Aux. Fan Wiring on Radiator Temp Switch? [Archive] - Bimmerfest - BMW Forums

: Aux. Fan Wiring on Radiator Temp Switch?

11-15-2008, 06:29 PM
Hey guys, Having major dramas with a overheating issue on my 1989 535i. I've replaced the thermostat, water pump, coolant flush with heaps of bleeding, new fan clutch with new fan blades and the aux fan runs when the a/c is on. But when it's hot and the a/c is off the aux fan doesn't run. So I tested the switch at the radiator and when I jumped the wires the fan ran on low speed and high speed. So I just replaced the temp switch on the side of the radiator and as the connectors for that switch were perished I replaced them with new connectors as well. Plugged everything back in and the aux fan still doesn't run. I'm thinking that the wires are plugged in on the wrong terminals. On the switch there is an "O" , "1" , "2" next the the terminals. Which colour wires go on which terminal. I have brown, purple and yellow wires to choose from. I have tried different configerations to no avail. I've checked the fuses and relays and all is good. The temp is fine when driving but stuck in stop start traffic the temp rises to about 3/4 then once moving the temp drops back down to 1/2. As the aux fan runs when the a/c is on I've been driving around with it on and the temp still rises - but it shouldn't as all the fans etc. are running. Any ideas? Any help would be greatly appreciated. I'm tearing my hair out!

11-15-2008, 07:02 PM
Also forgot to mention that a new radiator and all hoses were replaces about 18 months ago and the air con has been serviced about a month ago with the new gas and a retrofit kit. Also the air con has gotten hotter too - must have a leak. Thanks guys.

bimmer dot info
11-17-2008, 06:42 AM
Try bleeding it some more. It can be a real pain to get all the air out of the system.

11-17-2008, 03:08 PM
No worries mate. I'll bleed it some more. Just to check - do you bleed it when it's hot and the thermostat is open? I've read differing opinions. Some say bleed it cold and some say bleed it hot.I've done it both ways and bleeding it when the motors running and when it's hot seems to be the most effective as getting air out. Is this correct?

bimmer dot info
11-18-2008, 06:20 AM
I usually do it when it is hot. It might help to try to bleed it cold and then hot.

Is part 9 the only bleeder on the 535i?

11-18-2008, 02:15 PM
Thanks Bimmer. I'll give it a go both ways. Yeah that is the only bleeder screw on the 535i.

11-25-2012, 11:23 AM
Hello there. I have an 89' 535i. I am having some issues with he cooling system. The car seems to maintain a good temperature while I am on the move. As soon as I hit stop and go traffic, then that is when my problems begin. I have replaced the thermostat, radiator, and water. I have not replaced the fan clutch. It seems to me that it is not working properly. Now I have the issue of the auxiliary cooling fan. It did not turn on at all. I did the jumper move and was able to get the low speed and high speed to come on. Therefore, my fan and circuits seem to be good. I then bought a brand new fan cooling fan switch that goes on the side of the radiator. Now, the aux fan does come on when the temperature reached the red. The thing that bothers me is that I only get the low speed to come on. The high speed activated by the switch is not working. I can swap the wires and successfully get the high speed to work. It seems that I can either get the low speed or high speed to work. I am assuming that the low speed will turn on after the temp will go a little above normal and then the high speed will kick in if the temperature continues to rise. This is not what is happening. Even after extreme overheating, the high speed does not kick in. Only the low speed.