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bimmaster, BMW Technician
Category: BMW
Satisfied Customers: 1882
Experience:  3 years dealer experience, master bmw tech
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99 528i: Fault code..reads: coolant fan final stage..brand new

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Fault code on my '99 528i reads: "coolant fan final stage" The aux fan is brand new. This model doesn't have a risistor.
Hi, do you have a fault code number or P code?
Is the check engine light on?
Customer: replied 7 years ago.
7D, table 15 with Bavauto code reader. Engine light is on but also had fault with "SAP flow too low"
so don't know if light is on for the fan problem.
Hi, if the fan is working properly with the a/c on, and if it's very hot out, and running in traffic. I would ignore that fault code for now until the secondary air fault is rectified.

You will need to see if the air pump runs on cold start. then disconnect the hose to confirm the flow out of the pump is good, and the hose is in good shape, no leaks.
Then check to see if you have vacuum at the secondary air check valve when the pump is running. If not, then the vacuum line could be torn somewhere, just follow it back until you find a crack.

If all that is good, then the check valve is sticking, and should be replaced.

I have never seen a final stage fault code on these vehicles, and never seen one cause a check engine light. I think your problem lies in the secondary air system.
Customer: replied 7 years ago.
Does the aux fan come on when the coolant is getting too hot, or anytime the AC is on?
Yes thats correct, it should be on most of the time the a/c is on, or the compressor is engaged. It's also there to cool things down if coolant temp is too high.
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The final stage is an electrical device that controls the voltage to the aux fan.

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