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The Audi Doctor
The Audi Doctor, Technician
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Experience:  Over 30 years experience, 17 years with Audi, Factory trained
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Hi, I have a 2000 jag. S-Type v-6, 3.0 and the heater dosent

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Hi, I have a 2000 jag. S-Type v-6, 3.0 and the heater dosen't will blow air out the vents but no heat. the air- cond. works when it on. Think it might be the daul climate control value or maybe some call it the heater value. I,m not sure how to test to determan what it is.

Thank You for choosing Just Answer and for your query. Yes, I can help you.

Does the engine temperature gauge get up to normal operating temperature? It should be straight up, or half way. If not the thermostat is stuck open or opening to soon and must be replaced.

If the engine temperature is correct your symptoms are consistent with a plugged heater core or possibly a failed dual coolant flow valve.

The core of the heater core is not only a group of tubes, but the tubes are filled with a mesh material similar to steel wool. It takes very little resistance to overcome the low pressure from the engine. On a properly functioning system the temperatures of the two heater hoses is typically fairly close with only a slight reduction in temperature. Typically when I replace restricted heater cores the coolant often appears perfectly clean. When I cut open the core and then it has a chance to dry out, small particles consistent with the appearance of sand are found in the mesh material.

The amount of flow going through the heater core is very hard to determine and the apparent resistance can be deceiving. If you try and remove the heater hoses and check for flow, you will not be able to determine the “flow” as the coolant is “drawn” (sucked) through the core by the water pump. This way there is flow through the heater core even before the thermostat has opened. If you run water through the core or blow through it, it may appear not to be restricted, again “deceiving”.

I suggest you try to confirm the core blockage as follows. Fully warm the engine to operating temperature. With the temperature set to maximum heat shut off the fan so that no air flows through the system. Drive the vehicle at slow speeds or run at an elevated idle for a few minuets. Turn on the defrosters at maximum heat and turn the fan on high. If the heat appears hot at first, but then rapidly diminishes, the core is likely the cause. If however there is no heat the dual coolant control valve may be at fault.

The dual coolant valve regulates the flow of engine coolant to each half of the heater core. Two electric solenoids, Which are individually actuated by the heater control module, are the control elements. The valve contains five ports:

inlet port - coolant from the engine

outlet port - coolant to driver side of heater core

outlet port - coolant to passenger side of heater core

return port - common coolant return from heater core

outlet port - coolant return to engine

The next step would be to remove the valve and check for flow restriction. Would this be within your capabilities? Or are you just looking for a better idea of what might be going on before you bring it into the shop?

If there does appear to be a restriction in the heater core to further confirm, you can try back flushing (flushing backwards) the heater cores with a water hose. Observe the expelled water, especially in the beginning, for any evidence of contamination. Use a clear hose that you buy from the hardware store and run the fluid into a clean bucket. This may give you increased performance, but typically will not be 100%.

I hope I have answered your questions and addressed your concerns. Should you have further questions on this matter, please do not hesitate to ask. I want you to be 100% satisfied with my answer.

Positive feedback, referrals and bonuses are always APPRECIATED. Please rate my answer as OK, GOOD, or EXCELLENT. With a lower rating I will not be compensated. Please contact me with your concerns if you cannot rate my answer OK, GOOD or EXCELLENT.

Thank You!
Jake “The Auto Doctor”
The Audi Doctor and 6 other Car Specialists are ready to help you
Customer: replied 4 years ago.

you have given very good feed back. The tempature of the engine is good. I have driven it all summer like that. The defrost never has any heat from it and I'm really thinking it's going to be the dual control value. The only other thing I though of was the control vent AC flap Actuator stuck open. I can change the value, but not sure if there are bleed ports to get the air out of the system.

Now that you know it's not a plugged heater core, the Coolant valve is the likely cause. Odds are that if you change it it will likely correct the condition. The valves sell for about $300 and a shop would likely charge two hours labor to replace it. I believe on the 3.0L engine vehicles the A/C receiver/dryer will need to be removed to access it. This means evacuating, and charging the A/C system. This may be better left to a pro as without the A/C service machine you can not properly service the system and the A/C will not function properly thereafter. Here is the bleeding explanation you requested.

  • Open the engine air bleed located on the engine crossover pipe.
  • Open the heater air bleed located on the expansion tank.
  • Fill the expansion tank until the coolant flows from the engine air bleed screw and expansion tank is full.
  • Close the engine air bleed screw.
  • Install the expansion tank cap.
  • Leave heater air bleed open.
  • Start the engine and set the heater to29°C/ 90°F temperature.
  • Close heater air bleed when a steady stream of coolant flows during engine idle.
  • Allow the engine to idle for 5 minutes, adding coolant to the expansion tank to maintain the COLD FILL MAX level.
  • Open the heater air bleed to release any trapped air, close the heater air bleed.
  • Increase the engine speed to 1500 rpm for between three and five minutes or until the heater is blowing hot air.
  • Return to idle and verify that heater is blowing hot air.


I have a pretty busy day today and don't know if I will be able to get back to you till tomorrow, at which time I can answer any further questions.


Positive feedback, referrals and bonuses are always APPRECIATED. Please rate my answer as OK, GOOD, or EXCELLENT. With a lower rating I will not be compensated. Please contact me with your concerns if you cannot rate my answer OK, GOOD or EXCELLENT.


Thanks Jake