[Abnob]

Hi, I have a question maybe someone can answer. My temp got to 103C and still, the fan had not turned on, I know it supposed to come on way before. I did a fan test with a diagnostic scanner and it works at 50% and 90%. My question is this: What sensor and where is it that gives the signal for the fan to work?
Thanks

[gbalthrop]

Originally Posted by Abnob

...My temp got to 103C and still, the fan had not turned on, I know it supposed to come on way before. I did a fan test with a diagnostic scanner and it works at 50% and 90%. My question is this: What sensor and where is it that gives the signal for the fan to work?
Thanks

INPA has an Activation Screen (F6 Activations, F2 E-Fan) that shows Actual Fan Speed as a % of Max.Speed, along with ECTS (Engine Coolant Temp Sensor) Temp and ROTS (Radiator Outlet Temp Sensor) Temp. If you are wondering WHY I'm talking about ROTS, see Bentley quote below.

That is essentially Top Radiator Hose Temp, and Bottom Radiator Hose Temp. If your model does NOT have the Radiator Outlet Temp Sensor installed in the Bottom Radiator Hose, INPA provides a "Calculated/ (faked ;-)" ROTS value which is EXACTLY 7.5C LESS than the ECTS Value, regardless of temp or engine conditions. Does your Scan Tool provide you with BOTH ECTS and ROTS values, and if so, what is the differential?

I would check to see if you have any sensor at your lower radiator hose, and if NOT, check the ACTUAL temperature at the ECTS housing (OFH) using an Infrared Thermometer, to see if it is within several degrees of the Temp Parameter your Scan Tool is reading.

In another thread, you said your engine could idle "for 1..2 hours and the temp never gets beyond 92--96 /197F..204F" so obviously the Fan IS coming on, but it may NOT ever run at as much as 50% (unless A/C on), but then you do NOT need A/C at the moment in Wellington.

You can download Bentley Service Manual in searchable pdf format here:
http://www.georgebelton.com/335i.tech/bentley.php

Here's what Bentley has to say about Inputs to the DME which it "sorts" to determine Fan Speed, and other Fan Trivia (170-3, p.356 of pdf):

Electric fan activation is based on the following inputs to the ECM:
• Radiator outlet temperature
• Calculated catalytic converter temperature
• Vehicle speed
• Battery voltage
• Calculated refrigerant pressure

When the vehicle is first started, the ECM activates the electric fan
briefly at 20% of its maximum speed, then switches OFF. This is for
diagnostic monitoring. The voltage generated by the fan when it
slows down (acting as a generator) must match the stored rpm
values in the fan output stage to confirm that the fan is operating
correctly.
NOTE-
• If the ECM fault memory indicates a cooling fan fault, check that the
fan is not seized and that it spins freely
• When A/C is switched ON, the electric fan is not immediately
turned on.
• After the engine is switched OFF, the fan may continue to run at
varying speeds for up to 10 minutes, based on calculated catalyst
temperature.

If your Fan "flunks" the Self-test described above, you should find BMW FC 2EFF saved in DME Fault Memory.

So if you have NO ROTS in your 335i, the primary input used by the DME to activate the fan is ECTS signal/ temp reported to DME, in conjunction with vehicle speed, and Refrigerant Pressure Sensor signal. As to the latter, when you turn on the A/C with the "snowflake" LED LIGHTED on right of A/C Control Panel, (to dehumidify, even if you don't need to cool the air ;-) the E-Fan should run @ ~ 50% speed at idle (heat transfer @ condenser).

Per your other thread, it would appear you have an intermittent fault in the ECTS or its associated connector/wiring.

Please let us know what you find,
George

[Abnob]

Hi, thanks for that response. Once I get my head around what everything means I will check it out. Yes, you are right we don't need an Aircon here just yet thanks again!!!