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Old 04-16-2022, 05:06 PM
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andrewwynn andrewwynn is offline
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Location: Racine, WI
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2005 X5 4.4 can I force the electric cooling/radiator fan to be on?

You cannot Hotwire the aux fan to airways run as it runs from a PWM signal. (I mean people *have* made PWM signal).

A few things;

1) if you can't set the HVAC blower to any speed the FSU is shot

2) the aux fan will come on at a lower temp when AC is engaged (or would never get AC at a stop light)

3) unplugging the ac pressure sensor should engage the aux fan it's the main way people test it

4) if the aux fan fails self test at start, the AC won't run. It is possible for the fan to pass the test but not work, no idea how but I've seen it.

4.5) if ac doesn't run, aux fan often won't kick on because the couch fan does a good enough job.

5) the clutch fan should keep the car from overheating other than extended period of idle even at 120F. 220-120=100, 220-90=130. it's only 30% different between 90 and 120 ambient.

6) the best way to clean the interior temp sensor vent is a gum proxabrush (mini toothbrush for between teeth). Also the best tool to clean a phone charging port!

7) the temp indicator on the dash is not a thermometer unfortunately. Itt points straight up over about a 40C range is temp! Think of it as a trinary indicator 1) starting to warm up 2) mostly warm but no guarantee at operating temp 3) overheated, turn off engine immediately or warp your head.

Learn to use the hidden menu you can see the real-time coolant temps and see what I mean.

Even with the AC on, it's normal for the aux fan (at radiator) to not run unless you are not moving. Usually 5-8 minutes of idling when ambient is high like 100 will be enough to get aux fan to kick on.

You should also see it twitch at start: have somebody else start the car while you are watching the aux fan. It should move a few degrees and stop. Part of the startup self test.
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2011 E70 N55 (me)
2012 E70 N63 (wife)

Last edited by andrewwynn; 04-16-2022 at 05:16 PM.
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