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3-Series (E36) Chat relating to the BMW 3-Series from 1992-1999. Autodoodad Specific models include: BMW 316i, BMW 318i, BMW 318iS/ti, BMW 320, BMW 323, BMW 320, BMW 324, BMW 325, BMW 328.

 
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#1 (permalink) Old 11-04-2004, 10:11 PM
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When i turn on the heat on my car on defrost the heat comes out just fine, but when i flip it over to head/chest level vents it turns cold....(btw, it used to work)

Anyone experience this?

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#2 (permalink) Old 11-04-2004, 10:14 PM
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Quote:
Originally posted by _1634_@Nov 4 2004, 09:11 PM
When i turn on the heat on my car on defrost the heat comes out just fine, but when i flip it over to head/chest level vents it turns cold....(btw, it used to work)

Anyone experience this?
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#3 (permalink) Old 11-05-2004, 05:29 PM
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Quote:
When i turn on the heat
yes, the heat was all the way up...(it was putting out heat out the defrost vents right before i switched it over to head/chest level)

any thoughts?

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#4 (permalink) Old 11-06-2004, 12:56 PM
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some air directing flaps seem to be messed up.

when I turn on my defrost, I hear a loud "PATHUNK", I know somethings ether stuck or something, but it works fine, I oughta fix it before I re-sell it.


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#5 (permalink) Old 11-06-2004, 01:38 PM
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on mine, the duct that goes from the heater to the vent system (defroster, vents, you name it, nothing works) is loose. Now the center console heats up like a bitch when the heater's on.


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#6 (permalink) Old 01-04-2005, 08:54 AM
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Quote:
some air directing flaps seem to be messed up.

when I turn on my defrost, I hear a loud "PATHUNK", I know somethings ether stuck or something, but it works fine, I oughta fix it before I re-sell it.
opens imaginary edmunds manual....

damn it...

makes sense.

anyone encountered this problem?

i think i hear the "PATHUNK" too, i forget what does it on my car...


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#7 (permalink) Old 01-04-2005, 10:42 AM
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left of center (drivers side) if one of these valves goes bad it causes either the heat at the floor or dash, or defrost to stick either in the full on, or full off position. There is a write up somewhere on this forum or ultimateBMW.com on how to check/replace the valve. Costs less than $100 and fixed my problem. Remember to bleed the cooling system after you change out the valve
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#8 (permalink) Old 01-04-2005, 11:45 AM
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Somehow left the first sentence of my previous post off. Should read:

On the E36 there is a duel valve heater control valve mounted to the firewall just to the left (drivers’ side of engine……
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#9 (permalink) Old 01-04-2005, 03:09 PM
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Quote:
when I turn on my defrost, I hear a loud "PATHUNK", I know somethings ether stuck or something, but it works fine, I oughta fix it before I re-sell it.
I used to hear that same noise when I turned the heat on and off...I then replaced the final stage...all is good

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#10 (permalink) Old 01-04-2005, 03:41 PM
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i have that same noise.

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#11 (permalink) Old 01-05-2005, 05:16 PM
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Time out! May be a simple thing!!

There are two control wheels on the center air vents. One to turn them on/off and one to change from hot to cold air when the heat is on. Make sure that wheel is turned toward the red and not the blue.

Let us know your results.

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#12 (permalink) Old 01-05-2005, 06:31 PM
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i understand what you are saying, but maybe i didnt make myself clear on the first post...

this is what it is doing...

heat on, (both passenger and driver) both smaller knobs all the way on the red (max heat)

frontal defrost on.... heat....

turn only the directional knob from front defrost to either feet or face...

room temp air...


im baffled.

(and no, it hasnt always done this, so i know somthing has changed.) ill try to fiddle with it today.

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#13 (permalink) Old 01-05-2005, 06:59 PM
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I hear ya...even though both temp knobs turned to red all the way, check the wheel below (above?) the middle heat vents and make sure that that is ALSO turned to the red.

<span style='color:green'>1994 325i </span>- - - 75,000 mi.
No mods - - - very happy as is!
<span style='color:green'>1995 525i </span>- - - 154,000 mi.
No squeaks or rattles... unreal!
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#14 (permalink) Old 01-18-2005, 06:21 PM
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Quote:
Originally posted by frank3@Jan 5 2005, 06:59 PM
I hear ya...even though both temp knobs turned to red all the way, check the wheel below (above?) the middle heat vents and make sure that that is ALSO turned to the red.
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it might be two problems. One
the heater valve on the engine compartment got stuck, clogged or simple died. get one on ebay replace it.
The other possibility.

Depending if you have the manual or electronic ac, there are several electric motor to open and close flaps inside the heater box, i know this because i use to have this issues and so i took the dashboard out and cleaned and lubricated all moving parts and electrical plugs...
For the manual ac control, bmw uses 3 servo motors, as they are called. one to close the blower housing, this motor is on the inside, but it closes the flaps outside the blower ousing to prevent things going into the blower when not in use.
the other 2 are responsible for directional, they direct where the flow goes inside the cabin, up down, chest.. etc.

I don't think the motors are shot, since they are very strong. would recommend unclipping them from the heater box, and moving the dials and see if they turn
just open the bottom panels on the dashboard and look for little round metal thing with 2 wires on it. the motors are held in there by clips.
try different settings and see if the turn, then try to turn the axle the motor is suppose to move and see if its free.

On the electronic ac, there are 5 motors. just follow the same procedure.

But as experience, this servo motors are very hard to fail, and so the flap inside the heater box. when i took the dashboard out on my car, all flaps where very free to move and the motors moved fine.
What does happens on this bmw's as they get old is that the electrical plugs create resistance because of rust., humidity.
since many temperature sensors and servo motors work on resistance to inform temperature or position, the ac control unit gets wrong readings.

yes it sounds complicated, but is not.. just take you time under there.

Remember that on this car, resistance is used to inform the computer a temperature value or position, this applies for sensors on the ac system. to sensors on the engine, the only difference on the engine is that the air mass sensor uses a thin heated wire to inform mass based on how much current the system draws in order to maintain that same temperature as air goes by.
Many problem with this cars is not the control unit, normally is it rusted of malfunctioning wire plugs, so just taking them out and replugging helps. and also sensors that fail.

hope this helps.

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