A/C issues - AUX fan

[rdl]

To elaborate a bit on the outside ambient temperature sensor - not just plugged in, it has to be working properly with the instrument cluster indicating higher than 10C (~50F). So if the sensor, plug or wiring is damaged you'll get no joy on the aux fan.

BMW technical training documents are quite clear on this matter: if the HVAC panel doesn't sense over 10C it will not attempt to run A/C and thus the DME will not attempt to run the aux fan.

Geargrinder's comments about the aux fan are accurate. Contrary to some posts here & there, for the PWM fan the DME takes both A/C system pressure and radiator outlet temperature into account when deciding if or how fast to run the aux fan. Again BMW tech docs are explicit on this question.

[geargrinder]

The outside temp sensor HAS to work for the AC to turn on. Mandatory. You need to start with that first above all things. GG is 100% on the money with that.

My car is an 8/99 with the PWM fan which is shot, and my AC still works fine (I tend to use it mainly in low traffic conditions to keep the airflow over it, and I just replaced the aux fan in the X5 which whopped me for $375).

Get rid of that auc fault code as well, and things should run as normal.

To be fair - I wasn't one who brought it to the table, its been mentioned time and again but for some reason he keeps chasing something else.

Re: AUC error - both my cars have had AUC errors and run AC fine so I don't think that's required - that just hinders the auto-recirc pollution-sensor function.

[stiiaN]

Have you STILL not plugged in the outside temp sensor? You seem oddly dismissive and stubborn on that even though you've been told from way back that that was required for AC to be switched on.

Just plug it in, and ziptie it anyplace down there if your fender liner porkchop is damaged (I'm assuming this is why you aren't doing it properly once and for all). Please. Do it for the children. They are our future.

Here's what I think most likely happened: on that drive, engine temp rose high enough to require AUX fan on top of the visco mechanical fan, engine turned on AUX for a few minutes, engine temp cooled back down enough to not be required anymore, and shut fan off... and therefore, all that was unrelated to AC actuation whatsoever. To test that theory, you could thrash the heck out of the car for a short bit, and try to drive your engine temps as high as possible, then come to a hard stop, jump out and see if the fan has come back on again.

Also - you said "fan hitting something". Is your fan actually hitting something? The PWM fan might have an error condition sensing where it senses improper current draw or something if the fan is obstructed, and doesn't activate the fan if that happens. In fact on the M62TU I am pretty sure that logic is there - my fan once got frozen by snow-slush and I got a dashboard error about it.

However I am more likely thinking the issue is as above - AC isn't work cuz you still no plug in sensor, and this event was purely engine-temp related.

Okay I tried to plug it in, and yeah should have done it a while back......... But well it's dead.. So I'll have to get my hands on a new one.. Or used one..

But yeah I agree.. I guess the temps just went high enough.. First time tho.. And I tried to "trash" it a bit.. But I couldn't get it to turn on again.. As of now.
yeah it sounded like it was hitting the shroud a bit, somewhere.. But I'm not sure. Well it ran fine.. But I'll go through it anyway, so it won't hit it anymore.

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The outside temp sensor HAS to work for the AC to turn on. Mandatory. You need to start with that first above all things. GG is 100% on the money with that.

My car is an 8/99 with the PWM fan which is shot, and my AC still works fine (I tend to use it mainly in low traffic conditions to keep the airflow over it, and I just replaced the aux fan in the X5 which whopped me for $375).

Get rid of that auc fault code as well, and things should run as normal.

Okay... I'll have to get a new one. Because mine is dead.
Yeah I'll try try to get my hands on another AUC..

Thanks..

- - - Updated - - -

To elaborate a bit on the outside ambient temperature sensor - not just plugged in, it has to be working properly with the instrument cluster indicating higher than 10C (~50F). So if the sensor, plug or wiring is damaged you'll get no joy on the aux fan.

BMW technical training documents are quite clear on this matter: if the HVAC panel doesn't sense over 10C it will not attempt to run A/C and thus the DME will not attempt to run the aux fan.

Geargrinder's comments about the aux fan are accurate. Contrary to some posts here & there, for the PWM fan the DME takes both A/C system pressure and radiator outlet temperature into account when deciding if or how fast to run the aux fan. Again BMW tech docs are explicit on this question.

Yes okay.. Thanks for all this.. I'm sorry that I haven't done it before. But I'll get my hands on a new ambient temp sensor.

- - - Updated - - -

To be fair - I wasn't one who brought it to the table, its been mentioned time and again but for some reason he keeps chasing something else.

Re: AUC error - both my cars have had AUC errors and run AC fine so I don't think that's required - that just hinders the auto-recirc pollution-sensor function.

Yeas.. I've been chasing wild guesses.. And it has just wasted time. So I'll get a new one(used one). Thanks..