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E46 (1999 - 2006)
The fourth generation 3 Series (E46 chassis) was introduced in 1999 and set the standard for engineering and performance during it's years of production including being named to Car & Driver's 10 best list every one of those years! ! -- View the E46 Wiki

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  #1  
Old 10-22-2010, 01:55 PM
88keys 88keys is offline
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Location: NY
 
Join Date: Oct 2010
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Mein Auto: 2000 323i
Unhappy Intermittent Heat Issue ARGHH!

Hi, I'm a newbie and I've read through so many posts but none seem to nail my issue...
My 2000 323i (E46) runs like a top, but I have a strange heating issue:

Begin with a cold start (car has been off overnight, for example), and the heat comes on as it should, nice and warm.
Ride around, typically I do a lot of highway, but it seems not to matter if I'm at any consistent speeds: Heat SUDDENLY blows COOL, and stays that way forever and ever amen. EVEN if I shut the ignition off, and let it sit for even an hour (say)... the heat still blows cool.

I'd have to wait for a cold-start condition again, and then it's fine again... until it happens again.. and it happens ALWAYS with the above scenario. There is never a time when it continues to blow hot after even a half-hour of driving. After a half-hour or so, the cool air starts again.

NOW, at some point I used to flip the defroster on, and occasionally I'd notice the heat would SLOWLY come back through that system, and I'd flip it back to the floor (or middle) vents. It no longer will do that (at least, I've given it an inordinately long time to do so but so far even after several to 10 minutes, no success.

I have had the heater core replaced (other issues), the radiator, the thermostat, and the water pump as well! Still no difference.

My next step is to replace the module, which I just bought and am waiting for to get here.

Anyone have a clue?!?
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  #2  
Old 10-22-2010, 02:09 PM
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catso catso is offline
catso
Location: Chicago
 
Join Date: Dec 2009
Posts: 2,854
Mein Auto: 2000 323i, 1988 528e
Quote:
Originally Posted by 88keys View Post
Hi, I'm a newbie and I've read through so many posts but none seem to nail my issue...
My 2000 323i (E46) runs like a top, but I have a strange heating issue:

Begin with a cold start (car has been off overnight, for example), and the heat comes on as it should, nice and warm.
Ride around, typically I do a lot of highway, but it seems not to matter if I'm at any consistent speeds: Heat SUDDENLY blows COOL, and stays that way forever and ever amen. EVEN if I shut the ignition off, and let it sit for even an hour (say)... the heat still blows cool.

I'd have to wait for a cold-start condition again, and then it's fine again... until it happens again.. and it happens ALWAYS with the above scenario. There is never a time when it continues to blow hot after even a half-hour of driving. After a half-hour or so, the cool air starts again.

NOW, at some point I used to flip the defroster on, and occasionally I'd notice the heat would SLOWLY come back through that system, and I'd flip it back to the floor (or middle) vents. It no longer will do that (at least, I've given it an inordinately long time to do so but so far even after several to 10 minutes, no success.

I have had the heater core replaced (other issues), the radiator, the thermostat, and the water pump as well! Still no difference.

My next step is to replace the module, which I just bought and am waiting for to get here.

Anyone have a clue?!?
Did you bleed the cooling system properly? Maybe you have an air pocket in there. It helps to do it with the front end slightly higher than the rear. Sometimes you have to do it more than once to get all the air out.
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  #3  
Old 10-22-2010, 02:10 PM
ccagle ccagle is offline
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Location: Auburn,AL
 
Join Date: Sep 2009
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Mein Auto: 325I
It sounds to me like a thermostat issue? Sounds like at cold start, it's closed, creating the heat needed. Then after it opens up, it stays open not allowing it to creat the heat needed. Then after it cools and closes, it will have warm air again till it opens up........ Did you replace it with and oem temp range thermostat or something to make it run cooler?
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  #4  
Old 10-22-2010, 02:39 PM
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ahull ahull is offline
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Location: Carolina
 
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Mein Auto: ist schnell! (03 330i SC)
Maybe on the air pocket and maybe on the thermostat...... I'll venture a guess and sayit could be the heater water valve that routes water to the core. On my 330 it's mounted to the frame/strut tower under the intake tube/manifold connection.... has a couple 1 inch hoses going to/from it and is about the size and shape of two "C" batteries, IIRC. Either way, look for the hose that goes through the firewall and you can trace back to the valve.

