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Old 03-20-2020, 12:50 PM   #1
Rainn
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Another heater issue

Hello guys. New owner here. I bought a 2004 bmw 330xi with about 240xxx miles on it with recent shop work and new clutch in it. I was driving to my parents house to check it out and I noticed once it started snowing my windows wouldn't defrost and the cab got colder and colder. I wandering if anyone may have some insight. The heater will only work somewhat decent if I'm driving. If I'm idle it will blow cold air. If I hit a bump will driving it will blow hot again.
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Old 03-20-2020, 07:09 PM   #2
dutchhome
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This is a pretty common problem. You should first make sure air is not trapped in the heater core. Find and follow directions on filling coolant to ensure you get all the air out.

If you are still having issues you may need to replace the final stage resistor (aka the hedgehog).

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Old 03-21-2020, 06:29 PM   #3
jmo69
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Quote:
Originally Posted by dutchhome View Post
This is a pretty common problem. You should first make sure air is not trapped in the heater core. Find and follow directions on filling coolant to ensure you get all the air out.

If you are still having issues you may need to replace the final stage resistor (aka the hedgehog).

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I agree with bleeding in case there is air but my thought is the T-stat is stuck open. The final stage resistor controls the heater fan speed not the temperature. There is the possibility that the heater control valve on the DS inner fender might by clogged and restricting flow. You should use the hidden menu to find the actual temperature of the coolant. it should be in the 93C range.
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Old 03-23-2020, 11:58 PM   #4
IdahoDoug
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Agree this is not a resistor problem, but the heater core not providing heat. I also agree there is air in the system and it needs to be properly bled as a first step. Be sure you are adding the same coolant as what is in the vehicle now. Might tell us what color it is as there is a factory type that is usually a certain color. As a separate comment - be sure you were not driving with the "recirculation" button pressed as that will cause the windows to steam up easily - no fresh air coming in the cabin. Speaking of that, I wonder if the cabin airflow is restricted from an old/plugged cabin air filter which you can replace easily in 10 minutes. A common previous owner neglect item.

But your main issue is to ensure there is no air trapped in your system and the bump sloshing hot water into the dashboard's heater core for a short time is an indicator this is your problem.
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Old 03-26-2020, 10:41 PM   #5
Rainn
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I appreciate all the tips and advice guys. Is there a perfect way to bled the system? Also im not sure where the hidden menu is that was said earlier.
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Old 03-28-2020, 09:13 PM   #6
jmo69
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You can google the hidden menu or try Youtube. The bleed method I use and has never failed me goes like this.
1. Try to raise the front end, either with ramps or stands.
2. Open the cap and bleed screw
3. Key on to position 2 car not running, heat set to high and fan on low.
4. Slowly fill the system until there is a steady bubble free stream of coolant
from the bleed hole.
5. install the bleed screw and adjust the level in the expansion tank so the top
of stick is level with the top of the tank.
6. Replace the cap, start the engine and let it warm up, keep a close watch on
the temp gauge, even better if you can access the temp on the hidden
menu.
7. Check for good hot heat from the vents.
8. If you have heat and no engine overheating go for a short ride to make sure
the temperature stays steady.
9. If everything is good let the car cool off completely, like overnight and check
the level in the exp. tank and adjust if necessary. Top of stick not above the
rim.
10. Repeat #9 till the level stabilizes.

While the engine is warming up in #6 you can rev it a few times and squeeze the radiator hoses to help move any air to the expansion tank.

Hope this helps. This is the hidden menu, #7 is what you want there's a list in the comments.
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Old 03-28-2020, 09:19 PM   #7
dutchhome
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By the way, it is very easy to overfill the coolant. If you do, it is more likely to cause early failure of the coolant system. Make sure that when you are done the float gauge is well below the max line while still poking out the top and bobbing up and down with the engine cold. Sometimes it makes sense to remove a little after bleeding but this typically isn't needed because the after it cools down the level goes down a bit.

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Last edited by dutchhome; 03-28-2020 at 09:25 PM.
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