Air con blower stopped working

The two fans in the ventilation system on my 1984 HE suddenly stopped working completely without warning, on a hot summer day, of course. I have checked the following. All fuses are OK. compressor runs and cools as it should. When I move the thermostat potentiometer and fan switch I can hear that vacuum-controlled air clamps work so that part is probably also in order. I also check 4 double relays at the feet on the left side (LHD) and all 4 relays work as they should. I have run out of further ideas. is there a wise head who can help me!?!?

There is a thermostatic switch at the input of the heater core that disables the fans until the engine warms a little. Its behind the left hand side lower console cover. Just connect the two cables together and see if the fans would work.