Aux fan won't come on

[Streichholzschächtelchen]

Having some strange problems with my 8i 325i vert. Aux fan won't turn on, here is what I have done so far.

Checked fuses 3, 19, and 20. All are good.

Checked K1, K6 relays, both are good.

I'm getting juice to pin 30 for both relays.

Running a tested, good temp sensor with the 3 prongs.

Fan works high and low speed when jumpered, so it isn't the fan stuck against it's shrowd or anything.

Radiator is hot as fuck along the length of the top, temp sensor is hot too.

When I hit the snowflake button (AC) the fan works. When I turn the snowflake button off it comes to a stop. Even at 3/4 temp the fan does nothing. My mechanical clutch fan is dead, so it's not like the mechanical fan is doing such a good job that the aux fan isn't needed. The engine gets hot.

Has a new, tested thermostat in it too, properly installed.

I really could use a little help with this.

[Streichholzschächtelchen]

Alright. i took apart the connector that goes on the temp sensor and put the high speed cable where the low speed was, and the low speed where the high was. My dad said in theory when the sensor clicks for low speed fan to turn on it will turn on the fan at hi speed, and if it actually reaches the point where high speed would normally turn on it will follow the path of least resistance, keeping the fan on high. Is this true? Now the fan doesn't turn on when I hit the snowflake, but the fan did turn on high when the needle reached half way between 3/4 and the beginning of the red zone. Good enough til tomorrow.

I think there might be a little air in the system. When does the low speed fan normally turn on in relation to the temp gauge?

[vpilarrt]

Low speed should come on at 91°C, probably just above half way on the gauge. May have air in the system. Your dad is wrong about the high speed following the path of least resistance. The fan speed is determined by which relay is closed, which powers the fan either thru the resistor (low speed) or non through the resistor (high speed).

[Streichholzschächtelchen]

So when the high speed relay clicks on the low speed clicks off then. Fosho, any way I can make it just high speed for both?

[vpilarrt]

No, the low speed doesn't switch off. When both circuits are on the fan will run in high speed because the non resistor circuit "over powers" the low speed circuit. The easiest way to make it run on high speed all the time is to remove the resistor and connect the 2 wires together.

[Streichholzschächtelchen]

Thanks bruddah