How to test if Auxiliary fan is bad?

rph74 · #1 06-13-2010, 04:27 PM

Is there a quick and easy test to see if the Auxiliary fan itself has gone bad? I checked and the fuse is fine.

The Aux. fan does not turn on when the AC is on. I probably shouldn't make such a big deal out of it, since my AC is still cool when stopped (most of the time). But I want my X5 running perfectly, and I don't want to spend $415 and a few hours of my time replacing the Auxiliary fan only to find out it was something else simple.

Thanks,

Chris

sic06 · #2 06-14-2010, 07:09 AM

prob. is- I just had to replace mine in my '06. I tried unplugging it and powering it from a external source, nothing. It was dead.

bimmerboy12 · #3 06-14-2010, 09:15 AM

not $415...

http://www.xoutpost.com/bmw-sav-foru...place-buy.html

urcbmw8 · #4 06-16-2010, 02:07 AM

I also have a bad ac fan on my 2001 X5 4.4i and I am wondering the AC fan or so called Auxilary fan has something to do with the main engine fan. I've been driven about one month now without AC fan because I don't use the AC. I may not need to replace it right now if I don't turn on AC. I just worry whether my car will be overheated if I drive in the hot summer days even though I don't turn on AC. Does anyone have any idea? So far, I've been driven without any problem at all and my temp guage remains staying in the middle. Please advise.

CharlieHustleX5 · #5 06-16-2010, 03:39 AM

The 2 fans are seperate.

The Aux. fan turns on when the AC is on full blast, if the car reaches higher temps towards 100 degrees celsius to aid in cooling the engine down, and under circumstances when instructed.

I've driven in SoCal heat for almost 2 summers without a working AUX fan. Just keep all cooling components in top condition, keep your coolant as fresh as factory suggests, and you should be fine. Thats all I've done.

n2red · #6 07-20-2010, 03:36 PM

Quote:

Originally Posted by CharlieHustleX5

The 2 fans are seperate.

The Aux. fan turns on when the AC is on full blast, if the car reaches higher temps towards 100 degrees celsius to aid in cooling the engine down, and under circumstances when instructed.

I've driven in SoCal heat for almost 2 summers without a working AUX fan. Just keep all cooling components in top condition, keep your coolant as fresh as factory suggests, and you should be fine. Thats all I've done.

The aux fan's primary job is to aid in the transfer of heat from the a/c condenser. While you may (or may not) notice a difference on the inside, the high side on your a/c system has to get well into the 200 range just to accomplish the job that would normally happen at 175/180 PSI.

For those that disable/remove their aux fan for whatever reason, you're really doing your a/c system a huge disservice.

Take a look at a large commercial building's air conditioning/refrigeration system. The condenser will always have a huge fan, and sometimes a water immersion system to coax the refrigerant back from a gas to a liquid. It doesn't matter if it's ammonia or R134. The science is the same.

The engine's operating temperature has no effect on this transformation.

CharlieHustleX5 · #7 07-20-2010, 05:59 PM

Quote:

Originally Posted by n2red

The aux fan's primary job is to aid in the transfer of heat from the a/c condenser. While you may (or may not) notice a difference on the inside, the high side on your a/c system has to get well into the 200 range just to accomplish the job that would normally happen at 175/180 PSI.

For those that disable/remove their aux fan for whatever reason, you're really doing your a/c system a huge disservice.

Take a look at a large commercial building's air conditioning/refrigeration system. The condenser will always have a huge fan, and sometimes a water immersion system to coax the refrigerant back from a gas to a liquid. It doesn't matter if it's ammonia or R134. The science is the same.

The engine's operating temperature has no effect on this transformation.

I understand the purpose of the aux fan and its importance to the AC system. I was not encouraging the disabling or removal of the fan all together. If you pay attention to the post before mine, urcbmw8 had stated :

"I've been driven about one month now without AC fan because I don't use the AC. I may not need to replace it right now if I don't turn on AC. I just worry whether my car will be overheated if I drive in the hot summer days even though I don't turn on AC. Does anyone have any idea?"

My response was to that question asked. In my situation, the Aux fan had died and I have not come around to replacing it. I did not use the AC as a result of that until the fan was replaced. Reading is fundamental...

For anyone who plans to use their AC on a regular basis, the aux fan cannot be ignored or removed. The fan is absolutely necessary to cool the condensor down while traveling at city speeds, sitting at idle, and when temperatures are high. I learned to drive with the windows open until the heat was too unbearable. Thats when I bit the bullet and replaced the fan assembly.

I agree with all your statements regarding AC systems and the need for a fan to aid in cooling the condensor.

Rockmelon · #8 07-21-2010, 04:24 AM

Quote:

Originally Posted by n2red

the high side on your a/c system has to get well into the 200 range just to accomplish the job that would normally happen at 175/180 PSI.

so the aux fan is triggered by the high side pressure? any idea how to increase the high pressure to get it to work most of the time or perhaps bypass the signal to keep the aux fan running all the time?

n2red · #9 07-21-2010, 09:47 AM

The aux fan is part of the overall a/c system. It isn't triggered by the high pressure side per se. When you turn on the a/c system, the aux fan turns on. It isn't "switchable" like turning on the fog lights to add more lighting.

The high pressure side of the a/c system isn't controlled by the driver. What the psi actual value is will be determined by the outside ambient temperature and the point at which the system can convert this refrigerant gas back into a liquid.

To give you some frame of reference.... on a properly operating system, at 70F, this conversion may be around 160 psi... at 90F, it may be 185 psi.

My point is.. (and I apologise for the wordiness...) on a properly maintained engine cooling system, the use, or requirement for, the aux fan to be needed to maintain engine cooling should not occur. No matter how how hot, gererally speaking, the outside temp is, the temp guage should hover right near the center of the dial. Use of the aux fan won't change this reading.

CharlieHustleX5 · #10 07-21-2010, 11:41 PM

Quote:

Originally Posted by n2red

My point is.. (and I apologise for the wordiness...) on a properly maintained engine cooling system, the use, or requirement for, the aux fan to be needed to maintain engine cooling should not occur. No matter how how hot, gererally speaking, the outside temp is, the temp guage should hover right near the center of the dial. Use of the aux fan won't change this reading.

Exactly what I was trying to assure urcbmw8 when I replied to his question. The AUX fan will turn on if engine temps reach approx. 120 degrees celcius. But on a maintained cooling system, the AUX fan will have no role in controlling engine temperature.