Aux Fan Question

I've noticed recently that it takes my aux fan takes a little while to kick on l, even when the a/c is on. It always comes on after I've driven it for a few minutes but when I first start it and get back out and watch it, with a/c on, it doesn't come on after a few minutes so I'll get out and drive it and 5-10 minutes later when I get to where I'm going it'll be running normally. When it does come on it'll switch between speeds normally. It comes on every time I drive I'm just not sure why it takes a while to come on even when the a/c is on from the time the car. Any help would be appreciated! Thanks!

Maybe your A/C pressure is a bit low that is why it takes a while to come on.
How is A/C system? Does it get cold?
What was the ambient temp when this happen?
Perhaps your A/C system has a very small leak.

The whole reason I've noticed this is because I've been working on my a/c system ever since it did get low. I've refilled it and now as of last night it sits at 45 psi when the fan is not running but when it finally kicks on it hovers around 32 psi. Ambient temp was 85. My air was also ice cold. Imma see how it does today in the 100 degree weather.

Your model year 528i (M52TU engine) aux fan operates differently than the earlier fans which come on as soon as the AC button is pressed. Your aux fan operates from a PWM signal from the ECM/DME...so don't have expectation for it to operate like the earlier fans that use an inline relay etc. See the info below:

Thanks guys! So should I be concerned if it eventually comes on and operates normally? The reason I'm asking is because when I leave my apartment I pull out onto a busy street with many lights so when I'm standing still in 100+ degree weather plus humidity it's not blowing very cold and my black car is burning hot until that fan decides to operate. Usually about 5-10 minutes into driving.

Originally Posted by blz456

Thanks guys! So should I be concerned if it eventually comes on and operates normally? The reason I'm asking is because when I leave my apartment I pull out onto a busy street with many lights so when I'm standing still in 100+ degree weather plus humidity it's not blowing very cold and my black car is burning hot until that fan decides to operate. Usually about 5-10 minutes into driving.

E39 A/C service is very finicky and you must know know what you're doing when it comes to how much Freon is allowed. I heard it goes by weight not pressure.

It sounds to me your A/C is not right, it should gets cold instantly in 30 seconds not 5-10 minutes later.
I don't think it will further damage the way it is, but if it is up to me I have it fix.

Yeah... I am definitely going to keep working on it because a/c is an absolute must here in Mississippi. When the fan works it's ice cold but maybe something is not right with the freon causing the delay of the fan starting. Anyone know of a correct way to do this that I can DIY? Not just simple pressure measuring.