radiator and aux fan

[e30 dude]

83 320i - my radiator has no thermo switch(es) to operate the aux fan. so what controls the aux fan to turn on when needed?

[EverWiser]

It probably only operates when it gets a sig from the AC circuitry. If that's not it then I don't know...Sorry.

[e30 dude]

right now that's how it's set up. but i'm not sure if the aux fan is automatic, or in series with the AC blower. the aux fan comes on whenever i turn on the AC. i dont know if aux fan turns off when the compressor disengages though. so now i cant drive with the AC off, otherwise, the temp needles goes up.

[EverWiser]

If it's like an ex of mine's E34 it comes on when the AC high side pressure reaches a certain point. It helps cool the condensor and hence lowers the high side pressure back down below the "kick ON" point. On her car the pressure switch that caused this to happen was on the AC drier but I don't know about the E30, yet. Typically, going down the road, the aux fan will rarely have to kick on because of the air moving through the condensor. If your AC is non-functioning it's doubtful that the fan will ever kick on unless you hardwire it in some other manner.

[Ball325]

hmm so if my A/C is done, should I just remove it and the AUX Fan? I dont plan on fixing the AC any time soon.

[EverWiser]

You could always leave the aux fan and wire it to a switch for extra cooling in traffic. Just a thought.

[e30Matt]

Guys, just install the lower temp thermo switch if you're that set on deleting the engine driven fan. That way, the aux fan will automatically kick on at a lower temperature whether you have the A/C on or not.

Saves you the trouble of remembering to switch the A/C on and looking down, seeing your temp needle almost buried in the red on hot days.