that control which resistor (resistors are R15 and R15/1) is in 'series' with the fan(s). The "logic" for this is deteremined by N22 as I told you when I answered your PM. This is the pushbutton unit located above the radio on the dash. The unit receives signals from the B12 (a/c pressure switch) and B10/8 (CTS sensor) and controls the starting point of the aux fans based on EITHER pressure with a/c or temperature (w/o a/c) in the engine coolant.

I think reference designators for the two relays are K9 and K9/1. If one is bad, that would explain why you had no low speed but had high. The table in my MENU #18 shows the switching points for either TEMP or PRESSURE.

__________________
Regards . . . . JimF
-------------------
'94 S500 Cpe

Visit my Mercedes Web Page