otter switch implementation? alternative?

[PierreW]

I’d like to know what this slot is for and why the thermal switch wasn't installed here instead of in the reservoir above the radiator. Wouldn't it be in more reliable contact with the coolant coming out of the engine here compared to its usual location? It seems like a useful alternative.

[mgcjag]

On previous/other models an ASC starter carb was used instead of the E type manual choke.....the otter switch that operated the ASC was mounted there......Jaguar obviously redesigned the system for the E type and though it better to have the fan otter switch in the header tank.....Steve

[PierreW]

That’s a strange line of reasoning from Jaguar... if the level drops (due to a leak), the sensor at the engine outlet will remain immersed in the flow as long as there is fluid in the radiator, whereas the one in the water tank will be dry—or nearly so.

[mgcjag]

You could redesign and fit your fan otter there if you prefer

[abowie]

You could redesign and fit your fan otter there if you prefer

As Steve says you can easily swap the placement of the otter switch. Personally I agree with you that's a better place for the switch anyway.