Sorry to bug everyone with this but I have done extensive research on this site and others and can't find the answer on this.

1990 300SL M104

I've replaced the ECT sensor and added JimF's resistor mod. The Aux fans turn on high at about 105c. They do not turn on low with an increase in temperature.

I've had the relay apart (its a double relay affair) and can trigger low and high speeds manually.

My refridgerant is low (another project) but I can trigger low speed fans by pulling the A/C pressure sensor leads and jumping them (the compressor also engages)

Should the aux fans engage at low speed based on temp change on this model? If so, what would be the next thing on the list to check?

Many thanks to JimF, Bobterry et al.