1989 Bmw 535i Radiator Cooling Fan

[petersaaron30]

I have a e34 1989 Bmw 535i. Been working on the radiator cooling fan. I jumped the fan and it works. Relays and fuses are all good. Temperate sensor works. I cannot get the fan to kick on when car get hot. When I jump the wires at the temperture sensor the fan Will kick on.. I'm out of ideas. Thanks for the help

[theBMWbeast]

The auxiliary fan in front of the AC condenser is not for primary radiator cooling. That job is for the belt driven clutch fan, attached to the water pump pulley. The Aux fan comes on under two scenarios, AC button depressed (AC system in use), or before a major overheat. I am unsure on the temperature rating that is, but if your clutch fan is working properly, the aux fan should not kick on in normal operation. The clutch fan would keep the temperatures cool enough to be below that temperature switch for the aux fan.


If you perhaps do not have a belt driven fan, due to a previous owner, please advise.

[petersaaron30]

Thanks for the information didn't realize that.the temp Guage will go to 3/4.could the water pump be bad even though it not leaking.or guage reading bad.i have replaced thermostate

[royAdler]

+1 to theBMWBeast

The engine will need to get hot enough for the gage to read uncomfortably hot before the electric fan will come on.

You can go verify yourself, but if I recall the factory owners manual describes anything between the blue and the red on the gage as an acceptable temperature. I would be very uncomfortable with anything approaching the 3/4 mark or above, but I’m not a German engineer…

As to your comment about the wrong sensor, that can happen. There are two sensors, one for the dash gage, one for the DCM. They are not interchangeable in their output. If you or someone else installs the wrong sensor for the dash gage, it will read hot. I have made this mistake.

For a quick check get an IR temp gun and shoot all around the top of the thermostat housing looking for the hottest temp. I think I have notes from mine at ‘normal’ temp. If you like I can dig them up.

[shogun]

My aux fan did not start at high, after a long search I found out that the Hi speed relay pins were oxidized, spraying with contact cleaner and enhancer solved the problem.
On another car we found the same problem on the connector between fuse box and aux fan, exactly where it plugs into the aux fan, contact cleaner spray also helped there

[petersaaron30]

Thanks again will clean contacts