I must admit my knowledge of climate control systems is limited. So I need some guidance on where to go in terms of diagnosis. Cold air works fine. But with roller on the air vent set all the way to full hot (3 red dots) the air is not heated at all but it is still blowing. Stranger yet, as I increase the temperature on the climate control unit in the dash, it blows weaker and weaker. When the temp on the dash is maxed (I think 32°C) there is no air coming out at all. I did notice today that if you decrease the temperature suddenly you do get warm air for about 10 seconds before it cools again. For that reason I suspect the heater valve is fine because there is at least some hot coolant getting to the heater core. Bad HVAC unit maybe?
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That is weird, is your coolant full? -
There might be a blockage at the heater core. There are a few threads on E46Fanatics that could help.Comment
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Yep, coolant is at the right level and bled. Temp guage is always at centre or slightly left of centre.Originally posted by cobra View PostComment
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Could be, thanks. Most threads on there seem to suggest its not bled properly so I'll bleed it again tomorrow and see what happens.Originally posted by Slideways View PostComment
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Turn on the cabin heater and check the input and output hoses at the heater valve to see they’re both hot. If yes then maybe the cabin air control flappers are not in right position.Comment
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If there's no air hot or cold with it set to 32C and the dial set to hot then the air side of heater core must be blocked. I wouldn't bother looking at coolant levels at this point. If it was a coolant issue it would at least still blow non heated air.Originally posted by Thoglan View Post
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Re-bled the system and got hot air blowing. It was short lived though and only seemed to blow when the car was revving slightly. At idle, still not really blowing. Seems there is air in the system still though as I am getting bubbling in the expansion tank when the car is on.Originally posted by Shonky View PostLast edited by Thoglan; 10-31-2021, 02:22 PM.Comment
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Kept bleeding it by revving it slightly with the front right corner jacked up until the bubbles stopped coming through at the expansion tank. I now have hot air coming through. Very strange. Must have been an air pocket at the heater core causing problems. Quite nice to have a problem easily fixed without throwing parts at it for a change. Thanks people.Comment
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Good job. As you said that both in and out hoses at the heater valve were hot, which means there was hot coolant flowing through the heater core, so why no hot air?Originally posted by Thoglan View Post
When you bleeding the air by watching bubbles in the tank, was the engine running at operating temp or it was still cold? I think reving up the rpm to 3000 rpm a few times helps moving the air into the tank.
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