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Tonywa28 said:
Here's one technical update. I'm rethinking the auto thermostat switching. The problem I thought of was that if you're in bypass mode and you want to temper the AC output by adding in a bit of heat , you can't. You also couldn't run AC defrost and heat the car at the same time if the thermostat was tripped to switch the valve to bypass. So I think the final design is just going to be a 2-position switch that you set to bypass or not. The final design WILL incorporate the automatic return to the non-bypass mode when the ignition is turned off so the coolant pump circuit will operate as designed.
Tony
... probably a dumb question: rather than setting the bypass valve manually via a separate switch, couldn't this instead be activated automatically from the temperature control - i.e., heater bypassed when when temp switched to coldest setting regardless of whether AC is on or off?

-Chuck
 

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Tony, I suspect this may not be that simple. Air mixture flap is actuated by a stepper motor which I'm guessing is controlled by something other than a simple potentiometer. Unfortunately, what I know about stepper motors I can fit in a thimble and still have room for a bath. Any ee's out there?

-Chuck
 

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You're my hero!

I just knew you'd nail this, Tony. Congrats:clap:

Hope someone from Lotus is lurking.

-Chuck
 

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Tonywa28 said:
I looked for quite a while trying to find the normally closed switch in the counter-clockwise postion, but no luck. For me this would have been preferable to the push/pull version I was able to find. I'm sure it could be custom made, but at what price and how many. I was hoping by posting the need on the board maybe someone else knew of a source.

Tony
Another alternative to a push-pull switch (and one I think I'll try) is to add a SPDT relay to the standard rotory pot-switch combo which will activate the bypass when the switch is turned off (fully counter-clockwise to coldest). This does add about 1.25 oz. of weight, a couple bucks of expense and a little wiring complexity, but it makes cold air operation entirely intuitive (idiot-proof).

-Chuck
 
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