Maybe try feeling the difference in temperature on the two hoses next time you get it up to operating temp with the heat set to "on" in the cabin. If one hose is hot and one is not then that's likely your culprit.

I'm thinking that even with a stuck open thermostat, the coolant would still get hot enough to provide heat.
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  #5  
Old 10-22-2010, 05:45 PM
88keys 88keys is offline
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Location: NY
 
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Mein Auto: 2000 323i
I've had it bled several times.. of course, it's possible that each time, it wasn't done right, but I kind of think that possibility has been exhausted!
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  #6  
Old 10-22-2010, 05:47 PM
88keys 88keys is offline
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Regarding the thermostat, I'm going to have that replaced as well... only lately has it been seeming to stick open (on the highway the temp gauge seems to be hovering left of center more than usual - but that's only a recent thing).
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  #7  
Old 10-22-2010, 05:50 PM
88keys 88keys is offline
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Location: NY
 
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Sorry about the mis-replies... I'll get the hang of it...

I wasn't aware of "heater water valve"! I'll have that checked as well... hopefully they don't have to pull the dash off to check it!
I'll also look into the temp difference of the hoses...
Winter is coming, I gotta get this thing figured out!

Thanks everyone!
J

Last edited by 88keys; 10-22-2010 at 05:51 PM.
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  #8  
Old 10-22-2010, 06:45 PM
e^2 e^2 is offline
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Location: Eugene Or
 
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Mein Auto: '84 325e, '00 323i
I had this exact problem. Ended up being the climate control fan. Problem it created was the heater would only work for a very short while and then it would blow cold air no matter what. And before that happened we could smell the slight smell of what was a burnt smelled like an overheating engine but was instead a toasted climate control fan. We got a used one for $150 and it's worked perfect ever since.
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  #9  
Old 10-22-2010, 06:52 PM
88keys 88keys is offline
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Location: NY
 
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The FAN? That is so strange, because it still BLOWS air... when you say it was the "fan", does that imply some other element integrated WITH the fan?? You see why I'm confused? )
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  #10  
Old 10-22-2010, 07:56 PM
e^2 e^2 is offline
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Location: Eugene Or
 
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Mein Auto: '84 325e, '00 323i
If you have climate control there is a fan that sucks the air into the vent sensors at the top by the sunroof controls, at the stereo, and down below. That's how it controls the air mixture and fan speed when it's at auto and stuff. Fan goes out, it has no idea what to blow.
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  #11  
Old 10-23-2010, 07:45 AM
88keys 88keys is offline
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Location: NY
 
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OK, thank you... I almost always run it on "manual", rather than auto (wonder if that negates the "need" for that function you are describing...) But I will check it out and post my result!
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  #12  
Old 10-23-2010, 12:30 PM
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catso catso is offline
catso
Location: Chicago
 
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Mein Auto: 2000 323i, 1988 528e
Quote:
Originally Posted by e^2 View Post
I had this exact problem. Ended up being the climate control fan. Problem it created was the heater would only work for a very short while and then it would blow cold air no matter what. And before that happened we could smell the slight smell of what was a burnt smelled like an overheating engine but was instead a toasted climate control fan. We got a used one for $150 and it's worked perfect ever since.
Where is this fan located?
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  #13  
Old 10-23-2010, 08:34 PM
e^2 e^2 is offline
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Location: Eugene Or
 
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Mein Auto: '84 325e, '00 323i
I think its behind the climate control center. Should be on the end of the vent tubes if you follow it in. I'll try to find a pic.
edit:
Might be in the unit. I didnt replace it cause I was out of town and the wife brought it in to the BMW repair shop and that's what they said thy did.

Last edited by e^2; 10-23-2010 at 08:52 PM.
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  #14  
Old 10-24-2010, 12:00 AM
mujjuman mujjuman is offline
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Location: NY
 
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Mein Auto: hoopty
Def replace your t-stat soon
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