car now has a bit of heat coming out now. Read online it sounds like copperseal which was probably used as a quick fix gone wrong as I did the head gasket when I got it. Trying some caustic soda and warm water in hose to try and blow it through rather than taking whole car apart again. Will let you know if that finally fixes things for me.
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Thursday, May 7th, 2020 AT 12:47 PM (Merged)
Tiny
WEBOMAN
  • MEMBER
  • 2 POSTS
  • 1997 AUDI A4
Heater problem
1997 Audi A4 6 cyl All Wheel Drive Manual 130k miles

There is very little heat coming out of the dash vents as well as the defrost vents. I am not really sure of where to begin. The thermostat seems to be working and there seems to be coolant circulating through the system. The inlet and outlet tubes at the heater core seem to be hot. Any suggestions of where to begin?What is the layout of the system? Is this care prone to a specific problem with the heater core, thermostat, air mix door?
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Thursday, May 7th, 2020 AT 12:47 PM (Merged)
Tiny
MASTERTECHTIM
  • MECHANIC
  • 4,749 POSTS
I imagine coolant level is ok. Coolant gauge on dash read normal? Can you hear the blend door moving when switching from hot to cold?
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Thursday, May 7th, 2020 AT 12:47 PM (Merged)
Tiny
RIVERMIKERAT
  • MECHANIC
  • 6,110 POSTS
You may end up having to pull the airbox out from under the dash and put in a new heater core. Let us know what happens. We'll be here.
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Thursday, May 7th, 2020 AT 12:47 PM (Merged)
Tiny
WEBOMAN
  • MEMBER
  • 2 POSTS
Coolant level normal, air blend door working, temp on gague moves.
Any other Ideas? :
BTW I have made a donation under a diffrent email.
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Thursday, May 7th, 2020 AT 12:47 PM (Merged)
Tiny
GARYVEEVERS
  • MEMBER
  • 4 POSTS
Ok, update; done matrix, still no better on heater. Radiator bottom hose stone cold. Thinking blocked waterways on actual engine or maybe dodgy new thermostat? Help
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Thursday, May 7th, 2020 AT 12:47 PM (Merged)

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