On US left hand drive cars (probably similar RHD) there is a black 3 pin connector mounted above and behind the brake master cylinder. It has 3 wires black, red, and yellow that connect to the blower regulator. Disconnect and check for voltage on the yellow wire, body side, which is the control signal for the blower. If voltage is present (unlikely) its a control problem in the CCU or wiring to the regulator. If there is no control signal present then the regulator has failed and will need replaced (more likely). While expensive, considering replacing the blower motor too.

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90 300TE 4-M
Turbo 103, T3/T04E 50 trim
T04B cover .60 AR
Stage 3 turbine .63 AR
A2W I/C, 40 LB/HR
MS2E, 60-2 Direct Coil Control
3" Exh, AEM W/B O2
Underdrive Alt. and P/S Pulleys,
Vented Rear Discs, .034 Booster.
3.07 diffs 1st Gear Start

90 300CE 104.980
Milled & ported head, 10.3:1 compression
197° intake cam w/20° advancer
Tuned CIS ECU
4° ignition advance
PCS TCM2000, built 722.6
600W networked suction fan
Sportline sway bars
V8 rear subframe, Quaife ATB 3.06 diff