New cooling fan only turns on when AC is on.

[OnTheFence]

Old fan was dead.

Got brand new BMW fan.
This one only turns on when AC is on.
Fan turns on via the scan tool.

Otherwise, with AC off,
when engine gets up to temp,
EML light goes on, and fan does not turn on.

Any idea what is going on?

Is there a fuse I should check?
Or does fan on when AC is on mean fuse is good?

Can a relay be dead when the fan works when AC is on?
Anyone know where to find the relay part number?
https://www.realoem.com/bmw/enUS/partgrp?id=PC93-USA-01-2010-E83N-BMW-X3_30si&mg=17

[richardodn]

In the E83, fan speed is controlled by the DME using a PWM signal to the fan. There is no relay. Instead the connections are power, ground, & PWM. The DME makes its decisions based upon
Radiator outlet temperature
Calculated cat temperature
Vehicle speed
Battery voltage
Calculated refrigerant pressure

When the vehicle is first started, the DME will start the fan briefly at 20% and then monitor it as it spins down as a diagnostic check. Does this happen? Have you cleared any trouble codes?
Connections on the fan are
brown - ground
red/blue - 12V hot at all times
black/green - PWM control from DME

The fact that it turns on with AC on and from the scanner indicates power and ground are OK. The only thing I can think of is the fan is not responding to lower duty cycles. Does your scanner allow you to specify the duty cycle? I'm thinking that the default is 100% that the fan correctly responds to. However maybe it won't turn on at lower duty cycles. If you can't specify duty signal, maybe you can find a way to monitor the duty cycle of the control line and see if the DME is at least trying to turn it on.

[OnTheFence]

Conclusion:

A few ideas.

Since fan turns on via AC (and scan tool) then ECU driver works. Fan is getting signal.

Maybe scan tool may not be fully clearing code, and EML light may be triggered by old code. May need drive cycle to clear code. Don't 100% trust scanner? If "phantom" code, idling car in shop may not have reaching operating temps to turn on fan. Maybe that's why it seems fan is dead.

I suggested driving the car until full temp. Car won't overheat with dead fan since car moving and radiator is getting air flow. Drive cycle may clear code. And once temp is full, he can check if fan is on.

Also, just to be safe, first re-bleed via BMW procedure. 0) Remove coolant cap 1) Key ON. 2) Fan on. 3) Heat on HIGH. 4) Hold gas pedal for 15 seconds 5) Bleed should start.

Tomorrow, I think I will take it for a drive, and just make sure it does not over heat, go past vertical.
If it does not, I will try to get to 210F, and then come back to the shop, and then inspect the fan operation at full temp.

Went to the shop today.
Tried to check the coolant dipstick but could not remove the cap.
Hate that

Connected my C310 reader.
Cleared codes.

Set C310 to display live temp data.
Drove the car for 15-20 mins.
Temp needle went vertical and stayed there.
Temp ranged between 94 & 96C (201 & 205F)
Outside weather is 38F
So, WP/Tstat are working
Car is not overheating.
EML light did not come back on.

Tried to let car idle in driveway so fan would turn on, but temp would not go past 75 when idling.

X3 now has been driven for an hour drive with no issues, so that feels good.
Since I am operating at 94-96 (201-205F), and idle at 74C (165F), I need to watch the fan and catch it in action to put this to rest in my mind.
Next time I drive it, when I park, I will hop out and check the fan.