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Discussion Starter · #1 ·
Bought a new aux fan and thermo switch. checked all fuses. I can jump the leads on the fan to get it to turn on, both of them actually. Still nothing works. Checked the RC134 level and topped it off. also fan is spinning clockwise in front and slows down the radiator fan when it spins, making the radiator fan practically stop. dont think thats normal. A/C also doesn't blow cold but still blows otherwise. Trying to back track all the wiring and see if anything is burnt. but it all looks good so far.

TL;DR

Automatic 323i 2000
 

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http://i.imgur.com/9Cs4Q.jpg

found this piece not connected to anything. could this be a problem??

I want to say that looks like the thermostat, which is what I thought you meant by "thermo switch" in your original post. I've never had mine out, to confirm, but that connector sure looks right.

If so, then I would say yes, that could be a problem. I'm guessing that means the new one is not connected to anything?
 

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Discussion Starter · #8 · (Edited)

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It's the ambient air temperature -- it controls the climate control in the car. It might affect aux fan if it's not connected to the wire. The car will default to -40F ambient air temperature if not connected so it will think it doesn't need to blow the A/C.
 

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Discussion Starter · #11 ·
It's the ambient air temperature -- it controls the climate control in the car. It might affect aux fan if it's not connected to the wire. The car will default to -40F ambient air temperature if not connected so it will think it doesn't need to blow the A/C.
It is connected at the other end of the switch, but I was under the impression that thing just sits under the car anyways. I live in Florida and its always hot, but my car never goes past 12' O clock for the radiator temp. Even with only 1 fan going.

pretty sure the ambient temp switch goes here:

http://i.imgur.com/0XiIZ.jpg
 

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The coolant temp gauge will read in the middle at coolant temps in the engine from about 167 F to 235F.
The outside (ambient) temperature sensor is not used to control of the engine cooling fan(s)



Coolant temperature gauge
The indicator characteristics of the coolant temperature gauge in the instrument cluster have been adapted to the higher temperature level of the engine due to the use of the characteristic map thermostat.
The pointer of the coolant temperature gauge in the instrument cluster is located in the mid-position at coolant temperatures of
75C - 113C in centre position.
 

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I agree with you shanneba but I'm pretty sure the auxiliary fan kicks on when then A/C is used. I believe the ambient temperature sensor will tell when to kick on the auxiliary fan if the A/C does use the aux fan.

The temperature sensor is mounted under the car in the brake cooling duct, on the drivers side, inside the bumper.
 

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Discussion Starter · #14 ·
The fan is controlled by the main ECM after getting input signals from: the electrically heated thermostat, the radiator outlet temp. sensor, the catalyst calculated temp., the vehicle speed, A/C pressure and the battery voltage. Where is this electrically heated thermostat?

Yes the fan will come on with A/C use but mine never does. Also it should come on for about 15 seconds when I crank the car. What is the possibility of 2 bad fans that work when you jump the leads?

I'm running out of ideas on this one. I'm going to buy a voltmeter now to see if I can test the wiring.
 

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I agree with you shanneba but I'm pretty sure the auxiliary fan kicks on when then A/C is used. I believe the ambient temperature sensor will tell when to kick on the auxiliary fan if the A/C does use the aux fan.

The temperature sensor is mounted under the car in the brake cooling duct, on the drivers side, inside the bumper.
The Ambient temp sensor is not used to control the cooling fan.
The fan may not run when the A/C is switched on.


See page 31 of this link for fan info from BMW: http://www.beisansystems.com/misc/SEIMENS_MS_420_ENGINE_CONTROL_SYSTEM.pdf

ELECTRIC FAN
The electric cooling fan is controlled by the ECM. The ECM uses a remote power output final stage (mounted on the fan housing)
The power output stage receives power from a 50 amp fuse (located in glove box above the fuse bracket). The electric fan is controlled by a pulse width modulated signal from the ECM.

The fan is activated based on the ECM calculation (sensing ratio) of:
• Coolant outlet temperature
• Calculated (by the ECM) catalyst temperature
• Vehicle speed
• Battery voltage
• Air Conditioning pressure (calculated by IHKA
and sent via the K-Bus to the ECM)


Activation of the electric fan:
When the vehicle is first started the fan is activated briefly (20% of maximum speed), then
it is switched off. This procedure is performed for diagnostic purposes.
The voltage generated by the fan when it slows down (it becomes a generator at this time)
must meet the power output stages programmed criteria. This will confirm the RPM of the
fan, if this is not met the signal wire from the output stage is switched to ground and a fault
is set in memory.
NOTE: If the ECM indicates a fault check the fan for freedom of movement
After the initial test has been performed, the fan is brought up to the specified operating
speed. At 10% (sensing ratio) the fan runs at 1/3 speed. At a sensing ratio of between 90-
95% the fan is running at maximum speed. Below 10% or above 95% the fan is stationary.
The sensing ratio is suppressed by a hysteresis function, this prevents speed fluctuation.
When the A/C is switched on, the electric fan is not immediately activated.
After the engine is switched off, the fan may continue to operate at varying speeds (based
on the ECM calculated catalyst temperature). This will cool the radiator down form a heat
surge (up to 10 minutes).
 
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