Steve I don't know if this is of any help but I got irritated with the fluctuating temperature outlet of my heater when I had it on during cold summer nights etc. Suddenly it was 40°C in the cockpit and 2 minutes later 18°C all depending on engine rpm and available flow for the heater core.
So I installed a dedicated heater pump like we know from all modern cars and it is switched via a micro switch on the cable/valve assembly so when the temp selector on the dash is all the way left the power to the pump is cut and the pump stops. It works quite nice so now we are able to control the temp in the cockpit much better.
BTW the temporary cable tie is now replaced with a proper clamp.
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