robertodonnell wrote: Dec 02, 2023 1:29 AM
Hi guys,
Can I ask everyone that's done this conversion, does the heater turn completely off when you turn the knob to cold after its been on heat? I rebuilt an OE valve, and it works fine on the bench, but still bleeds heat into the cabin if I've turned the heat up for a while. Thinking I was smart, I bought an Audi valve and fitted it today, and the brand new valve does the same thing!
...
Cheers,
Robert
Robert- it is my understanding that the heater valve opens and closes to admit hot water (coolant) into the heater core, so after heating for a while, the core is full of Hot Coolant.
Turning OFF the heat (closing the heater valve) will stop hot coolant from flowing into the core, but does NOT instantly cool anything... this takes time.
You don't 'turn off' a heater core that is filled with hot water, you stop water flowing through it. You can transfer more hot water into it; but after it's been heating, it remains hot for a bit. Thus, heat will continue to transfer to the air passing through the core... hence continued heating with the valve closed (knob turned all the way down).
Another car in our stable has a flapper door that shifts air flow from the heater core to the ducts - BYPASSING the core entirely. This results in a rapid cool air flow even after extended heating. It's a Japanese car, made in 1993, so I expect it to have more 'comfort features' than an E28. The air conditioner is similarly 'stupid;' as the temp control is moved off 'frigid' towards 'warm' the system gradually mixes Hot Air into the cold air stream, instead of the more efficient cycling of the A/C compressor on and off. But again, it's made in another country... not that there's anything wrong with that.
HTH
Andy