I can offer my slightly updated version for design and function of the 3.7 Roadster cooling system shown below if you wish Lorne?

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It appears it would suffer just as 3.0 Roadsters and other trads if air-con option was fitted and therefore benefit from the same cure. Important (maybe more than other models) that a three way valve is used though to maintain flow through heater pipes when matrix taken out of circuit. This would need to be fitted on heater inlet plumbing and require a second T junction to supplement the existing (41). A four way valve may offer a simpler plumbing solution, ideally a two state type rather than proportional control via rheostat. Either would work though with return flow maintained under all settings.

Richard

2018 Roadster 3.7
1966 Land Rover S2a 88
2024 Royal Enfield Guerrilla 450
1945 Guzzi Airone