Finished at work a tad early today thus decided to "ular" after 4pm to workshop, eager to find out the irregular speed pattern of Aux Fan. Taken the first step in troubleshooting / problem isolation - to replace fan clutch.
Problem Description, Determination & Isolation
Round 1
1. Early morning during cold start, radiator fan shroud running, weak wind flow; aux fan idle. In contrast, 520i, strong wind generated at radiator fan.
2. Drive a little w/o A/C, halt, fan shroud running, aux fan start from slow then to medium speed. Observe water temp (KTMP)- 73C-78C, oil temp (OELTEMP) 75C-85C
3. Switch on A/C, both aux & electric fans maintain their speed. Observe KTMP - 80C-83C, OELTEMP 75C-85C
4. Off A/C and waited 10 minutes, both aux & electric fans maintain their speed.
5. Change fan clutch, stronger wind. Old fan clutch has obvious signs of oil leakage on both sides.
New fan clutch being taken out for replacement:
Left air intake duct removed to facilitate fan clutch replacement:
Round 2
1. At night, KTMP=70C, ignition, aux fan at medium speed & electric fans spinning
2. drive about 1km w/o A/C, KTMP=75-80C, while driving, heard aux fan switched to low speed or maybe even stopped.
3. Pull over, pop bonnet or hood if you wish, aux fan found stopped, start spinning low speed, stop, low speed, stop, low speed, switch on A/C, aux fan spins at medium speed. Off A/C, aux fan maintains medium speed after 5 minutes.
4. Close bonnet, drive home w/o A/C, aux fan stays medium speed. Off engine, aux fan stops, waited for a while, nothing happens.
After Round 1 and Round 2
1. FSU may not be faulty as after reading and researching a few threads, FSU faulty = aux fan continues to function after engine off.
2. Aux fan seems to turn at irregular speed, once speed increased to medium, apparently it doesn't slow down anymore, but never reached Hi speed so far.
3. Next item(s) to replace - external temperature sensor PN:65 81 6 905 133 {below (1)},
< your valuable suggestion here >,
< your valuable suggestion here >.
There are a few more temp sensors found while browsing the part list:
1. Electric parts automatic air condition Temperature sensor, heater 64 11 8 391 392
2. Cooling System Water Hoses Temperature sensor 13 62 1 433 077
Let's hope the aux fan could survive while I'm looking for solution to lessen its burden :4: