Question about Audi A4
Hi, you mentioned your hoses are cold. Are those the evaporator hoses or heater hoses? The evaporator hoses are usually made of aluminum, whereas the heater hoses are rubber. It is normal for the evaporator lines to be cold. If the heater hoses are cold, assuming the engine is warm and your thermostat is not stuck open, you either have an air bubble blocking the flow of coolant to the heater core or the core is clogged. To release an air bubble, park on an incline, open the radiator cap, run the engine until the thermostat is open, crack open any/all bleed ports to release any trapped air, and fill the radiator to the neck. Wait until the level stops dropping and make sure bubbles don't continue to come up. If they do, you may have a blown head gasket that will keep forming these bubbles until you change the gasket.
If your heater hoses are still cold after purging air, and there are no bubbles coming up, your heater core is likely to be clogged. You can try to unclog the core by removing the hoses at the firewall and attaching a garden hose to the lower port by splicing with a hose and clamps. If pressurizing the lower port with water will not unclog the core sufficiently, it will have to be replaced. This is a major repair requireing removal of the dash panel and disconnect of the air conditioning system.
If your heater hoses are hot and only cold air comes out of your heater, the problem is with the heater blend door. Not sure if your blend door is motorized or uses a cable. The actuator is either on the bottom or top of the heater box shown below. Check to see if the door actuates when you change the temperature setting. If not, remove the actuator and check the door manually. Make repairs as necessary.
Please let me know if you have any questions, and thanks for using FixYa.
Posted on Jan 02, 2011
I had this issue a while back, my problem was the fuse for the heater had melted, very starnge but I have since seen this fault on numerous A4's I would check that first. the Aircon would not blow constant and it still would not effect the hot air coming out. Diagram below
That may not be the fault but worth looking at first, secondly the resister for the heater may have blown this can happen after a cold spell.
Hope this helps, if you need more specifics please get back to me.
Posted on Jan 01, 2011
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Posted on Jan 02, 2017
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