Go Back   United Bimmer Community - BMW Forum > UnitedBimmer- Model Categories > 5-Series > E12, E28, E34, E39, E60
FAQ Members List Calendar Advertise With Us Mark Forums Read

E12, E28, E34, E39, E60 General discussion and technical help for all year 5 series cars.

Reply
 
Thread Tools
Old 08-18-2010, 02:33 PM   #1
tm11nia

Name: tm11nia
Title: United Newb
Status: Offline
Join Date: Aug 2010
Location: Romania
User not setup in Rate My Car.
Click here to set it up.
Your Ride: e39 523i 1996
aux A/C fan problems

3 years ago when I bought my 523i '96 it had problems with A/C. In hot weather ~38 degree C if A/C turned on, the temp. gauge started indicating temps close to 120 degrees... there was no way to keep A/C on. In our own workshop (since I work as a auto parts salesman) they managed to get the auxiliary A/C fan to start, and even first and second stage running... Later I learned that in fact second and third stage were merged together electricaly... It worked that way for a couple of years untill the aux A/C fan motor died (three of the six magnets inside the motor got unglued and ended up grinding against the rotor, causing huge current consumption and eventualy blowing all the fuses that govern the three stages of the aux A/C fan). Having the motor replaced with a used one, together with the resistor assy, I observed that only (I guess) the second speed stage is active. The mannifestation of that fact is that the aux fan starts at about 94 degree engine core temp, runs for about 10-15 secs and shuts off for about 20-30 secs...
The normal way of operation would be that the first stage starts at 94, runs for all the A/C on period in silent manner, the second stage active at temps above 104 engine core degrees, and the third stage kicks in in extreme conditions such as very hot outside temp, towing or climbing very stiff roads...
Since the thermostat keeps the engine at 95 degrees, the first speed stage of the aux fan is supposed to run as long as the A/C is turned on...
Before replacing the aux fan motor, the engine core temp in summer conditions was allmost allways close to 100 degrees. That was (I'm sure) beacause of the fact that the A/C condenser wich is placed in front of the radiator was full of dirth that calcified in the cooling cells over the years, and not enough fresh air got through to the engine radiator....Nevertheless, behind the aux fan motor and behind the supporting frame of the aux fan assy, the clogging was total so I guess about 50% of the normal fresh air amount was getting to the engine radiator causing the viscous coupling to spin excessively and sound as a jet plane...
Today I got the wiring diags for the aux A/C fan and figured out what could be the cause of missing first and third speed stage.
The results of faulty aux fan operation are poor refrigerant efficiency and ineffective cooling of the engine.
Thank you. I expect opinions.
  Reply With Quote
Old 08-20-2010, 01:25 AM   #2
armandjones82

Name: armandjones82
Title: Read Only Club
Status: Offline
Join Date: Aug 2010
Location: Missouri
User not setup in Rate My Car.
Click here to set it up.
Your Ride: Toyota Prius
That's a nice post about what you have experience regarding the auxiliary fan problem. It gives me a good knowledge, since you are a car parts sales man. It was very good of you to explain that one and I appreciate it for me to learn something more. Keep it up!
  Reply With Quote
Old 08-20-2010, 02:14 PM   #3
tm11nia

Name: tm11nia
Title: United Newb
Status: Offline
Join Date: Aug 2010
Location: Romania
User not setup in Rate My Car.
Click here to set it up.
Your Ride: e39 523i 1996
Thank you! I'm glad that my expertise was helpfull.
Anyway, as I mentioned in my previous post, I TOUGHT that I figured out what is wrong. In fact the problem was a bit different.... After checking again the fuses behind the glowe compartment (f7, f20, f22 and f75) I was surprised that none of them was in fact blown. Before I go on with the article, I must say at risk of sounding silly, that like many other electrical systems, my car allso must have a daemon within the wires.... Last summer, a day before taking a 2 weeks vacation in Germany ( max. speeds under 210 km/h in Germany, alltough my wife did not even noticed that while reading a book...), the Aircon stopped blowing cold air. The solution was quickly found by our workshop electrician: the f22 fuse blown. At that time the aux fan was the old one wich recently died. For the next year and until the other weekend when again I had to take a 2 days vacation, the A/C system performed fairly. Half an hour before having to leave the city with my family, the f22 fuse blew. That is why I suspect the car has its moods...
Ok, we took the trip, went back and after 2-3 days the aux fan died for good (fuse blown again). After a few calls, I got a used aux fan for about 45€. Unfortunately in the process of replacing it with my old fan, one of the wires coming out of the 2nd stage resistor got broken and I had to use the resistor out of my old fan assy. Funny thing is that out of two identical resistors I chose the one that (did not know till yesterday) was broken or burned or dead. Before deciding to jump it with an 2.5mm wire I took out the socket out of the thermoswitch and fooled the car into believing that the coolant had 94 deg by jumping ground with 2nd stage line, respectively 104 deg by jumping the GND with the 3rd stage line using a 10 cm long wire. The only reaction was that third stage fan speed was working since it goes directly to the fan motor and does not go through the two resistors. Since those (resistors) are serially connected, the logical conclusion was that the resistor next to the fan motor is faulty. That was the case in reality when I measured its resistance. Soon I will again strip the car off its bumper, headlights, air guides and manny other parts in order to replace the resistor. After that I expect no other difficultyes and all three stages of the aux fan to run as intended by the Bavarian manufacturer...

Last edited by tm11nia; 08-20-2010 at 02:16 PM..
  Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
E36 fan delete mod and now aux. fan does not work fxoaxaca E36 2 08-14-2010 01:04 AM
Aux fan relay stevieL 7 Series (E23, E32, E38, E65, E66) 0 01-30-2010 02:50 PM
help with A/C and AUX fan eightynine535 E12, E28, E34, E39, E60 14 08-28-2007 09:57 PM
aux fan nij E12, E28, E34, E39, E60 2 04-01-2007 04:54 PM
A/C Problem -Aux fan stops Siaren Z Series (Z3, Z4, Z8) 11 05-17-2006 10:03 AM


All times are GMT -5. The time now is 06:53 AM.

A vBSkinworks Design

 
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Copyright © 2005-2013 UnitedBimmer.com