The 603 engines also use the electric pusher fan(s) for the engine coolant, but only as a backup for the belt driven fan.

On 85 W123 sedans the relay lives under the black plastic cover on the driver's side wheel well. I would assume other W123 models would be similar.

-Jason

__________________
1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.